Merge pull request #20419 from keszybz/setenv-no-value

[thirdparty/systemd.git] / TODO

Bugfixes:

* Many manager configuration settings that are only applicable to user
  manager or system manager can be always set. It would be better to reject
  them when parsing config.

* userdbctl: "Password OK: yes" is shown even when there are no passwords
  or the password is locked.

* Get rid of nftw(). We should refuse to use such useless APIs on principle.

* Jun 01 09:43:02 krowka systemd[1]: Unit user@1000.service has alias user@.service.
  Jun 01 09:43:02 krowka systemd[1]: Unit user@6.service has alias user@.service.
  Jun 01 09:43:02 krowka systemd[1]: Unit user-runtime-dir@6.service has alias user-runtime-dir@.service.

External:

* Fedora: add an rpmlint check that verifies that all unit files in the RPM are listed in %systemd_post macros.

* dbus:
   - natively watch for dbus-*.service symlinks (PENDING)
   - teach dbus to activate all services it finds in /etc/systemd/services/org-*.service

* kernel: add device_type = "fb", "fbcon" to class "graphics"

* /usr/bin/service should actually show the new command line

* fedora: suggest auto-restart on failure, but not on success and not on coredump. also, ask people to think about changing the start limit logic. Also point people to RestartPreventExitStatus=, SuccessExitStatus=

* neither pkexec nor sudo initialize environ[] from the PAM environment?

* fedora: update policy to declare access mode and ownership of unit files to root:root 0644, and add an rpmlint check for it

* register catalog database signature as file magic

* zsh shell completion:
  - <command> <verb> -<TAB> should complete options, but currently does not
  - systemctl add-wants,add-requires

* systemctl status should know about 'systemd-analyze calendar ... --iterations='
* If timer has just OnInactiveSec=..., it should fire after a specified time
  after being started.

* write blog stories about:
  - hwdb: what belongs into it, lsusb
  - enabling dbus services
  - how to make changes to sysctl and sysfs attributes
  - remote access
  - how to pass throw-away units to systemd, or dynamically change properties of existing units
  - testing with Harald's awesome test kit
  - auto-restart
  - how to develop against journal browsing APIs
  - the journal HTTP iface
  - non-cgroup resource management
  - dynamic resource management with cgroups
  - refreshed, longer missions statement
  - calendar time events
  - init=/bin/sh vs. "emergency" mode, vs. "rescue" mode, vs. "multi-user" mode, vs. "graphical" mode, and the debug shell
  - how to create your own target
  - instantiated apache, dovecot and so on
  - hooking a script into various stages of shutdown/rearly booot

Regularly:

* look for close() vs. close_nointr() vs. close_nointr_nofail()

* check for strerror(r) instead of strerror(-r)

* pahole

* set_put(), hashmap_put() return values check. i.e. == 0 does not free()!

* use secure_getenv() instead of getenv() where appropriate

* link up selected blog stories from man pages and unit files Documentation= fields

Janitorial Clean-ups:

* Rearrange tests so that the various test-xyz.c match a specific src/basic/xyz.c again

* rework mount.c and swap.c to follow proper state enumeration/deserialization
  semantics, like we do for device.c now

Features:

* tpm2: figure out if we need to do anything for TPM2 parameter encryption? And
  if so, what precisely?

* insert pkcs7 signature for verity gpt

* when mounting disk images: if IMAGE_ID/IMAGE_VERSION is set in os-release
  data in the image, make sure the image filename actually matches this, so
  that images cannot be misused.

* use credentials logic/TPM2 logic to store homed signing key

* New udev block device symlink names:
  /dev/disk/by-parttypelabel/<pttype>/<ptlabel>. Use case: if pt label is used
  as partition image version string, this is a safe way to reference a specific
  version of a specific partition type, in particular where related partitions
  are processed (e.g. verity + rootfs both named "LennartOS_0.7").

* in sd-id128: also parse UUIDs in RFC4122 URN syntax (i.e. chop off urn:uuid: prefix)

* DynamicUser= + StateDirectory= → use uid mapping mounts, too, in order to
  make dirs appear under right UID.

* systemd-sysext: optionally, run it in initrd already, before transitioning
  into host, to open up possibility for services shipped like that.

* maybe add a tool that displays most recent journal logs as QR code to scan
  off screen and run it automatically on boot failures, emergency logs and
  such. Use DRM APIs directly, see
  https://github.com/dvdhrm/docs/blob/master/drm-howto/modeset.c for an example
  for doing that.

* pass systemd-detect-virt result to generators as env var. Modifying behaviour
  based on whether we are virtualized or not is a pretty common thing, hence
  maybe just pass that info along for free in an env var. We cache the result
  anyway, so it's basically free.

* introduce /dev/disk/root/* symlinks that allow referencing partitions on the
  disk the rootfs is on in a reasonably secure way. (or maybe: add
  /dev/gpt-auto-{home,srv,boot,…} similar in style to /dev/gpt-auto-root as we
  already have it.

* whenever we receive fds via SCM_RIGHTS make sure none got dropped due to the
  reception limit the kernel silently enforces.

* add an Open= setting to service unit files that can open arbitrary file
  system paths at service startup time and pass them to the service process via
  our usual socket activation protocol. If passed path refers to AF_UNIX
  socket: connect() to it.

* add a ConnectSocket= setting to service unit files, that may reference a
  socket unit, and which will connect to the socket defined therein, and pass
  the resulting fd to the service program via socket activation proto.

* Add a concept of ListenStream=anonymous to socket units: listen on a socket
  that is deleted in the fs. Usecase would be with ConnectSocket= above.

* importd: support image signature verification with PKCS#7 + OpenBSD signify
  logic, as alternative to crummy gpg

* sysext: optionally, if the merged trees allow it use bind mounts instead of
  overlayfs

* add "systemd-analyze debug" + AttachDebugger= in unit files: The former
  specifies a command to execute; the latter specifies that an already running
  "systemd-analyze debug" instance shall be contacted and execution paused
  until it gives an OK. That way, tools like gdb or strace can be safely be
  invoked on processes forked off PID 1.

* expose MS_NOSYMFOLLOW in various places

* allow passing creds into kernel when booting: in EFI stub, collect creds
  files from ESP directory, generate CPIO archive on the fly from them, so that
  they are dropped into /run/initramfs/creds/ and pass to kernel as additional
  initrd. Then, use LoadCredentialEncrypted=foo:/run/initramfs/creds/foo to
  load them.

* make LoadCredential= automatically find credentials in /etc/creds,
  /run/creds, … and so on, if path component is unqualified

* teach LoadCredential=/LoadCredentialEncrypted= to load credentials from
  kernel cmdline, maybe: LoadCredentialEncrypted=foobar:proc-cmdline:foobar

* credentials system:
  - acquire from kernel command line
  - acquire from EFI variable?
  - acquire via via ask-password?
  - acquire creds via keyring?
  - pass creds via keyring?
  - pass creds via memfd?
  - acquire + decrypt creds from pkcs11?
  - make systemd-cryptsetup acquire pw via creds logic
  - make PAMName= acquire pw via creds logic
  - make macsec/wireguard code in networkd read key via creds logic
  - make gatwayd/remote read key via creds logic
  - add sd_notify() command for flushing out creds not needed anymore

* teach LoadCredential= the ability to load all files from a specified dir as
  individual creds

* add tpm.target or so which is delayed until TPM2 device showed up in case
  firmware indicates there is one.

