dracut
======
Harald Hoyer <harald@redhat.com>
-v2.0, March 2011
+v3.0, October 2013
:language: bash
initialized and a user-space helper started to paint animations onto the display
in lockstep with the boot process.
-* If the root file system is on NFS, dracut does then:
+* If the root file system is on NFS, dracut does then:
** Bring up the primary network interface.
** Invoke a DHCP client, with which it can obtain a DHCP lease.
** Extract the name of the NFS share and the address of the NFS server from the
rotated away. Instead, it is simply emptied and the final root file system
mounted over the top.
-= User Manual
-
-== Creating an initramfs Image
-To create a initramfs image, the most simple command is:
-----
-# dracut
-----
-
-This will generate a general purpose initramfs image, with all possible
-functionality resulting of the combination of the installed dracut modules and
-system tools. The image is /boot/initramfs-_++<kernel version>++_.img and
-contains the kernel modules of the currently active kernel with version
-_++<kernel version>++_.
-
-If the initramfs image already exists, dracut will display an error message, and
-to overwrite the existing image, you have to use the --force option.
-----
-# dracut --force
-----
-
-If you want to specify another filename for the resulting image you would issue
-a command like:
-----
-# dracut foobar.img
-----
-
-To generate an image for a specific kernel version, the command would be:
-----
-# dracut foobar.img 2.6.40-1.rc5.f20
-----
-
-A shortcut to generate the image at the default location for a specific kernel
-version is:
-----
-# dracut '' 2.6.40-1.rc5.f20
-----
-
-If you want to create lighter, smaller initramfs images, you may want to specify
-the --host-only or -H option. Using this option, the resulting image will
-contain only those dracut modules, kernel modules and filesystems, which are
-needed to boot this specific machine. This has the drawback, that you can't put
-the disk on another controller or machine, and that you can't switch to another
-root filesystem, without recreating the initramfs image. The usage of the
---host-only option is only for experts and you will have to keep the broken
-pieces. At least keep a copy of a general purpose image (and corresponding
-kernel) as a fallback to rescue your system.
-
-=== Inspecting the Contents
-To see the contents of the image created by dracut, you can use the lsinitrd tool.
-----
-# lsinitrd /boot/initramfs-$(uname -r).img | less
-----
-
-To display the contents of a file in the initramfs also use the lsinitrd tool:
-----
-# lsinitrd /boot/initramfs-$(uname -r).img /etc/ld.so.conf
-include ld.so.conf.d/*.conf
-----
-
-=== Adding dracut Modules
-Some dracut modules are turned off by default and have to be activated manually.
-You can do this by adding the dracut modules to the configuration file
-_/etc/dracut.conf_ or _/etc/dracut.conf.d/myconf.conf_. See <<dracutconf5>>.
-You can also add dracut modules on the command line
-by using the -a or --add option:
-----
-# dracut --add bootchart initramfs-bootchart.img
-----
-
-To see a list of available dracut modules, use the --list-modules option:
-----
-# dracut --list-modules
-----
-
-or, if you have a dracut version earlier than +008+, issue the command:
-----
-# for mod in /usr/lib/dracut/modules.d/*; do echo ${mod##*/??}; done
-----
-
-=== Omitting dracut Modules
-Sometimes you don't want a dracut module to be included for reasons of speed,
-size or functionality. To do this, either specify the omit_dracutmodules
-variable in the _dracut.conf_ or _/etc/dracut.conf.d/myconf.conf_ configuration
-file (see <<dracutconf5>>), or use the -o or --omit option
-on the command line:
-----
-# dracut -o "multipath lvm" no-multipath-lvm.img
-----
-
-=== Adding Kernel Modules
-If you need a special kernel module in the initramfs, which is not
-automatically picked up by dracut, you have the use the --add-drivers option
-on the command line or the drivers vaiable in the _/etc/dracut.conf_
-or _/etc/dracut.conf.d/myconf.conf_ configuration file (see <<dracutconf5>>):
-----
-# dracut --add-drivers mymod initramfs-with-mymod.img
-----
-
-== Boot parameters
-The generated initramfs.img file normally does not contain any system
-configuration files (except for some special exceptions), so the configuration
-has to be done on the kernel command line. With this flexibility, you can easily
-boot from a changed root partition, without the need to recompile the initramfs
-image. So, you could completly change your root partition (move it inside a md
-raid with encryption and LVM on top), as long as you specify the correct
-filesystem LABEL or UUID on the kernel command line for your root device, dracut
-will find it and boot from it.
