From: Lennart Poettering Date: Tue, 17 Dec 2019 12:47:21 +0000 (+0100) Subject: man: document systemd-repart X-Git-Tag: v245-rc1~85^2~2 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=917cc8082bbd1d380ddf7cdc8ae40606a7de0bfd;p=thirdparty%2Fsystemd.git man: document systemd-repart --- diff --git a/man/repart.d.xml b/man/repart.d.xml new file mode 100644 index 00000000000..2fe74193d30 --- /dev/null +++ b/man/repart.d.xml @@ -0,0 +1,388 @@ + + + + + + repart.d + systemd + + + + repart.d + 5 + + + + repart.d + Partition Definition Files for Automatic Boot-Time Repartitioning + + + + /etc/repart.d/*.conf +/run/repart.d/*.conf +/usr/lib/repart.d/*.conf + + + + + Description + + repart.d/*.conf files describe basic properties of partitions of block + devices of the local system. They may be used to declare types, names and sizes of partitions that shall + exist. The + systemd-repart8 + service reads these files and attempts to add new partitions currently missing and enlarge existing + partitions according to these definitions. Operation is generally incremental, i.e. when applied, what + exists already is left intact, and partitions are never shrunk, moved or deleted. + + These definition files are useful for implementing operating system images that are prepared and + delivered with minimally sized images (for example lacking any state or swap partitions), and which on + first boot automatically take possession of any remaining disk space following a few basic rules. + + Currently, support for partition definition files is only implemented for GPT partitition + tables. + + Partition files are generally matched against any partitions already existing on disk in a simple + algorithm: the partition files are sorted by their filename (ignoring the directory prefix), and then + compared in order against existing partitions matching the same partition type UUID. Specifically, the + first existing partition with a specific partition type UUID is assigned the first definition file with + the same partition type UUID, and the second existing partition with a specific type UUID the second + partition file with the same type UUID, and so on. Any left-over partition files that have no matching + existing partition are assumed to define new partition that shall be created. Such partitions are + appended to the end of the partition table, in the order defined by their names utilizing the first + partition slot greater than the highest slot number currently in use. Any existing partitions that have + no matching partition file are left as they are. + + Note that these partition definition files do not describe the contents of the partitions, such as + the file system used. Separate mechanisms, such as + systemd-growfs8 and + systemd-makefs maybe be used to initialize or grow the file systems inside of these + partitions. + + + + [Partition] Section Options + + + + Type= + + The GPT partition type UUID to match. This may be a GPT partition type UUID such as + 4f68bce3-e8cd-4db1-96e7-fbcaf984b709, or one of the following special + identifiers: + + + GPT partition type identifiers + + + + + + + + Identifier + Explanation + + + + + + esp + EFI System Partition + + + + xbootldr + Extended Boot Loader Partition + + + + swap + Swap partition + + + + home + Home (/home/) partition + + + + srv + Server data (/srv/) partition + + + + var + Variable data (/var/) partition + + + + tmp + Temporary data (/var/tmp/) partition + + + + linux-generic + Generic Linux file system partition + + + + root + Root file system partition type appropriate for the local architecture (an alias for an architecture root file system partition type listed below, e.g. root-x86-64) + + + + root-verity + Verity data for the root file system partition for the local architecture + + + + root-secondary + Root file system partition of the secondary architecture of the local architecture; usually the matching 32bit architecture for the local 64bit architecture) + + + + root-secondary-verity + Verity data for the root file system partition of the secondary architecture + + + + root-x86 + Root file system partition for the x86 (32bit, aka i386) architecture + + + + root-x86-verity + Verity data for the x86 (32bit) root file system partition + + + + root-x86-64 + Root file system partition for the x86_64 (64bit, aka amd64) architecture + + + + root-x86-64-verity + Verity data for the x86_64 (64bit) root file system partition + + + + root-arm + Root file system partition for the ARM (32bit) architecture + + + + root-arm-verity + Verity data for the ARM (32bit) root file system partition + + + + root-arm64 + Root file system partition for the ARM (64bit, aka aarch64) architecture + + + + root-arm64-verity + Verity data for the ARM (64bit, aka aarch64) root file system partition + + + + root-ia64 + Root file system partition for the ia64 architecture + + + + root-ia64-verity + Verity data for the ia64 root file system partition + + + +