* tpm2: support a PIN policy, i.e. allowing windows-style short authentication
  passwords by using the TPM2 to enforce ratelimiting and such, use for
  cryptsetup and homed

* Add concept for upgrading TPM2 enrollments, maybe a new switch
  --pcrs=4:<hash> or so, i.e. select a PCR to include in the hash, and then
  override its hash

* TPM2: auto-reenroll in cryptsetup, as fallback for hosed firmware upgrades
  and such

* introduce a new group to own TPM devices

* cryptenroll: politely refuse enrolling new keys to homed volumes, since we
  we cannot update identity info

* cryptsetup: if only recovery keys are registered and no regular passphrases,
  ask user for "recovery key", not "passphrase"

* cyptsetup: add option for automatically removing empty password slot on boot

* cryptsetup: optionally, when run during boot-up and password is never
  entered, and we are on battery power (or so), power off machine again

* cryptsetup: when FIDO2/PKCS#11/TPM2 token/chip didn't show up after some
  time, abort the attempt, fallback to asking for pw

* cryptsetup: when waiting for FIDO2/PKCS#11 token, tell plymouth that, and
  allow plymouth to abort the waiting and enter pw instead

* make cryptsetup lower --iter-time

* cryptsetup: allow encoding key directly in /etc/crypttab, maybe with a
  "base64:" prefix. Useful in particular for pkcs11 mode.

* cryptsetup: reimplement the mkswap/mke2fs in cryptsetup-generator to use
  systemd-makefs.service instead.

* cryptsetup:
  - cryptsetup-generator: allow specification of passwords in crypttab itself
  - support rd.luks.allow-discards= kernel cmdline params in cryptsetup generator

* when configuring loopback netif, and it fails due to EPERM, eat up error if
  it happens to be set up alright already.

* at boot: check if battery above some threshold, if not power off again after explanation

* userdb: add field for ambient caps, so that a user can have CAP_WAKE_ALARM
  for example. And add code that resets ambient caps for all services by
  default.

* sd-bus: when connecting to some dbus server socker, set originating AF_UNIX
  socket name in abstract namespace to include "description" string, and pick
  it up from there in sd_bus_creds logic. i.e. we can use the socket peer
  address as conduit for some minimal connection metainfo, and use it to
  restore the "description" logic that kdbus used to have.

* systemd-analyze netif that explains predictable interface (or networkctl)

* Add service setting to run a service within the specified VRF. i.e. do the
  equivalent of "ip vrf exec".

* change SwitchRoot() implementation in PID 1 to use pivot_root(".", "."), as
  documented in the pivot_root(2) man page, so that we can drop the /oldroot
  temporary dir.

* special case some calls of chase_symlinks() to use openat2() internally, so
  that the kernel does what we otherwise do.

* make use of new glibc 2.32 APIs sigabbrev_np() and strerrorname_np().

* add /etc/integritytab, to support dm-integrity setups. In particular those
  with HMAC as hash function, so that we can have a protected /home without
  encryption (leaving encryption to the individual dirs/homed).

* complement root=, rootflags=, rootfstype= with rootsubdir= which allows
  mounting a subdir of the root fs as actual root. This can be used as
  fstype-agnostic version of btrfs' rootflags=subvol=foobar.

* if /usr/bin/swapoff fails due to OOM, log a friendly explanatory message about it

* Remove any support for booting without /usr pre-mounted in the initrd entirely.
  Update INITRD_INTERFACE.md accordingly.

* pid1: Move to tracking of main pid/control pid of units per pidfd

* pid1: support new clone3() fork-into-cgroup feature

* pid1: support new cgroup.kill to terminate all processes in a cgroup

* pid1: also remove PID files of a service when the service starts, not just
  when it exits

* make us use dynamically fewer deps for containers in general purpose distros:
  o turn into dlopen() deps:
    - elfutils (always)
    - p11-kit-trust (always)
    - kmod-libs (only when called from PID 1)
    - libblkid (only in RootImage= handling in PID 1, but not elsewhere)
    - libpam (only when called from PID 1)
    - bzip2, xz, lz4 (always — gzip and zstd should probably stay static deps the way they are,
      since they are so basic and our defaults)
  o move into separate libsystemd-shared-iptables.so .so
    - iptables-libs (only used by nspawn + networkd)

* seccomp: maybe use seccomp_merge() to merge our filters per-arch if we can.
  Apparently kernel performance is much better with fewer larger seccomp
  filters than with more smaller seccomp filters.

* systemd-path: add ESP and XBOOTLDR path. Add "private" runtime/state/cache dir enum,
  mapping to $RUNTIME_DIRECTORY, $STATE_DIRECTORY and such

* All tools that support --root= should also learn --image= so that they can
  operate on disk images directly. Specifically: bootctl, systemctl,
  coredumpctl. (Already done: systemd-nspawn, systemd-firstboot,
  systemd-repart, systemd-tmpfiles, systemd-sysusers, journalctl)

* seccomp: by default mask x32 ABI system wide on x86-64. it's on its way out

* seccomp: don't install filters for ABIs that are masked anyway for the
  specific service

* seccomp: maybe merge all filters we install into one with that libseccomp API that allows merging.

* busctl: maybe expose a verb "ping" for pinging a dbus service to see if it
  exists and responds.

* Maybe add a separate GPT partition type to the discoverable partition spec
  for "hibernate" partitions, that are exactly like swap partitions but only
  activated right before hibernation and thus never used for regular swapping.

* by default, in systemd --user service bump the OOMAdjust to 100, as privs
  allow so that systemd survives

* socket units: allow creating a udev monitor socket with ListenDevices= or so,
  with matches, then activate app through that passing socket over

* unify on openssl (as soon as OpenSSL 3.0 is out, and the Debian license
  confusion is gone)
  - port sd_id128_get_machine_app_specific() over from khash
  - port resolved over from libgcrypt (DNSSEC code)
  - port journald + fsprg over from libgcrypt
  - port importd over from libgcrypt
  - when that's done: kill khash.c
  - when that's done: kill gnutls support in resolved

* add growvol and makevol options for /etc/crypttab, similar to
  x-systemd.growfs and x-systemd-makefs.

* userdb: allow username prefix searches in varlink API, allow realname and
  realname substr searches in varlink API

* userdb: allow uid/gid range checks

* userdb: allow existence checks

* pid1: activation by journal search expression

* when switching root from initrd to host, set the machine_id env var so that
  if the host has no machine ID set yet we continue to use the random one the
  initrd had set.

* sd-event: add native support for P_ALL waitid() watching, then move PID 1 to
  it for reaping assigned but unknown children. This needs to some special care
  to operate somewhat sensibly in light of priorities: P_ALL will return
  arbitrary processes, regardless of the priority we want to watch them with,
  hence on each event loop iteration check all processes which we shall watch
  with higher prio explicitly, and then watch the entire rest with P_ALL.

* tweak sd-event's child watching: keep a prioq of children to watch and use
  waitid() only on the children with the highest priority until one is waitable
  and ignore all lower-prio ones from that point on

* maybe introduce xattrs that can be set on the root dir of the root fs
  partition that declare the volatility mode to use the image in. Previously I
  thought marking this via GPT partition flags but that's not ideal since
  that's outside of the LUKS encryption/verity verification, and we probably
  shouldn't operate in a volatile mode unless we got told so from a trusted
  source.

* coredump: maybe when coredumping read a new xattr from /proc/$PID/exe that
  may be used to mark a whole binary as non-coredumpable. Would fix:
  https://bugs.freedesktop.org/show_bug.cgi?id=69447

* teach parse_timestamp() timezones like the calendar spec already knows it

* beef up hibernation to optionally do swapon/swapoff immediately before/after
  the hibernation

* beef up s2h to implement a battery watch loop: instead of entering
  hibernation unconditionally after coming back from resume make a decision
  based on the battery load level: if battery level is above a specific
  threshold, go to suspend again, only hibernate if below it. This means we'd
  stick to suspend usually, but fall back to hibernation only when battery runs
  empty (well, subject to our sampling interval). Related to this, check if we
  can make ACPI _BTP (i.e. /sys/class/power_supply/*/alarm) work for us too,
  i.e. see if it can wake up machines from suspend, so that we could resume
  automatically when the system is low on power and move automatically to
  hibernation mode. (see
  https://uefi.org/sites/default/files/resources/ACPI%206_2_A_Sept29.pdf
  section 10.2.2.8 and
  https://docs.microsoft.com/en-us/windows-hardware/design/device-experiences/modern-standby-wake-sources
  at the end).

* We should probably replace /etc/rc.d/README with a symlink to doc
  content. After all it is constant vendor data.