-
-The kernel command line usually can be configured in _/boot/grub/grub.conf_, if
-grub is your bootloader and it also can be edited in the real boot process in
-the grub menu.
-
-The kernel command line can also be provided by the dhcp server with the
-root-path option. See <<NetworkBoot>>.
-
-For a full reference of all kernel command line parameters, see <<dracut8>>.
-
-=== Specifying the root Device
-This is the only option dracut really needs to boot from your root partition.
-Because your root partition can live in various environments, there are a lot of
-formats for the root= option. The most basic one is root=_++<path to device
-node>++_:
-----
-root=/dev/sda2
-----
-
-Because device node names can change, dependent on the drive ordering, you are
-encouraged to use the filesystem identifier (UUID) or filesystem label (LABEL)
-to specify your root partition:
-----
-root=UUID=19e9dda3-5a38-484d-a9b0-fa6b067d0331
-----
-
-or
-
-----
-root=LABEL=myrootpartitionlabel
-----
-
-To see all UUIDs or LABELs on your system, do:
-----
-# ls -l /dev/disk/by-uuid
-----
-
-or
-
-----
-# ls -l /dev/disk/by-label
-----
-
-If your root partition is on the network see <<NetworkBoot>>.
-
-=== Keyboard Settings
-If you have to input passwords for encrypted disk volumes, you might want to set
-the keyboard layout and specify a display font.
-
-A typical german kernel command would contain:
-----
-vconsole.font=latarcyrheb-sun16 vconsole.keymap=de-latin1-nodeadkeys locale.LANG=de_DE.UTF-8
-----
-
-Setting these options can override the setting stored on your system, if you use
-a modern init system, like systemd.
-
-For dracut versions prior to version +008+ the line would look like:
-----
-LANG=de_DE.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=de-latin1-nodeadkeys
-----
-
-=== Blacklisting Kernel Modules
-Sometimes it is required to prevent the automatic kernel module loading of a
-specific kernel module. To do this, just add rd.blacklist=_++<kernel module
-name>++_, with _++<kernel module name>++_ not containing the _.ko_
-suffix, to the kernel command line. For example:
-----
-rd.driver.blacklist=mptsas rd.driver.blacklist=nouveau
-----
-
-The option can be specified multiple times on the kernel command line.
-
-=== Speeding up the Boot Process
-If you want to speed up the boot process, you can specify as much information
-for dracut on the kernel command as possible. For example, you can tell dracut,
-that you root partition is not on a LVM volume or not on a raid partition, or
-that it lives inside a specific crypto LUKS encrypted volume. By default, dracut
-searches everywhere. A typical dracut kernel command line for a plain primary or
-logical partition would contain:
-----
-rd.luks=0 rd.lvm=0 rd.md=0 rd.dm=0
-----
-
-On systems with dracut version prior to +008+ the line would look like:
-----
-rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM
-----
-
-This turns off every automatic assembly of LVM, MD raids, DM raids and crypto LUKS.
-
-Of course, you could also omit the dracut modules in the initramfs creation
-process, but then you would lose the posibility to turn it on on demand.
-
-
-[[Injecting]]
-=== Injecting custom Files
-To add your own files to the initramfs image, you have several possibilities.
-
-The --include option let you specify a source path and a target path. For example
-----
-# dracut --include cmdline-preset /etc/cmdline initramfs-cmdline-pre.img
-----
-will create an initramfs image, where the file cmdline-preset will be copied
-inside the initramfs to _/etc/cmdline_. --include can only be specified once.