+ + This setting defaults to linux-generic. + + Most of the partition type UUIDs listed above are defined in the Discoverable Partitions + Specification. + + + + Label= + + The textual label to assign to the partition if none is assigned yet. Note that this + setting is not used for matching. It is also not used when a label is already set for an existing + partition. It is thus only used when a partition is newly created or when an existing one had a no + label set (that is: an empty label). If not specified a label derived from the partition type is + automatically used. + + + + Priority= + + A numeric priority to assign to this partition, in the range -2147483648…2147483647, + with smaller values indicating higher priority, and higher values indicating smaller priority. This + priority is used in case the configured size constraints on the defined partitions do not permit + fitting all partitions onto the available disk space. If the partitions do not fit, the highest + numeric partition priority of all defined partitions is determined, and all defined partitions with + this priority are removed from the list of new partitions to create (which may be multiple, if the + same priority is used for multiple partitions). The fitting algorithm is then tried again. If the + partitions still do not fit, the now highest numeric partition priority is determined, and the + matching partitions removed too, and so on. Partitions of a priority of 0 or lower are never + removed. If all partitions with a priority above 0 are removed and the partitions still do not fit on + the device the operation fails. Note that this priority has no effect on ordering partitions, for + that use the alphabetical order of the filenames of the partition definition files. Defaults to + 0. + + + + Weight= + + A numeric weight to assign to this partition in the range 0…1000000. Available disk + space is assigned the defined partitions according to their relative weights (subject to the size + constraints configured with SizeMinBytes=, SizeMaxBytes=), so + that a partition with weight 2000 gets double the space as one with weight 1000, and a partition with + weight 333 a third of that. Defaults to 1000. + + The Weight= setting is used to distribute available disk space in an + "elastic" fashion, based on the disk size and existing partitions. If a partition shall have a fixed + size use both SizeMinBytes= and SizeMaxBytes= with the same + value in order to fixate the size to one value, in which case the weight has no + effect. + + + + PaddingWeight= + + Similar to Weight= but sets a weight for the free space after the + partition (the "padding"). When distributing available space the weights of all partitions and all + defined padding is summed, and then each partition and padding gets the fraction defined by its + weight. Defaults to 0, i.e. by default no padding is applied. + + Padding is useful if empty space shall be left for later additions or a safety margin at the + end of the device or between partitions. + + + + SizeMinBytes= + SizeMaxBytes= + + Specifies minimum and maximum size constraints in bytes. Takes the usual K, M, G, T, + … suffixes (to the base of 1024). If SizeMinBytes= is specified the partition is + created at or grown to at least the specified size. If SizeMaxBytes= is specified + the partition is created at or grown to at most the specified size. The precise size is determined + through the weight value value configured with Weight=, see above. When + SizeMinBytes= is set equal to SizeMaxBytes= the configured + weight has no effect as the partition is explicitly sized to the specified fixed value. Note that + partitions are never created smaller than 4096 bytes, and since partitions are never shrunk the + previous size of the partition (in case the partition already exists) is also enforced as lower bound + for the new size. The values should be specified as multiples of 4096 bytes, and are rounded upwards + (in case of SizeMinBytes=) or downwards (in case of + SizeMaxBytes=) otherwise. If the backing device does not provide enough space to + fulfill the constraints placing the partition will fail. For partitions that shall be created, + depending on the setting of Priority= (see above) the partition might be dropped + and the placing algorithm restarted. By default no size constraints are set. + + + + PaddingMinBytes= + PaddingMaxBytes= + + Specifies minimum and maximum size constrains in bytes for the free space after the + partition (the "padding"). Semantics are similar to SizeMinBytes= and + SizeMaxBytes=, except that unlike partition sizes free space can be shrunk and can + be as small as zero. By default no size constraints on padding are set, so that only + PaddingWeight= determines the size of the padding applied. + + + + FactoryReset= + + Takes a boolean argument. If specified the partition is marked for removal during a + factory reset operation. This functionality is useful to implement schemes where images can be reset + into their original state by removing partitions and creating them anew. Defaults to off. + + + + + + Examples + + + Grow the root partition to the full disk size at first boot + + With the following file the root partition is automatically grown to the full disk if possible during boot. + + # /usr/lib/repart.d/50-root.conf +[Partition] +Type=root + + + + + Create a swap and home partition automatically on boot, if missing + + The home partition gets all available disk space while the swap partition gets 1G at most and 64M + at least. We set a priority > 0 on the swap partition to ensure the swap partition is not used if not + enough space is available. For every three bytes assigned to the home partition the swap partition gets + assigned one. + + # /usr/lib/repart.d/60-home.conf +[Partition] +Type=home + + + # /usr/lib/repart.d/70-swap.conf +[Partition] +Type=swap +SizeMinBytes=64M +SizeMaxBytes=1G +Priority=1 +Weight=333 + + + + + Create B partitions in an A/B Verity setup, if missing + + Let's say the vendor intends to update OS images in an A/B setup, i.e. with two root partitions + (and two matching Verity partitions) that shall be used alternatingly during upgrades. To minimize + image sizes the original image is shipped only with one root and one Verity partition (the "A" set), + and the second root and Verity partitions (the "B" set) shall be created on first boot on the free + space on the medium. + + # /usr/lib/repart.d/50-root.conf +[Partition] +Type=root +SizeMinBytes=512M +SizeMaxBytes=512M + + + # /usr/lib/repart.d/60-root-verity.conf +[Partition] +Type=root-verity +SizeMinBytes=64M +SizeMaxBytes=64M + + + The definitions above cover the "A" set of root partition (of a fixed 512M size) and Verity + partition for the root partition (of a fixed 64M size). Let's use symlinks to create the "B" set of + partitions, since after all they shall have the same properties and sizes as the "A" set. + +# ln -s 50-root.conf /usr/lib/repart.d/70-root-b.conf +# ln -s 60-root-verity.conf /usr/lib/repart.d/80-root-verity-b.conf + + + + + + + See Also + + systemd1, + systemd-repart8, + sfdisk8 + + + + diff --git a/man/rules/meson.build b/man/rules/meson.build index 90376da7759..3dc0a045a75 100644 --- a/man/rules/meson.build +++ b/man/rules/meson.build @@ -47,6 +47,7 @@ manpages = [ ['pam_systemd', '8', [], 'HAVE_PAM'], ['portablectl', '1', [], 'ENABLE_PORTABLED'], ['pstore.conf', '5', ['pstore.conf.d'], 'ENABLE_PSTORE'], + ['repart.d', '5', [], ''], ['resolvectl', '1', ['resolvconf'], 'ENABLE_RESOLVE'], ['resolved.conf', '5', ['resolved.conf.d'], 'ENABLE_RESOLVE'], ['runlevel', '8', [], ''], @@ -769,6 +770,7 @@ manpages = [ 'ENABLE_RANDOMSEED'], ['systemd-rc-local-generator', '8', [], ''], ['systemd-remount-fs.service', '8', ['systemd-remount-fs'], ''], + ['systemd-repart', '8', ['systemd-repart.service'], ''], ['systemd-resolved.service', '8', ['systemd-resolved'], 'ENABLE_RESOLVE'], ['systemd-rfkill.service', '8', diff --git a/man/systemd-makefs@.service.xml b/man/systemd-makefs@.service.xml index 8514af67bc4..d07d90315a4 100644 --- a/man/systemd-makefs@.service.xml +++ b/man/systemd-makefs@.service.xml @@ -80,6 +80,7 @@ systemd1, systemd.mount8, systemd-fstab-generator8, + systemd-repart8, mkfs.btrfs8, mkfs.cramfs8, mkfs.ext48, diff --git a/man/systemd-repart.xml b/man/systemd-repart.xml new file mode 100644 index 00000000000..cffcb5403ad --- /dev/null +++ b/man/systemd-repart.xml @@ -0,0 +1,269 @@ + + + + + + + + systemd-repart + systemd + + + + systemd-repart + 8 + + + + systemd-repart + systemd-repart.service + Automatically grow and add partitions + + + + + systemd-repart + OPTIONS + BLOCKDEVICE + + + systemd-repart.service + + + + Description + + systemd-repart grows and adds partitions to a partition table, based on the + configuration files described in + repart.d5. + + + If invoked with no arguments, it operates on the block device backing the root file system partition + of the OS, thus growing and adding partitions of the booted OS image itself. When called in the initial + RAM disk it operates on the block device backing /sysroot/ instead, i.e. on the + block device the system will soon transition into. The systemd-repart.service + service is generally run at boot in the initial RAM disk, in order to augment the partition table of the + OS before its partitions are mounted. systemd-repart (mostly) operates in a purely + incremental mode: it only grows existing and adds new partitions; it does not shrink, delete or move + existing partitions. The service is intended to be run on every boot, but when it detects that the + partition table already matches the installed repart.d/*.conf configuration + files, it executes no operation. + + systemd-repart is intended to be used when deploying OS images, to automatically + adjust them to the system