* maybe add kernel cmdline params: to force random seed crediting

* introduce a new per-process uuid, similar to the boot id, the machine id, the
  invocation id, that is derived from process creds, specifically a hashed
  combination of AT_RANDOM + getpid() + the starttime from
  /proc/self/status. Then add these ids implicitly when logging. Deriving this
  uuid from these three things has the benefit that it can be derived easily
  from /proc/$PID/ in a stable, and unique way that changes on both fork() and
  exec().

* let's not GC a unit while its ratelimits are still pending

* when killing due to service watchdog timeout maybe detect whether target
  process is under ptracing and then log loudly and continue instead.

* make rfkill uaccess controllable by default, i.e. steal rule from
  gnome-bluetooth and friends

* make MAINPID= message reception checks even stricter: if service uses User=,
  then check sending UID and ignore message if it doesn't match the user or
  root.

* maybe trigger a uevent "change" on a device if "systemctl reload xyz.device"
  is issued.

* when importing an fs tree with machined, optionally apply userns-rec-chown

* when importing an fs tree with machined, complain if image is not an OS

* Maybe introduce a helper safe_exec() or so, which is to execve() which
  safe_fork() is to fork(). And then make revert the RLIMIT_NOFILE soft limit
  to 1K implicitly, unless explicitly opted-out.

* rework seccomp/nnp logic that even if User= is used in combination with
  a seccomp option we don't have to set NNP. For that, change uid first whil
  keeping CAP_SYS_ADMIN, then apply seccomp, the drop cap.

* when no locale is configured, default to UEFI's PlatformLang variable

* add a new syscall group "@esoteric" for more esoteric stuff such as bpf() and
  usefaultd() and make systemd-analyze check for it.

* paranoia: whenever we process passwords, call mlock() on the memory
  first. i.e. look for all places we use free_and_erasep() and
  augment them with mlock(). Also use MADV_DONTDUMP.
  Alternatively (preferably?) use memfd_secret().

* Move RestrictAddressFamily= to the new cgroup create socket

* support the bind/connect/sendmsg cgroup stuff for sandboxing, and possibly
  patching around

* maybe implicitly attach monotonic+realtime timestamps to outgoing messages in
  log.c and sd-journal-send

* optionally: turn on cgroup delegation for per-session scope units

* introduce per-unit (i.e. per-slice, per-service) journal log size limits.

* sd-boot: automatically load EFI modules from some drop-in dir, so that people
  can add in file system drivers and such

* sd-boot: optionally, show boot menu when previous default boot item has
  non-zero "tries done" count

* augment CODE_FILE=, CODE_LINE= with something like CODE_BASE= or so which
  contains some identifier for the project, which allows us to include
  clickable links to source files generating these log messages. The identifier
  could be some abberviated URL prefix or so (taking inspiration from Go
  imports). For example, for systemd we could use
  CODE_BASE=github.com/systemd/systemd/blob/98b0b1123cc or so which is
  sufficient to build a link by prefixing "http://" and suffixing the
  CODE_FILE.

* Augment MESSAGE_ID with MESSAGE_BASE, in a similar fashion so that we can
  make clickable links from log messages carrying a MESSAGE_ID, that lead to
  some explanatory text online.

* maybe extend .path units to expose fanotify() per-mount change events

* When reloading configuration PID 1 should reset all its properties to the
  original defaults before calling parse_config()

* hibernate/s2h: make this robust and safe to enable in Fedora by default.
  Specifically:

  1. add resume_offset support to the resume code (i.e. support swap files
     properly)
  2. check if swap is on weird storage and refuse if so
  3. add auto-detection of hibernation images

* cgroups: use inotify to get notified when somebody else modifies cgroups
  owned by us, then log a friendly warning.

* beef up log.c with support for stripping ANSI sequences from strings, so that
  it is OK to include them in log strings. This would be particularly useful so
  that our log messages could contain clickable links for example for unit
  files and suchlike we operate on.

* importd: add ability download images for portabled + sysext

* add support for "portablectl attach http://foobar.com/waaa.raw (i.e. importd integration)

* sync dynamic uids/gids between host+portable srvice (i.e. if DynamicUser=1 is set for a service, make sure that the
  selected user is resolvable in the service even if it ships its own /etc/passwd)

* Fix DECIMAL_STR_MAX or DECIMAL_STR_WIDTH. One includes a trailing NUL, the
  other doesn't. What a disaster. Probably to exclude it. Also
  DECIMAL_STR_WIDTH should probably add an extra "-" into account for negative
  numbers.

* Check that users of inotify's IN_DELETE_SELF flag are using it properly, as
  usually IN_ATTRIB is the right way to watch deleted files, as the former only
  fires when a file is actually removed from disk, i.e. the link count drops to
  zero and is not open anymore, while the latter happens when a file is
  unlinked from any dir.

* port systemctl, busctl, … over to format-table.[ch]'s table formatters

* pid1: lock image configured with RootDirectory=/RootImage= using the usual nspawn semantics while the unit is up

* add --vacuum-xyz options to coredumpctl, matching those journalctl already has.

* introduce Ephemeral= unit file switch, that creates an ephemeral copy of all
  files and directories that are left writable for a unit, and which are
  removed after the unit goes down again. A bit like --ephemeral for
  systemd-nspawn but for system services. If used together with RootImage= this
  should reflink the image file itself.

  Related: add Ephemeral=<path1> <path2> … which would allow marking
  specific paths only like this.

* add CopyFile= or so as unit file setting that may be used to copy files or
  directory trees from the host to the services RootImage= and RootDirectory=
  environment. Which we can use for /etc/machine-id and in particular
  /etc/resolv.conf. Should be smart and do something useful on read-only
  images, for example fall back to read-only bind mounting the file instead.

* show invocation ID in systemd-run output

* bypass SIGTERM state in unit files if KillSignal is SIGKILL

* add proper dbus APIs for the various sd_notify() commands, such as MAINPID=1
  and so on, which would mean we could report errors and such.

* introduce DefaultSlice= or so in system.conf that allows changing where we
  place our units by default, i.e. change system.slice to something
  else. Similar, ManagerSlice= should exist so that PID1's own scope unit could
  be moved somewhere else too. Finally machined and logind should get similar
  options so that it is possible to move user session scopes and machines to a
  different slice too by default. Usecase: people who want to put resources on
  the entire system, with the exception of one specific service. See:
  https://lists.freedesktop.org/archives/systemd-devel/2018-February/040369.html

* maybe rework get_user_creds() to query the user database if $SHELL is used
  for root, but only then.

* be stricter with fds we receive for the fdstore: close them asynchronously

* calenderspec: add support for week numbers and day numbers within a
  year. This would allow us to define "bi-weekly" triggers safely.

* sd-bus: add vtable flag, that may be used to request client creds implicitly
  and asynchronously before dispatching the operation

* sd-bus: parse addresses given in sd_bus_set_addresses immediately and not
  only when used. Add unit tests.

* make use of ethtool veth peer info in machined, for automatically finding out
  host-side interface pointing to the container.

* add some special mode to LogsDirectory=/StateDirectory=… that allows
  declaring these directories without necessarily pulling in deps for them, or
  creating them when starting up. That way, we could declare that
  systemd-journald writes to /var/log/journal, which could be useful when we
  doing disk usage calculations and so on.

* taint systemd if there are fewer than 65536 users assigned (userns) to the system.

* deprecate RootDirectoryStartOnly= in favour of a new ExecStart= prefix char

* add a new RuntimeDirectoryPreserve= mode that defines a similar lifecycle for
  the runtime dir as we maintain for the fdstore: i.e. keep it around as long
  as the unit is running or has a job queued.

* support projid-based quota in machinectl for containers

* add a way to lock down cgroup migration: a boolean, which when set for a unit
  makes sure the processes in it can never migrate out of it

* blog about fd store and restartable services

* document Environment=SYSTEMD_LOG_LEVEL=debug drop-in in debugging document

* rework ExecOutput and ExecInput enums so that EXEC_OUTPUT_NULL loses its
  magic meaning and is no longer upgraded to something else if set explicitly.

* in the long run: permit a system with /etc/machine-id linked to /dev/null, to
  make it lose its identity, i.e. be anonymous. For this we'd have to patch
  through the whole tree to make all code deal with the case where no machine
  ID is available.