-
-
-----
-# mkdir rd.live.overlay
-# mkdir rd.live.overlay/etc
-# mkdir rd.live.overlay/etc/conf.d
-# echo "ip=auto" >> rd.live.overlay/etc/cmdline
-# echo export TESTVAR=testtest >> rd.live.overlay/etc/conf.d/testvar.conf
-# echo export TESTVAR=testtest >> rd.live.overlay/etc/conf.d/testvar.conf
-# tree rd.live.overlay/
-rd.live.overlay/
-└── etc
- ├── cmdline
- └── conf.d
- └── testvar.conf
-# dracut --include rd.live.overlay / initramfs-rd.live.overlay.img
-----
-
-This will put the contents of the rd.live.overlay directory into the root of the
-initramfs image.
-
-The --install option let you specify several files, which will get installed in
-the initramfs image at the same location, as they are present on initramfs
-creation time.
-
-
-----
-# dracut --install 'strace fsck.ext3 ssh' initramfs-dbg.img
-----
-
-This will create an initramfs with the strace, fsck.ext3 and ssh executables,
-together with the libraries needed to start those. The --install option can be
-specified multiple times.
-
-
-[[NetworkBoot]]
-== Network Boot
-
-If your root partition is on a network drive, you have to have the network
-dracut modules installed to create a network aware initramfs image.
-
-On a Red Hat Enterprise Linux or Fedora system, this means, you have to install
-the _dracut-network_ rpm package:
-
-
-----
-# yum install dracut-network
-----
-
-The resulting initramfs image can be served by a boot manager residing on your
-local hard drive or it can be served by a PXE/TFTP server.
-
-How to setup your PXE/TFTP server can be found in the
-http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/[Red
-Hat Enterprise Linux Storage Administration Guide].
-
-If you specify rd.ip=auto on the kernel command line, then dracut asks a dhcp
-server about the ip adress for the machine. The dhcp server can also serve an
-additional root-path, which will set the root device for dracut. With this
-mechanism, you have static configuration on your client machine and a
-centralized boot configuration on your TFTP/DHCP server. If you can't pass a
-kernel command line, then you can inject _/etc/cmdline_, with a method described
-in <<Injecting>>.
-
-
-
-
-=== Reducing the Image Size
-
-To reduce the size of the initramfs, you should create it with by ommitting all
-dracut modules, which you know, you don't need to boot the machine.
-
-You can also specify the exact dracut and kernel modules to produce a very tiny
-initramfs image.
-
-For example for a NFS image, you would do:
-
-
-----
-# dracut -m "nfs network base" initramfs-nfs-only.img
-----
-
-Then you would boot from this image with your target machine and reduce the size
-once more by creating it on the target machine with the --host-only option:
-
-
-----
-# dracut -m "nfs network base" --host-only initramfs-nfs-host-only.img
-----
-
-This will reduce the size of the initramfs image significantly.
-
-
-
-=== NFS Root Device
-
-FIXME
-
-=== iSCSI Root Device
-
-FIXME
-
-=== FCoE Root Device
-
-FIXME
-
-== Troubleshooting
-
-If the boot process does not succeed, you have several options to debug the
-situation. Some of the basic operations are covered here. For more information
-you should also visit:
-http://fedoraproject.org/wiki/How_to_debug_Dracut_problems
-
-
-[[identifying-your-problem-area]]
-=== Identifying your problem area
-. Remove ''rhgb'' and ''quiet'' from the kernel command line
-. Add ''rd.shell'' to the kernel command line. This will present a shell should
-dracut be unable to locate your root device
-. Add ''rd.shell rd.debug log_buf_len=1M'' to the kernel command line so that
-dracut shell commands are printed as they are executed
-. With dracut >= 002-11, you can inspect the rd.debug output with:
-+
-----
-# less /run/initramfs/init.log
-# dmesg | less
-----
-
-[[information-to-include-in-your-report]]
-=== Information to include in your report
-
-[[all-bug-reports]]
-==== All bug reports
-In all cases, the following should be mentioned and attached to your bug report:
-
-* The exact kernel command-line used. Typically from the bootloader
-configuration file (e.g. _/etc/grub.conf_) or from _/proc/cmdline_.