they are running on, during first boot. This way the deployed image can be + minimal in size and may be augmented automatically at boot when needed, taking possession of disk space + available but not yet used. Specifically the following use cases are among those covered: + + + The root partition may be grown to cover the whole available disk space + A /home/, swap or /srv partition can be added in + A second (or third, …) root partition may be added in, to cover A/B style setups + where a second version of the root file system is alternatingly used for implementing update + schemes. The deployed image would carry only a single partition ("A") but on first boot a second + partition ("B") for this purpose is automatically created. + + + The algorithm executed by systemd-repart is roughly as follows: + + + The repart.d/*.conf configuration files are loaded and parsed, + and ordered by filename (without the directory suffix). + + The partition table already existing on the block device is loaded and + parsed. + + The existing partitions in the partition table are matched up with the + repart.d/*.conf files by GPT partition type UUID. The first existing partition + of a specific type is assigned the first configuration file declaring the same type. The second + existing partition of a specific type is then assigned the second configuration file declaring the same + type, and so on. After this iterative assigning is complete any left-over existing partitions that have + no matching configuration file are considered "foreign" and left as they are. And any configuration + files for which no partition currently exists are understood as a request to create such a + partition. + + Taking the size constraints and weights declared in the configuration files into + account, all partitions that shall be created are now allocated to the disk, taking up all free space, + always respecting the size and padding requests. Similar, existing partitions that are determined to + grow are grown. New partitions are always appended to the end of the existing partition table, taking + the first partition table slot whose index is greater than the indexes of all existing + partitions. Partition table slots are never reordered and thus partition numbers are ensured to remain + stable. Note that this allocation happens in RAM only, the partition table on disk is not updated + yet. + + All existing partitions for which configuration files exist and which currently have no + GPT partition label set will be assigned a label, either explicitly configured in the configuration or + (if that's missing) derived automatically from the partition type. The same is done for all partitions + that are newly created. These assignments are done in RAM only, too, the disk is not updated + yet. + + Similarly, all existing partitions for which configuration files exist and which + currently have an all-zero identifying UUID will be assigned a new UUID. This UUID is cryptographically + hashed from a common seed value together with the partition type UUID (and a counter in case multiple + partitions of the same type are defined), see below. The same is done for all partitions that are + created anew. These assignments are done in RAM only, too, the disk is not updated + yet. + + Similarly, if the disk's volume UUID is all zeroes it is also initialized, also + cryptographically hashed from the same common seed value. Also, in RAM only, too. + + The disk space assigned to new partitions (i.e. what was previously considered free + space but is no longer) is now erased. Specifically, all file system signatures are removed, and if the + device supports it the BLKDISCARD I/O control command is issued to inform the + hardware that the space is empty now. In addition any "padding" between partitions and at the end of + the device is similarly erased. + + The new partition table is finally written to disk. The kernel is asked to reread the + partition table. + + + As exception to the normally strictly incremental operation, when called in a special "factory + reset" mode systemd-repart may also be used to erase select existing partitions to + reset an installation back to vendor defaults. This mode of operation is used when either the + switch is passed on the tool's command line, or the + option specified on the kernel command line, or the + FactoryReset EFI variable (vendor UUID + 8cf2644b-4b0b-428f-9387-6d876050dc67) is set to "yes". It alters the algorithm above + slightly: between the 3rd and the 4th step above the any partition marked explicitly via the + FactoryReset= boolean is deleted, and the algorithm restarted, thus immediately + re-creating these partitions anew empty. + + Note that systemd-repart only changes partition tables, it does not create or + resize any file systems within these partitions. A separate mechanism should be used for that, for + example + systemd-growfs8 and + systemd-makefs. + + The