* optionally, collect cgroup resource data, and store it in per-unit RRD files,
  suitable for processing with rrdtool. Add bus API to access this data, and
  possibly implement a CPULoad property based on it.

* beef up pam_systemd to take unit file settings such as cgroups properties as
  parameters

* maybe hook of xfs/ext4 quotactl() with services? i.e. automatically manage
  the quota of the user indicated in User= via unit file settings, like the
  other resource management concepts. Would mix nicely with DynamicUser=1. Or
  alternatively, do this with projids, so that we can also cover services
  running as root. Quota should probably cover all the special dirs such as
  StateDirectory=, LogsDirectory=, CacheDirectory=, as well as RootDirectory= if it
  is set, plus the whole disk space any image configured with RootImage=.

* In DynamicUser= mode: before selecting a UID, use disk quota APIs on relevant
  disks to see if the UID is already in use.

* expose IO accounting data on the bus, show it in systemd-run --wait and log
  about it in the resource log message

* Add AddUser= setting to unit files, similar to DynamicUser=1 which however
  creates a static, persistent user rather than a dynamic, transient user. We
  can leverage code from sysusers.d for this.

* add some optional flag to ReadWritePaths= and friends, that has the effect
  that we create the dir in question when the service is started. Example:

  ReadWritePaths=:/var/lib/foobar

* hostnamed: populate form factor data from a new hwdb database, so that old
  yogas can be recognized as "convertible" too, even if they predate the DMI
  "convertible" form factor

* Add ExecMonitor= setting. May be used multiple times. Forks off a process in
  the service cgroup, which is supposed to monitor the service, and when it
  exits the service is considered failed by its monitor.

* track the per-service PAM process properly (i.e. as an additional control
  process), so that it may be queried on the bus and everything.

* add a new "debug" job mode, that is propagated to unit_start() and for
  services results in two things: we raise SIGSTOP right before invoking
  execve() and turn off watchdog support. Then, use that to implement
  "systemd-gdb" for attaching to the start-up of any system service in its
  natural habitat.

* gpt-auto logic: support encrypted swap, add kernel cmdline option to force it, and honour a gpt bit about it, plus maybe a configuration file

* add a percentage syntax for TimeoutStopSec=, e.g. TimeoutStopSec=150%, and
  then use that for the setting used in user@.service. It should be understood
  relative to the configured default value.

* enable LockMLOCK to take a percentage value relative to physical memory

* Permit masking specific netlink APIs with RestrictAddressFamily=

* define gpt header bits to select volatility mode

* ProtectClock= (drops CAP_SYS_TIMES, adds seecomp filters for settimeofday, adjtimex), sets DeviceAllow o /dev/rtc

* ProtectTracing= (drops CAP_SYS_PTRACE, blocks ptrace syscall, makes /sys/kernel/tracing go away)

* ProtectMount= (drop mount/umount/pivot_root from seccomp, disallow fuse via DeviceAllow, imply Mountflags=slave)

* ProtectKeyRing= to take keyring calls away

* RemoveKeyRing= to remove all keyring entries of the specified user

* ProtectReboot= that masks reboot() and kexec_load() syscalls, prohibits kill
  on PID 1 with the relevant signals, and makes relevant files in /sys and
  /proc (such as the sysrq stuff) unavailable

* Support ReadWritePaths/ReadOnlyPaths/InaccessiblePaths in systemd --user instances
  via the new unprivileged Landlock LSM (https://landlock.io)

* make sure the ratelimit object can deal with USEC_INFINITY as way to turn off things

* in nss-systemd, if we run inside of RootDirectory= with PrivateUsers= set,
  find a way to map the User=/Group= of the service to the right name. This way
  a user/group for a service only has to exist on the host for the right
  mapping to work.

* add bus API for creating unit files in /etc, reusing the code for transient units

* add bus API to remove unit files from /etc

* add bus API to retrieve current unit file contents (i.e. implement "systemctl cat" on the bus only)

* rework fopen_temporary() to make use of open_tmpfile_linkable() (problem: the
  kernel doesn't support linkat() that replaces existing files, currently)

* transient units: don't bother with actually setting unit properties, we
  reload the unit file anyway

* optionally, also require WATCHDOG=1 notifications during service start-up and shutdown

* cache sd_event_now() result from before the first iteration...

* PID1: find a way how we can reload unit file configuration for
  specific units only, without reloading the whole of systemd

* add an explicit parser for LimitRTPRIO= that verifies
  the specified range and generates sane error messages for incorrect
  specifications.

* when we detect that there are waiting jobs but no running jobs, do something

* push CPUAffinity= also into the "cpuset" cgroup controller

* PID 1 should send out sd_notify("WATCHDOG=1") messages (for usage in the --user mode, and when run via nspawn)

* there's probably something wrong with having user mounts below /sys,
  as we have for debugfs. for example, src/core/mount.c handles mounts
  prefixed with /sys generally special.
  http://lists.freedesktop.org/archives/systemd-devel/2015-June/032962.html

* fstab-generator: default to tmpfs-as-root if only usr= is specified on the kernel cmdline

* initrd-parse-etc.service: can we skip daemon-reload if /sysroot/etc/fstab is missing?
  Note that we start initrd-fs.target and initrd-cleanup.target there, so a straightforward
  ConditionPathExists= is not enough.

* docs: bring http://www.freedesktop.org/wiki/Software/systemd/MyServiceCantGetRealtime up to date

* add a job mode that will fail if a transaction would mean stopping
  running units. Use this in timedated to manage the NTP service
  state.
  http://lists.freedesktop.org/archives/systemd-devel/2015-April/030229.html

* The udev blkid built-in should expose a property that reflects
  whether media was sensed in USB CF/SD card readers. This should then
  be used to control SYSTEMD_READY=1/0 so that USB card readers aren't
  picked up by systemd unless they contain a medium. This would mirror
  the behaviour we already have for CD drives.

* hostnamectl: show root image uuid

* Find a solution for SMACK capabilities stuff:
  http://lists.freedesktop.org/archives/systemd-devel/2014-December/026188.html

* synchronize console access with BSD locks:
  http://lists.freedesktop.org/archives/systemd-devel/2014-October/024582.html

* as soon as we have sender timestamps, revisit coalescing multiple parallel daemon reloads:
  http://lists.freedesktop.org/archives/systemd-devel/2014-December/025862.html

* figure out when we can use the coarse timers

* maybe allow timer units with an empty Units= setting, so that they
  can be used for resuming the system but nothing else.

* what to do about udev db binary stability for apps? (raw access is not an option)

* exponential backoff in timesyncd when we cannot reach a server

* timesyncd: add ugly bus calls to set NTP servers per-interface, for usage by NM

* merge ~/.local/share and ~/.local/lib into one similar /usr/lib and /usr/share....

* add systemd.abort_on_kill or some other such flag to send SIGABRT instead of SIGKILL
  (throughout the codebase, not only PID1)

* drop nss-myhostname in favour of nss-resolve?

* resolved:
  - mDNS/DNS-SD
        - service registration
        - service/domain/types browsing
        - avahi compat
  - DNS-SD service registration from socket units
  - resolved should optionally register additional per-interface LLMNR
    names, so that for the container case we can establish the same name
    (maybe "host") for referencing the server, everywhere.
  - allow clients to request DNSSEC for a single lookup even if DNSSEC is off (?)
  - hook up resolved with machined-based address resolution

* refcounting in sd-resolve is borked

* add new gpt type for btrfs volumes

* generator that automatically discovers btrfs subvolumes, identifies their purpose based on some xattr on them.

* a way for container managers to turn off getty starting via $container_headless= or so...

* figure out a nice way how we can let the admin know what child/sibling unit causes cgroup membership for a specific unit

* For timer units: add some mechanisms so that timer units that trigger immediately on boot do not have the services
  they run added to the initial transaction and thus confuse Type=idle.

* add bus api to query unit file's X fields.

* gpt-auto-generator:
  - Define new partition type for encrypted swap? Support probed LUKS for encrypted swap?
  - Make /home automount rather than mount?