-* A copy of your disk partition information from _/etc/fstab_, which might be
-obtained booting an old working initramfs or a rescue medium.
-* A device listing from device-mapper. This can be obtained by running the
-command
-+
-----
-# dmsetup ls --tree
-----
-+
-* A list of block device attributes. This can be obtained by running the commands:
-+
-----
-# blkid -p
-# blkid -p -o udev
-----
-* Turn on dracut debugging (see _the 'debugging dracut' section_), and attach
-all relevant information from the boot log. This can be obtained by running the
-command
-+
-----
-# dmesg|grep dracut
-----
-+
-* If you use a dracut configuration file, please include _/etc/dracut.conf_ and
-all files in _/etc/dracut.conf.d/*.conf_
-
-[[logical-volume-management-related-problems]]
-==== Logical Volume Management related problems
-As well as the information from <<all-bug-reports>> include the following
-information:
-
-* Include physical volume information by running the command:
-+
-----
-# lvm pvdisplay
-----
-+
-* Include volume group information by running the command:
-+
-----
-# lvm vgdisplay
-----
-+
-* Include logical volume information by running the command:
-+
-----
-# lvm lvdisplay
-----
-
-[[software-raid-related-problems]]
-==== Software RAID related problems
-As well as the information from <<all-bug-reports>>, include the following
-information:
-
-* If using software RAID disk partitions, please include the output of
-+
-----
-# cat /proc/mdstat
-----
-
-[[network-root-device-related-problems]]
-==== Network root device related problems
-This section details information to include when experiencing problems on a
-system whose root device is located on a network attached volume (e.g. iSCSI,
-NFS or NBD). As well as the information from <<all-bug-reports>>, include the
-following information:
-
-
-* Please include the output of
-+
-----
-# /sbin/ifup <interfacename>
-# ip addr show
-----
-
-[[debugging-dracut]]
-=== Debugging dracut
-
-
-[[configure-a-serial-console]]
-==== Configure a serial console
-
-Successfully debugging dracut will require some form of console
-logging during the system boot. This section documents configuring a
-serial console connection to record boot messages.
-
-. First, enable serial console output for both the kernel and the bootloader.
-. Open the file _/etc/grub.conf_ for editing. Below the line ''timeout=5'', add
-the following:
-+
-----
-serial --unit=0 --speed=9600
-terminal --timeout=5 serial console
-----
-+
-. Also in _/etc/grub.conf_, add the following boot arguemnts to the ''kernel''
-line:
-+
-----
-console=tty0 console=ttyS0,9600
-----
-+
-. When finished, the _/etc/grub.conf_ file should look similar to the example
-below.
-+
-----
-default=0
-timeout=5
-serial --unit=0 --speed=9600
-terminal --timeout=5 serial console
-title Fedora (2.6.29.5-191.fc11.x86_64)
- root (hd0,0)
- kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 console=ttyS0,9600
- initrd /dracut-2.6.29.5-191.fc11.x86_64.img
-----
-+
-. More detailed information on how to configure the kernel for console output
-can be found at
-http://www.faqs.org/docs/Linux-HOWTO/Remote-Serial-Console-HOWTO.html#CONFIGURE-KERNEL.
-. Redirecting non-interactive output
-+
---
-NOTE: You can redirect all non-interactive output to _/dev/kmsg_ and the kernel
-will put it out on the console when it reaches the kernel buffer by doing
-
-----
-# exec >/dev/kmsg 2>&1 </dev/console
-----
---
-
-[[using-the-dracut-shell]]
-==== Using the dracut shell
-
-Dracut offers a shell for interactive debugging in the event dracut fails to
-locate your root filesystem. To enable the shell:
-
-. Add the boot parameter ''rd.shell'' to your bootloader configuration file
-(e.g. _/etc/grub.conf_)
-. Remove the boot arguments ''rhgb'' and ''quiet''
-+
-A sample _/etc/grub.conf_ bootloader configuration file is listed below.