UUIDs identifying the new partitions created (or assigned to existing partitions that have no + UUID yet), as well as the disk as a whole are hashed cryptographically from a common seed value. This + seed value is usually the + machine-id5 of the + system, so that the machine ID reproducibly determines the UUIDs assigned to all partitions. If the + machine ID cannot be read (or the user passes , see below) the seed is + generated randomly instead, so that the partition UUIDs are also effectively random. The seed value may + also be set explicitly, formatted as UUID via the option. By hashing these UUIDs + from a common seed images prepared with this tool become reproducible and the result of the algorithm + above deterministic. + + + + Options + + The following options are understood: + + + + + Takes a boolean. If this switch is not specified is + the implied default. Controls whether systemd-repart executes the requested + re-partition operations or whether it should only show what it would do. Unless + is specified systemd-repart will not actually + touch the device's partition table. + + + + + Takes one of refuse, allow, + require or force. Controls how to operate on block devices that + are entirely empty, i.e. carry no partition table/disk label yet. If this switch is not specified the + implied default is refuse. + + If refuse systemd-repart requires that the block device + it shall operate on already carries a partition table and refuses operation if none is found. If + allow the command will extend an existing partition table or create a new one if + none exists. If require the command will create a new partition table if none + exists so far, and refuse operation if one already exists. If force it will create + a fresh partition table unconditionally, erasing the disk fully in effect. If + force no existing partitions will be taken into account or survive the + operation. Hence: use with care, this is a great way to lose all your data. + + + + + + Takes a boolean. If this switch is not specified is + the implied default. Controls whether to issue the BLKDISCARD I/O control + command on the space taken up by any added partitions or on the space in between them. Usually, it's + a good idea to issue this request since it tells the underlying hardware that the covered blocks + shall be considered empty, improving performance. + + + + + + Takes boolean. If this switch is not specified is + the implied default. Controls whether to operate in "factory reset" mode, see above. If set to true + this will remove all existing partitions marked with FactoryReset= set to yes + early while executing the re-partitioning algorithm. Use with care, this is a great way to lose all + your data. Note that partition files need to explicitly turn FactoryReset= on, as + the option defaults to off. If no partitions are marked for factory reset this switch has no + effect. Note that there are two other methods to request factory reset operation: via the kernel + command line and via an EFI variable, see above. + + + + + + If this switch is specified the disk is not re-partitioned. Instead it is determined + if any existing partitions are marked with FactoryReset=. If there are the tool + will exit with exit status zero, otherwise non-zero. This switch may be used to quickly determine + whether the running system supports a factory reset mechanism built on + systemd-repart. + + + + + + Takes a path to a directory to use as root file system when searching for + repart.d/*.conf files and for the machine ID file to use as seed. By default + when invoked on the regular system this defaults to the host's root file system + /. If invoked from the initial RAM disk this defaults to + /sysroot/, so that the tool operates on the configuration and machine ID stored + in the root file system later transitioned into itself. + + + + + + Takes a UUID as argument or the special value random. If a UUID + is specified the UUIDs to assign to partitions and the partition table itself are derived via + cryptographic hashing from it. If not specified it is attempted to read the machine ID from the host + (or more precisely, the root directory configured via ) and use it as seed + instead, falling back to a randomized seed otherwise. Use to force a + randomized seed. Explicitly specifying the seed may be used to generated strictly reproducible + partition tables. + + + + + + Takes a boolean argument. If this switch is not specified, it defaults to on when + called from an interactive terminal and off otherwise. Controls whether to show a user friendly table + and graphic illustrating the changes applied. + + + + + + Takes a file system path. If specified the *.conf are directly + read from the specified directory instead of searching in + /usr/lib/repart.d/*.conf, /etc/repart.d/*.conf, + /run/repart.d/*.conf. + + + + + + + + + See Also + + systemd1, + repart.d5, + machine-id5 + + + +