* add generator that pulls in systemd-network from containers when
  CAP_NET_ADMIN is set, more than the loopback device is defined, even
  when it is otherwise off

* MessageQueueMessageSize= (and suchlike) should use parse_iec_size().

* implement Distribute= in socket units to allow running multiple
  service instances processing the listening socket, and open this up
  for ReusePort=

* cgroups:
  - implement per-slice CPUFairScheduling=1 switch
  - introduce high-level settings for RT budget, swappiness
  - how to reset dynamically changed unit cgroup attributes sanely?
  - when reloading configuration, apply new cgroup configuration
  - when recursively showing the cgroup hierarchy, optionally also show
    the hierarchies of child processes

* transient units:
  - add field to transient units that indicate whether systemd or somebody else saves/restores its settings, for integration with libvirt

* when we detect low battery and no AC on boot, show pretty splash and refuse boot

* libsystemd-journal, libsystemd-login, libudev: add calls to easily attach these objects to sd-event event loops

* be more careful what we export on the bus as (usec_t) 0 and (usec_t) -1

* rfkill,backlight: we probably should run the load tools inside of the udev rules so that the state is properly initialized by the time other software sees it

* After coming back from hibernation reset hibernation swap partition using the /dev/snapshot ioctl APIs

* If we try to find a unit via a dangling symlink, generate a clean
  error. Currently, we just ignore it and read the unit from the search
  path anyway.

* refuse boot if /usr/lib/os-release is missing or /etc/machine-id cannot be set up

* man: the documentation of Restart= currently is very misleading and suggests the tools from ExecStartPre= might get restarted.

* load .d/*.conf dropins for device units

* There's currently no way to cancel fsck (used to be possible via C-c or c on the console)

* add option to sockets to avoid activation. Instead just drop packets/connections, see http://cyberelk.net/tim/2012/02/15/portreserve-systemd-solution/

* make sure systemd-ask-password-wall does not shutdown systemd-ask-password-console too early

* verify that the AF_UNIX sockets of a service in the fs still exist
  when we start a service in order to avoid confusion when a user
  assumes starting a service is enough to make it accessible

* Make it possible to set the keymap independently from the font on
  the kernel cmdline. Right now setting one resets also the other.

* and a dbus call to generate target from current state

* investigate whether the gnome pty helper should be moved into systemd, to provide cgroup support.

* dot output for --test showing the 'initial transaction'

* be able to specify a forced restart of service A where service B depends on, in case B
  needs to be auto-respawned?

* pid1:
  - When logging about multiple units (stopping BoundTo units, conflicts, etc.),
    log both units as UNIT=, so that journalctl -u triggers on both.
  - generate better errors when people try to set transient properties
    that are not supported...
    http://lists.freedesktop.org/archives/systemd-devel/2015-February/028076.html
  - maybe introduce WantsMountsFor=? Usecase:
    http://lists.freedesktop.org/archives/systemd-devel/2015-January/027729.html
  - recreate systemd's D-Bus private socket file on SIGUSR2
  - move PAM code into its own binary
  - when we automatically restart a service, ensure we restart its rdeps, too.
  - hide PAM options in fragment parser when compile time disabled
  - Support --test based on current system state
  - If we show an error about a unit (such as not showing up) and it has no Description string, then show a description string generated form the reverse of unit_name_mangle().
  - after deserializing sockets in socket.c we should reapply sockopts and things
  - drop PID 1 reloading, only do reexecing (difficult: Reload()
    currently is properly synchronous, Reexec() is weird, because we
    cannot delay the response properly until we are back, so instead of
    being properly synchronous we just keep open the fd and close it
    when done. That means clients do not get a successful method reply,
    but much rather a disconnect on success.
  - when breaking cycles drop sysv services first, then services from /run, then from /etc, then from /usr
  - when a bus name of a service disappears from the bus make sure to queue further activation requests
  - maybe introduce CoreScheduling=yes/no to optionally set a PR_SCHED_CORE cookie, so that all
    processes in a service's cgroup share the same cookie and are guaranteed not to share SMT cores
    with other units https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/hw-vuln/core-scheduling.rst

* unit files:
  - allow port=0 in .socket units
  - maybe introduce ExecRestartPre=
  - add ReloadSignal= for configuring a reload signal to use
  - implement Register= switch in .socket units to enable registration
    in Avahi, RPC and other socket registration services.
  - allow Type=simple with PIDFile=
    https://bugzilla.redhat.com/show_bug.cgi?id=723942
  - allow writing multiple conditions in unit files on one line
  - introduce Type=pid-file
  - add a concept of RemainAfterExit= to scope units
  - Allow multiple ExecStart= for all Type= settings, so that we can cover rescue.service nicely
  - add verification of [Install] section to systemd-analyze verify

* timer units:
  - timer units should get the ability to trigger when:
    o DST changes
  - Modulate timer frequency based on battery state

* add libsystemd-password or so to query passwords during boot using the password agent logic

* clean up date formatting and parsing so that all absolute/relative timestamps we format can also be parsed

* on shutdown: move utmp, wall, audit logic all into PID 1 (or logind?), get rid of systemd-update-utmp-runlevel

* make repeated alt-ctrl-del presses printing a dump

* hostnamed: before returning information from /etc/machine-info.conf check the modification data and reread. Similar for localed, ...

* currently x-systemd.timeout is lost in the initrd, since crypttab is copied into dracut, but fstab is not

* add a pam module that passes the hdd passphrase into the PAM stack and then expires it, for usage by gdm auto-login.

* add a pam module that on password changes updates any LUKS slot where the password matches

* test/:
  - add unit tests for config_parse_device_allow()

* seems that when we follow symlinks to units we prefer the symlink
  destination path over /etc and /usr. We should not do that. Instead
  /etc should always override /run+/usr and also any symlink
  destination.

* when isolating, try to figure out a way how we implicitly can order
  all units we stop before the isolating unit...

* teach ConditionKernelCommandLine= globs or regexes (in order to match foobar={no,0,off})

* Add ConditionDirectoryNotEmpty= handle non-absoute paths as a search path or add
  ConditionConfigSearchPathNotEmpty= or different syntax? See the discussion starting at
  https://github.com/systemd/systemd/pull/15109#issuecomment-607740136.

* BootLoaderSpec: Clarify that the kernel has to be in $BOOT. Clarify
  that the boot loader should be installed to the ESP. Define a way
  how an installer can figure out whether a BLS compliant boot loader
  is installed.

* think about requeuing jobs when daemon-reload is issued? usecase:
  the initrd issues a reload after fstab from the host is accessible
  and we might want to requeue the mounts local-fs acquired through
  that automatically.

* systemd-inhibit: make taking delay locks useful: support sending SIGINT or SIGTERM on PrepareForSleep()

* remove any syslog support from log.c — we probably cannot do this before split-off udev is gone for good

* shutdown logging: store to EFI var, and store to USB stick?

* merge unit_kill_common() and unit_kill_context()

* hw watchdog: optionally try to use the preset watchdog timeout instead of always overriding it
  https://bugs.freedesktop.org/show_bug.cgi?id=54712

* add a dependency on standard-conf.xml and other included files to man pages

* MountFlags=shared acts as MountFlags=slave right now.

* properly handle loop back mounts via fstab, especially regards to fsck/passno

* initialize the hostname from the fs label of /, if /etc/hostname does not exist?

* sd-bus:
  - EBADSLT handling
  - GetAllProperties() on a non-existing object does not result in a failure currently
  - port to sd-resolve for connecting to TCP dbus servers
  - see if we can introduce a new sd_bus_get_owner_machine_id() call to retrieve the machine ID of the machine of the bus itself
  - see if we can drop more message validation on the sending side
  - add API to clone sd_bus_message objects
  - longer term: priority inheritance
  - dbus spec updates:
       - NameLost/NameAcquired obsolete
       - GVariant
       - path escaping
  - update systemd.special(7) to mention that dbus.socket is only about the compatibility socket now

* sd-event
  - allow multiple signal handlers per signal?
  - document chaining of signal handler for SIGCHLD and child handlers
  - define more intervals where we will shift wakeup intervals around in, 1h, 6h, 24h, ...
  - maybe support iouring as backend, so that we allow hooking read and write
    operations instead of IO ready events into event loops. See considerations
    here:
    http://blog.vmsplice.net/2020/07/rethinking-event-loop-integration-for.html

* dbus: when a unit failed to load (i.e. is in UNIT_ERROR state), we
  should be able to safely try another attempt when the bus call LoadUnit() is invoked.