-+
-----
-default=0
-timeout=5
-serial --unit=0 --speed=9600
-terminal --timeout=5 serial console
-title Fedora (2.6.29.5-191.fc11.x86_64)
- root (hd0,0)
- kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 rd.shell
- initrd /dracut-2.6.29.5-191.fc11.x86_64.img
-----
-+
-. If system boot fails, you will be dropped into a shell as seen in the example below.
-+
-----
-No root device found
-Dropping to debug shell.
-
-#
-----
-+
-. Use this shell prompt to gather the information requested above (see <<all-bug-reports>>).
-
-[[accessing-the-root-volume-from-the-dracut-shell]]
-==== Accessing the root volume from the dracut shell
-From the dracut debug shell, you can manually perform the task of locating and
-preparing your root volume for boot. The required steps will depend on how your
-root volume is configured. Common scenarios include:
-
-* A block device (e.g. _/dev/sda7_)
-* A LVM logical volume (e.g. _/dev/VolGroup00/LogVol00_)
-* An encrypted device (e.g. _/dev/mapper/luks-4d5972ea-901c-4584-bd75-1da802417d83_)
-* A network attached device (e.g. netroot=iscsi:@192.168.0.4::3260::iqn.2009-02.org.fedoraproject:for.all)
-
-The exact method for locating and preparing will vary. However, to continue with
-a successful boot, the objective is to locate your root volume and create a
-symlink _/dev/root_ which points to the file system. For example, the following
-example demonstrates accessing and booting a root volume that is an encrypted
-LVM Logical volume.
-
-. Inspect your partitions using parted
-+
-----
-# parted /dev/sda -s p
-Model: ATA HTS541060G9AT00 (scsi)
-Disk /dev/sda: 60.0GB
-Sector size (logical/physical): 512B/512B
-Partition Table: msdos
-Number Start End Size Type File system Flags
-1 32.3kB 10.8GB 107MB primary ext4 boot
-2 10.8GB 55.6GB 44.7GB logical lvm
-----
-+
-. You recall that your root volume was a LVM logical volume. Scan and activate
-any logical volumes.
-+
-----
-# lvm vgscan
-# lvm vgchange -ay
-----
-+
-. You should see any logical volumes now using the command blkid:
-+
-----
-# blkid
-/dev/sda1: UUID="3de247f3-5de4-4a44-afc5-1fe179750cf7" TYPE="ext4"
-/dev/sda2: UUID="Ek4dQw-cOtq-5MJu-OGRF-xz5k-O2l8-wdDj0I" TYPE="LVM2_member"
-/dev/mapper/linux-root: UUID="def0269e-424b-4752-acf3-1077bf96ad2c" TYPE="crypto_LUKS"
-/dev/mapper/linux-home: UUID="c69127c1-f153-4ea2-b58e-4cbfa9257c5e" TYPE="ext3"
-/dev/mapper/linux-swap: UUID="47b4d329-975c-4c08-b218-f9c9bf3635f1" TYPE="swap"
-----
-+
-. From the output above, you recall that your root volume exists on an encrypted
-block device. Following the guidance disk encryption guidance from the
-Installation Guide, you unlock your encrypted root volume.
-+
-----
-# UUID=$(cryptsetup luksUUID /dev/mapper/linux-root)
-# cryptsetup luksOpen /dev/mapper/linux-root luks-$UUID
-Enter passphrase for /dev/mapper/linux-root:
-Key slot 0 unlocked.
-----
-+
-. Next, make a symbolic link to the unlocked root volume
-+
-----
-# ln -s /dev/mapper/luks-$UUID /dev/root
-----
-+
-. With the root volume available, you may continue booting the system by exiting
-the dracut shell
-+
-----
-# exit
-----
-
-[[additional-dracut-boot-parameters]]
-==== Additional dracut boot parameters
-For more debugging options, see <<dracutkerneldebug>> in <<dracutcmdline7>>.
-
-= Developer Manual
-
-== dracut Components
-
-dracut uses a modular system to build and extend the initramfs image. All
-modules are located in _/usr/lib/dracut/modules.d_ or in _<git-src>/modules.d_.
-The most basic dracut module is _99base_. In _99base_ the initial shell script
-init is defined, which gets run by the kernel after initramfs loading. Although
-you can replace init with your own version of _99base_, this is not encouraged.
-Instead you should use, if possible, the hooks of dracut. All hooks, and the
-point of time in which they are executed, are described in <<stages>>.
-
-The main script, which creates the initramfs is dracut itsself. It parses all
-arguments and sets up the directory, in which everything is installed. It then
-executes all check, install, installkernel scripts found in the modules, which
-are to be processed. After everything is installed, the install directory is
-archived and compressed to the final initramfs image. All helper functions used
-by check, install and installkernel are found in in the file _dracut-functions_.
-These shell functions are available to all module installer (install,
-installkernel) scripts, without the need to source _dracut-functions_.
-
-A module can check the preconditions for install and installkernel with the
-check script. Also dependencies can be expressed with check. If a module passed
-check, install and installkernel will be called to install all of the necessary
-files for the module. To split between kernel and non-kernel parts of the
-installation, all kernel module related parts have to be in installkernel. All
-other files found in a module directory are module specific and mostly are hook
-scripts and udev rules.
-
-
-[[stages]]
-== Boot Process Stages
-
-The init script in _99base_ is the main script, which prepares the root file
-system for usage, runs udev, mounts the real root device, kills the remaining
-processes, and switches to the real root device for further booting. dracut
-modules can insert custom script at various points, to control the boot process.
-These hooks are plain directories containing shell scripts ending with ".sh",
-which are sourced by init.
-Common used functions are in _dracut-lib.sh_, which can be sourced by any script.
-
-
-
-=== Basic Setup
-
-The first thing init does, is to mount _/proc_ and _/sys_ and manually create
-the basic device nodes and symbolic links in _/dev_ needed to execute basic
-commands. Then logging is setup according to kernel command line arguments.
-_/dev/pts_ and _/dev/shm_ are mounted and the first hook is sourced.
-
-
-
-=== Hook: cmdline
+If the systemd module is used in the initramfs, the ordering of the services
+started looks like <<dracutbootup7>>.
-The _cmdline_ hook is a place to insert scripts to parse the kernel command line
-and prepare the later actions, like setting up udev rules and configuration
-files.
+== Dracut on shutdown
-In this hook the most important environment variable is defined: root. The
-second one is rootok, which indicates, that a module claimed to be able to parse
-the root defined. So for example, **root=**__iscsi:....__ will be claimed by the
-iscsi dracut module, which then sets rootok.
+On a systemd driven system, the dracut initramfs is also used for the shutdown
+procedure.
-=== Hook: pre-udev
+The following steps are executed during a shutdown:
-This hook is executed right after the cmdline hook and a check if root and
-rootok were set. Here modules can take action with the final root, and before
-udev has been run.
+* systemd switches to the shutdown.target
+* systemd starts
+ $prefix/lib/systemd/system/shutdown.target.wants/dracut-shutdown.service
+* dracut-shutdown.service executes /usr/lib/dracut/dracut-initramfs-restore
+ which unpacks the initramfs to /run/initramfs
+* systemd finishes shutdown.target
+* systemd kills all processes
+* systemd tries to unmount everything and mounts the remaining read-only
+* systemd checks, if there is a /run/initramfs/shutdown executable
+* if yes, it does a pivot_root to /run/initramfs and executes ./shutdown.
+ The old root is then mounted on /oldroot.
+ /usr/lib/dracut/modules.d/99shutdown/shutdown.sh is the shutdown executable.
+* shutdown will try to umount every /oldroot mount and calls the various
+ shutdown hooks from the dracut modules
+This ensures, that all devices are disassembled and unmounted cleanly.
-
-=== Start Udev
-
-Now udev is started and the logging for udev is setup.
-
-
-
-=== Hook: pre-trigger
-
-In this hook, you can set udev environment variables with **udevadm control
---property=KEY=_value_** or control the further execution of udev with
-udevadm.
-
-
-
-=== Trigger Udev
-
-udev is triggered by calling udevadm trigger, which sends add events for all
-devices and subsystems.