* maybe do not install getty@tty1.service symlink in /etc but in /usr?

* print a nicer explanation if people use variable/specifier expansion in ExecStart= for the first word

* mount: turn dependency information from /proc/self/mountinfo into dependency information between systemd units.

* firstboot: allow provisioning of /etc/hosts entries, so that we can via the
  credentials logic insert host name to resolve into containers/hosts. Usecase:
  fork a container, and make it ping some specific address which is defined by
  the host on invocation

* systemd-firstboot: make sure to always use chase_symlinks() before
  reading/writing files

* firstboot: make it useful to be run immediately after yum --installroot to set up a machine. (most specifically, make --copy-root-password work even if /etc/passwd already exists

* sd-boot: define a drop-in dir in the ESP that may contain X.509
  certificates. If the firmware is detected to be in setup mode, automatically
  enroll them as PK/KEK/db, turn off setup mode and proceed. Optionally,
  instead of auto-enrolling them add them to the sd-boot menu, giving the user
  the option to manually enroll them, after selecting the menu entry. This way,
  installer images can just drop the certfiicates in the ESP, and on first boot
  can easily enroll the keys without ever booting up.

* efi stub: optionally, load initrd from disk as a separate file, HMAC check it
  with key from TPM, bound to PCR, refusing if failing. This would then allow
  traditional distros that generate initrds locally to secure them with TPM:
  after generating the initrd, do the HMAC calculation, put result in initrd
  filename, done. This would then bind the validity of the initrd to the local
  host, and used kernel, and means people cannot change initrd or kernel
  without booting the kernel + initrd.

* EFI:
  - honor language efi variables for default language selection (if there are any?)
  - honor timezone efi variables for default timezone selection (if there are any?)
  - change bootctl to be backed by systemd-bootd to control temporary and persistent default boot goal plus efi variables
* bootctl
  - recognize the case when not booted on EFI

* bootctl,sd-boot: actually honour the "architecture" key

* bootctl:
  - teach it to prepare an ESP wholesale, i.e. with mkfs.vfat invocation
  - teach it to copy in unified kernel images and maybe type #1 boot loader spec entries from host
  - make it operate on loopback files, dissecting enough to find ESP to operate on

* logind:
  - logind: optionally, ignore idle-hint logic for autosuspend, block suspend as long as a session is around
  - logind: wakelock/opportunistic suspend support
  - Add pretty name for seats in logind
  - logind: allow showing logout dialog from system?
  - add Suspend() bus calls which take timestamps to fix double suspend issues when somebody hits suspend and closes laptop quickly.
  - if pam_systemd is invoked by su from a process that is outside of a
    any session we should probably just become a NOP, since that's
    usually not a real user session but just some system code that just
    needs setuid().
  - logind: make the Suspend()/Hibernate() bus calls wait for the for
    the job to be completed. before returning, so that clients can wait
    for "systemctl suspend" to finish to know when the suspending is
    complete.
  - logind: when the power button is pressed short, just popup a
    logout dialog. If it is pressed for 1s, do the usual
    shutdown. Inspiration are Macs here.
  - expose "Locked" property on logind session objects
  - maybe allow configuration of the StopTimeout for session scopes
  - rename session scope so that it includes the UID. THat way
    the session scope can be arranged freely in slices and we don't have
    make assumptions about their slice anymore.
  - follow PropertiesChanged state more closely, to deal with quick logouts and
    relogins
  - (optionally?) spawn seat-manager@$SEAT.service whenever a seat shows up that as CanGraphical set

* move logind udev rules to top-level rule.d/ directory

* move multiseat vid/pid matches from logind udev rule to hwdb

* logind: rework pam_logind to also do a bus call in case of invocation from
  user@.service, which returns the XDG_RUNTIME_DIR value, and make this
  behaviour selectable via pam module option.

* delay activation of logind until somebody logs in, or when /dev/tty0 pulls it
  in or lingering is on (so that containers don't bother with it until PAM is used). also exit-on-idle

* journal:
  - consider introducing implicit _TTY= + _PPID= + _EUID= + _EGID= + _FSUID= + _FSGID= fields
  - journald: also get thread ID from client, plus thread name
  - journal: when waiting for journal additions in the client always sleep at least 1s or so, in order to minimize wakeups
  - add API to close/reopen/get fd for journal client fd in libsystemd-journal.
  - fall back to /dev/log based logging in libsystemd-journal, if we cannot log natively?
  - declare the local journal protocol stable in the wiki interface chart
  - sd-journal: speed up sd_journal_get_data() with transparent hash table in bg
  - journald: when dropping msgs due to ratelimit make sure to write
    "dropped %u messages" not only when we are about to print the next
    message that works, but already after a short timeout
  - check if we can make journalctl by default use --follow mode inside of less if called without args?
  - maybe add API to send pairs of iovecs via sd_journal_send
  - journal: add a setgid "systemd-journal" utility to invoke from libsystemd-journal, which passes fds via STDOUT and does PK access
  - journactl: support negative filtering, i.e. FOOBAR!="waldo",
    and !FOOBAR for events without FOOBAR.
  - journal: store timestamp of journal_file_set_offline() in the header,
    so it is possible to display when the file was last synced.
  - journal-send.c, log.c: when the log socket is clogged, and we drop, count this and write a message about this when it gets unclogged again.
  - journal: find a way to allow dropping history early, based on priority, other rules
  - journal: When used on NFS, check payload hashes
  - journald: add kernel cmdline option to disable ratelimiting for debug purposes
  - refuse taking lower-case variable names in sd_journal_send() and friends.
  - journald: we currently rotate only after MaxUse+MaxFilesize has been reached.
  - journal: deal nicely with byte-by-byte copied files, especially regards header
  - journal: sanely deal with entries which are larger than the individual file size, but where the components would fit
  - Replace utmp, wtmp, btmp, and lastlog completely with journal
  - journalctl: instead --after-cursor= maybe have a --cursor=XYZ+1 syntax?
  - when a kernel driver logs in a tight loop, we should ratelimit that too.
  - journald: optionally, log debug messages to /run but everything else to /var
  - journald: when we drop syslog messages because the syslog socket is
    full, make sure to write how many messages are lost as first thing
    to syslog when it works again.
  - journald: allow per-priority and per-service retention times when rotating/vacuuming
  - journald: make use of uid-range.h to managed uid ranges to split
    journals in.
  - journalctl: add the ability to look for the most recent process of a binary. journalctl /usr/bin/X11 --pid=-1 or so...
  - improve journalctl performance by loading journal files
    lazily. Encode just enough information in the file name, so that we
    do not have to open it to know that it is not interesting for us, for
    the most common operations.
  - man: document that corrupted journal files is nothing to act on
  - rework journald sigbus stuff to use mutex
  - Set RLIMIT_NPROC for systemd-journal-xyz, and all other of our
    services that run under their own user ids, and use User= (but only
    in a world where userns is ubiquitous since otherwise we cannot
    invoke those daemons on the host AND in a container anymore). Also,
    if LimitNPROC= is used without User= we should warn and refuse
    operation.
  - journalctl --verify: don't show files that are currently being
    written to as FAIL, but instead show that their are being written to.
  - add journalctl -H that talks via ssh to a remote peer and passes through
    binary logs data
  - add a version of --merge which also merges /var/log/journal/remote
  - journalctl: -m should access container journals directly by enumerating
    them via machined, and also watch containers coming and going.
    Benefit: nspawn --ephemeral would start working nicely with the journal.
  - assign MESSAGE_ID to log messages about failed services
  - check if loop in decompress_blob_xz() is necessary

* journald: support RFC3164 fully for the incoming syslog transport, see
  https://github.com/systemd/systemd/issues/19251#issuecomment-816601955

* Hook up journald's FSS logic with TPM2: seal the verification disk by
  time-based policy, so that the verification key can remain on host and ve
  validated via TPM.

* build short web pages out of each catalog entry, build them along with man
  pages, and include hyperlinks to them in the journal output

* journald: do journal file writing out-of-process, with one writer process per
  client UID, so that synthetic hash table collisions can slow down a specific
  user's journal stream down but not the others.

* tweak journald context caching. In addition to caching per-process attributes
  keyed by PID, cache per-cgroup attributes (i.e. the various xattrs we read)
  keyed by cgroup path, and guarded by ctime changes. This should provide us
  with a nice speed-up on services that have many processes running in the same
  cgroup.

* maybe add call sd_journal_set_block_timeout() or so to set SO_SNDTIMEO for
  the sd-journal logging socket, and, if the timeout is set to 0, sets
  O_NONBLOCK on it. That way people can control if and when to block for
  logging.

* journalctl: make sure -f ends when the container indicated by -M terminates

* journald: sigbus API via a signal-handler safe function that people may call
  from the SIGBUS handler

* add a test if all entries in the catalog are properly formatted.
    (Adding dashes in a catalog entry currently results in the catalog entry
     being silently skipped. journalctl --update-catalog must warn about this,
     and we should also have a unit test to check that all our message are OK.)

* homed:
  - when user tries to log into record signed by unrecognized key, automatically add key to our chain after polkit auth
  - rollback when resize fails mid-operation
  - GNOME's side for forget key on suspend (requires rework so that lock screen runs outside of uid)
  - resize on login?
  - shrink fs on logout?
  - update LUKS password on login if we find there's a password that unlocks the JSON record but not the LUKS device.
  - create on activate?
  - properties: icon url?, preferred session type?, administrator bool (which translates to 'wheel' membership)?, address?, telephone?, vcard?, samba stuff?, parental controls?
  - communicate clearly when usb stick is safe to remove. probably involves
    beefing up logind to make pam session close hook synchronous and wait until
    systemd --user is shut down.
  - logind: maybe keep a "busy fd" as long as there's a non-released session around or the user@.service
  - maybe make automatic, read-only, time-based reflink-copies of LUKS disk
    images (and btrfs snapshots of subvolumes) (think: time machine)
  - distinguish destroy / remove (i.e. currently we can unregister a user, unregister+remove their home directory, but not just remove their home directory)
  - in systemd's PAMName= logic: query passwords with ssh-askpassword, so that we can make "loginctl set-linger" mode work
  - fingerprint authentication, pattern authentication, …
  - make sure "classic" user records can also be managed by homed
  - make size of $XDG_RUNTIME_DIR configurable in user record
  - query password from kernel keyring first
  - update even if record is "absent"
  - add a "access mode" + "fstype" field to the "status" section of json identity records reflecting the actually used access mode and fstype, even on non-luks backends
  - move acct mgmt stuff from pam_systemd_home to pam_systemd?
  - when "homectl --pkcs11-token-uri=" is used, synthesize ssh-authorized-keys records for all keys we have private keys on the stick for
  - make slice for users configurable (requires logind rework)
  - logind: populate auto-login list bus property from PKCS#11 token
  - when determining state of a LUKS home directory, check DM suspended sysfs file
  - introduce API for "making room", that grows/shrinks home directory
    according to elastic parameters, discards blocks, and removes additional snapshots. Call it
    either from UI when disk space gets low
  - when homed is in use, maybe start the user session manager in a mount namespace with MS_SLAVE,
    so that mounts propagate down but not up - eg, user A setting up a backup volume
    doesn't mean user B sees it

* homed: during login resize fs automatically towards size goal. Specifically,
  resize to diskSize if possible, but leave a certain amount (configured by a
  new value diskLeaveFreeSize) of space free on the backing fs.

* homed: permit multiple user record signing keys to be used locally, and pick
  the right one for signing records automatically depending on a pre-existing
  signature

* homed: add a way to "adopt" a home directory, i.e. strip foreign signatures
  and insert a local signature instead.

* homed: as an extension to the directory+subvolume backend: if located on
  especially marked fs, then sync down password into LUKS header of that fs,
  and always verify passwords against it too. Bootstrapping is a problem
  though: if no one is logged in (or no other user even exists yet), how do you
  unlock the volume in order to create the first user and add the first pw.

* homed: support new FS_IOC_ADD_ENCRYPTION_KEY ioctl for setting up fscrypt

* homed: maybe pre-create ~/.cache as subvol so that it can have separate quota
  easily?

* homed: if kernel 5.12 uid mapping mounts exist, use that instead of recursive
  chowns.

* add a switch to homectl (maybe called --first-boot) where it will check if
  any non-system users exist, and if not prompts interactively for basic user
  info, mimicking systemd-firstboot. Then, place this in a service that runs
  after systemd-homed, but before gdm and friends, as a simple, barebones
  fallback logic to get a regular user created on uninitialized systems.

* homed: store PKCS#11 + FIDO2 token info in LUKS2 header, compatible with
  systemd-cryptsetup, so that it can unlock homed volumes

* homed: try to unmount in regular intervals when home dir was busy when we
  tried because idle.

* homed: keep an fd to the homedir open at all times, to keep the fs pinned
  (autofs and such) while user is logged in.

* when we resize disks (homed?) always round up to 4K sectors, not 512K

* add a new switch --auto-definitions=yes/no or so to systemd-repart. If
  specified, synthesize a definition automatically if we can: enlarge last
  partition on disk, but only if it is marked for growing and not read-only.

* systemd-repart: read LUKS encryption key from $CREDENTIALS_PATH

* systemd-repart: add a switch to factory reset the partition table without
  immediately applying the new configuration again. i.e. --factory-reset=leave
  or so. (this is useful to factory reset an image, then putting it into
  another machine, ensuring that luks key is generated on new machine, not old)

* systemd-repart: support setting up dm-integrity with HMAC

* systemd-repart: maybe remove half-initialized image on failure. It fails
  if the output file exists, so a repeated invocation will usually fail if
  something goes wrong on the way.

* systemd-repart: drop pager mode on normal operation?

* systemd-repart: by default generate minimized partition tables (i.e. tables
  that only cover the space actually used, excluding any free space at the
  end), in order to maximize dd'ability. Requires libfdisk work, see
  https://github.com/karelzak/util-linux/issues/907

* systemd-repart: MBR partition table support. Care needs to be taken regarding
  Type=, so that partition definitions can sanely apply to both the GPT and the
  MBR case. Idea: accept syntax "Type=gpt:home mbr:0x83" for setting the types
  for the two partition types explicitly. And provide an internal mapping so
  that "Type=linux-generic" maps to the right types for both partition tables
  automatically.

* systemd-repart: allow sizing partitions as factor of available RAM, so that
  we can reasonably size swap partitions for hibernation.

* systemd-repart: allow boolean option that ensures that if existing partition
  doesn't exist within the configured size bounds the whole command fails. This
  is useful to implement ESP vs. XBOOTLDR schemes in installers: have one set
  of repart files for the case where ESP is large enough and one where it isn't
  and XBOOTLDR is added in instead.  Then apply the former first, and if it
  fails to apply use the latter.

* systemd-repart: add per-partition option to never reuse existing partition
  and always create anew even if matching partition already exists.

* systemd-repart: add per-partition option to fail if partition already exist,
  i.e. is not added new. Similar, add option to fail if partition does not exist yet.

* systemd-repart: allow disabling growing of specific partitions, or making
  them (think ESP: we don't ever want to grow it, since we cannot resize vfat)

* systemd-repart: make it a static checker during early boot for existence and
  absence of other partitions for trusted boot environments

* document:
  - document that deps in [Unit] sections ignore Alias= fields in
    [Install] units of other units, unless those units are disabled
  - man: clarify that time-sync.target is not only sysv compat but also useful otherwise. Same for similar targets
  - document that service reload may be implemented as service reexec
  - add a man page containing packaging guidelines and recommending usage of things like Documentation=, PrivateTmp=, PrivateNetwork= and ReadOnlyDirectories=/etc /usr.
  - document systemd-journal-flush.service properly
  - documentation: recommend to connect the timer units of a service to the service via Also= in [Install]
  - man: document the very specific env the shutdown drop-in tools live in
  - man: add more examples to man pages,
  -      in particular an example how to do the equivalent of switching runlevels
  - man: maybe sort directives in man pages, and take sections from --help and apply them to man too
  - document root=gpt-auto properly

* systemctl:
  - add systemctl switch to dump transaction without executing it
  - Add a verbose mode to "systemctl start" and friends that explains what is being done or not done
  - "systemctl disable" on a static unit prints no message and does
    nothing. "systemctl enable" does nothing, and gives a bad message
    about it. Should fix both to print nice actionable messages.
  - print nice message from systemctl --failed if there are no entries shown, and hook that into ExecStartPre of rescue.service/emergency.service
  - add new command to systemctl: "systemctl system-reexec" which reexecs as many daemons as virtually possible
  - systemctl enable: fail if target to alias into does not exist? maybe show how many units are enabled afterwards?
  - systemctl: "Journal has been rotated since unit was started." message is misleading
  - systemctl status output should include list of triggering units and their status

* introduce an option (or replacement) for "systemctl show" that outputs all
  properties as JSON, similar to busctl's new JSON output. In contrast to that
  it should skip the variant type string though.

* add an explicit "vertical" mode to format-table, so that "systemctl
  status"-like outputs (i.e. with a series of field names left and values
  right) become genuine first class citizens, and we gain automatic, sane JSON
  output for them.

* Add a "systemctl list-units --by-slice" mode or so, which rearranges the
  output of "systemctl list-units" slightly by showing the tree structure of
  the slices, and the units attached to them.

* add "systemctl wait" or so, which does what "systemd-run --wait" does, but
  for all units. It should be both a way to pin units into memory as well as a
  wait to retrieve their exit data.

* show whether a service has out-of-date configuration in "systemctl status" by
  using mtime data of ConfigurationDirectory=.

* "systemctl preset-all" should probably order the unit files it
  operates on lexicographically before starting to work, in order to
  ensure deterministic behaviour if two unit files conflict (like DMs
  do, for example)

* add "systemctl start -v foobar.service" that shows logs of a service
  while the start command runs. This is non-trivial to do without
  races though, since we should flush out all journal messages before
  returning from the "systemctl stop".

* systemctl: if some operation fails, show log output?

* Add a new verb "systemctl top"

* unit install:
  - "systemctl mask" should find all names by which a unit is accessible
    (i.e. by scanning for symlinks to it) and link them all to /dev/null

* nspawn:
  - emulate /dev/kmsg using CUSE and turn off the syslog syscall
    with seccomp. That should provide us with a useful log buffer that
    systemd can log to during early boot, and disconnect container logs
    from the kernel's logs.
  - as soon as networkd has a bus interface, hook up --network-interface=,
    --network-bridge= with networkd, to trigger netdev creation should an
    interface be missing
  - a nice way to boot up without machine id set, so that it is set at boot
    automatically for supporting --ephemeral. Maybe hash the host machine id
    together with the machine name to generate the machine id for the container
  - fix logic always print a final newline on output.
    https://github.com/systemd/systemd/pull/272#issuecomment-113153176
  - should optionally support receiving WATCHDOG=1 messages from its payload
    PID 1...
  - optionally automatically add FORWARD rules to iptables whenever nspawn is
    running, remove them when shut down.

* nspawn: make --bind= work sanely with --private-users when uid mapping mounts
  are used.

* nspawn: add support for sysext extensions, too. i.e. a new --extension=
  switch that takes one or more arguments, and applies the extensions already
  during startup.

* when main nspawn supervisor process gets suspended due to SIGSTOP/SIGTTOU or
  so, freeze the payload too.

* machined: add API to acquire UID range. add API to mount/dissect loopback
  file. Both protected by PK. Then make nspawn use these APIs to run
  unprivileged containers. i.e. push the truly privileged bits into machined,
  so that the client side can remain entirely unprivileged, with SUID or
  anything like that.

* nspawn: support time namespaces

* nspawn: on cgroupsv1 issue cgroup empty handler process based on host events,
  so that we make cgroup agent logic safe

* nspawn/machined: add API to invoke binary in container, then use that as
  fallback in "machinectl shell"

* nspawn: make nspawn suitable for shell pipelines: instead of triggering a
  hangup when input is finished, send ^D, which synthesizes an EOF. Then wait
  for hangup or ^D before passing on the EOF.

* nspawn: greater control over selinux label?

* nspawn: support that /proc, /sys/, /dev are pre-mounted

* machined:
  - add an API so that libvirt-lxc can inform us about network interfaces being
    removed or added to an existing machine
  - "machinectl migrate" or similar to copy a container from or to a
    difference host, via ssh
  - introduce systemd-nspawn-ephemeral@.service, and hook it into
    "machinectl start" with a new --ephemeral switch
  - "machinectl status" should also show internal logs of the container in
    question
  - "machinectl history"
  - "machinectl diff"
  - "machinectl commit" that takes a writable snapshot of a tree, invokes a
    shell in it, and marks it read-only after use

* udev:
  - move to LGPL
  - kill scsi_id
  - add trigger --subsystem-match=usb/usb_device device
  - reimport udev db after MOVE events for devices without dev_t

* coredump:
  - save coredump in Windows/Mozilla minidump format
  - when truncating coredumps, also log the full size that the process had, and make a metadata field so we can report truncated coredumps

* support crash reporting operation modes (https://live.gnome.org/GnomeOS/Design/Whiteboards/ProblemReporting)

* tmpfiles:
  - apply "x" on "D" too (see patch from William Douglas)
  - instead of ignoring unknown fields, reject them.
  - creating new directories/subvolumes/fifos/device nodes
    should not follow symlinks. None of the other adjustment or creation
    calls follow symlinks.
  - add --test mode
  - teach tmpfiles.d q/Q logic something sensible in the context of XFS/ext4
    project quota

* udev-link-config:
   - Make sure ID_PATH is always exported and complete for
     network devices where possible, so we can safely rely
     on Path= matching

* sd-rtnl:
   - add support for more attribute types
   - inbuilt piping support (essentially degenerate async)? see loopback-setup.c and other places

* networkd:
   - add more keys to [Route] and [Address] sections
   - add support for more DHCPv4 options (and, longer term, other kinds of dynamic config)
   - add reduced [Link] support to .network files
   - properly handle routerless dhcp leases
   - work with non-Ethernet devices
   - dhcp: do we allow configuring dhcp routes on interfaces that are not the one we got the dhcp info from?
   - the DHCP lease data (such as NTP/DNS) is still made available when
     a carrier is lost on a link. It should be removed instantly.
   - expose in the API the following bits:
         - option 15, domain name
         - option 12, hostname and/or option 81, fqdn
         - option 123, 144, geolocation
         - option 252, configure http proxy (PAC/wpad)
   - provide a way to define a per-network interface default metric value
     for all routes to it. possibly a second default for DHCP routes.
   - allow Name= to be specified repeatedly in the [Match] section. Maybe also
     support Name=foo*|bar*|baz ?
   - whenever uplink info changes, make DHCP server send out FORCERENEW

* in networkd, when matching device types, fix up DEVTYPE rubbish the kernel passes to us

* Figure out how to do unittests of networkd's state serialization

* dhcp:
   - figure out how much we can increase Maximum Message Size

* dhcp6:
   - add functions to set previously stored IPv6 addresses on startup and get
     them at shutdown; store them in client->ia_na
   - write more test cases
   - implement reconfigure support, see 5.3., 15.11. and 22.20.
   - implement support for temporary adressess (IA_TA)
   - implement dhcpv6 authentication
   - investigate the usefulness of Confirm messages; i.e. are there any
     situations where the link changes without any loss in carrier detection
     or interface down
   - some servers don't do rapid commit without a filled in IA_NA, verify
     this behavior
   - RouteTable= ?