-
-
-
-=== Main Loop
-
-Now the main loop of 99base/init begins. Here we loop until udev has settled and
-all scripts in _initqueue/finished_ returned true. In this loop there are three
-hooks, where scripts can be inserted by calling /sbin/initqueue.
-
-
-
-==== Initqueue
-
-This hook gets executed every time a script is inserted here, regardless of the
-udev state.
-
-
-
-==== Initqueue settled
-
-This hooks gets executed every time udev has settled.
-
-
-
-==== Initqueue timeout
-
-This hooks gets executed, when the main loop counter becomes half of the
-rd.retry counter.
-
-
-
-==== Initqueue finished
-
-This hook is called after udev has settled and if all scripts herein return 0
-the main loop will be ended.
-
-
-
-=== Hook: pre-mount
-
-Before the root device is mounted all scripts in the hook pre-mount are
-executed. In some cases (e.g. NFS) the real root device is already mounted,
-though.
-
-
-
-=== Hook: mount
-
-This hook is mainly to mount the real root device.
-
-
-
-=== Hook: pre-pivot
-
-This hook is called before cleanup hook, This is a good place for
-actions other than cleanups which need to be called before pivot.
-
-
-=== Hook: cleanup
-
-This hook is the last hook and is called before init finally switches root to
-the real root device. This is a good place to clean up and kill processes not
-needed anymore.
-
-
-=== Cleanup and switch_root
-
-Init kills all udev processes, cleans up the environment, sets up the arguments
-for the real init process and finally calls switch_root. switch_root removes the
-whole filesystem hierarchy of the initramfs, chroot()s to the real root device
-and calls /sbin/init with the specified arguments.
-
-To ensure all files in the initramfs hierarchy can be removed, all processes
-still running from the initramfs should not have any open file descriptors left.
-
-
-
-== Network Infrastructure
-
-
-FIXME
-
-
-== Writing a Module
-
-A simple example module is _96insmodpost_, which modprobes a kernel module after
-udev has settled and the basic device drivers have been loaded.
-
-All module installation information is in the file module-setup.sh.
-
-First we create a check() function, which just exits with 0 indicating that this
-module should be included by default.
-
-check():
-
-
-----
-return 0
-----
-
-The we create the install() function, which installs a cmdline hook with
-priority number 20 called _parse-insmodpost.sh_. It also installs the
-_insmodpost.sh_ script in _/sbin_.
-
-install():
-
-
-----
-inst_hook cmdline 20 "$moddir/parse-insmodpost.sh"
-inst_simple "$moddir/insmodpost.sh" /sbin/insmodpost.sh
-----
-
-The _pase-instmodpost.sh_ parses the kernel command line for a argument
-rd.driver.post, blacklists the module from being autoloaded and installs the
-hook _insmodpost.sh_ in the _initqueue/settled_.
-
-_parse-insmodpost.sh_:
-
-
-----
-for p in $(getargs rd.driver.post=); do
- echo "blacklist $p" >> /etc/modprobe.d/initramfsblacklist.conf
- _do_insmodpost=1
-done
-
-[ -n "$_do_insmodpost" ] && /sbin/initqueue --settled --unique --onetime /sbin/insmodpost.sh
-unset _do_insmodpost
-
-----
-
-_insmodpost.sh_, which is called in the _initqueue/settled_ hook will just
-modprobe the kernel modules specified in all rd.driver.post kernel command line
-parameters. It runs after udev has settled and is only called once (--onetime).
-
-_insmodpost.sh_:
-
-
-----
-. /lib/dracut-lib.sh
-
-for p in $(getargs rd.driver.post=); do
- modprobe $p
-done
-
-----
-
-
-
-=== check()
-
-_check()_ is called by dracut to evaluate the inclusion of a dracut module in
-the initramfs.
-
-$hostonly:: If the $hostonly variable is set, then the module check() function
-should be in "hostonly" mode, which means, that the check() should only return
-0, if the module is really needed to boot this specific host.
-
-check() should return with:
-
-0:: Include the dracut module in the initramfs.
-
-1:: Do not include the dracut module. The requirements are not fullfilled
-(missing tools, etc.)
-
-255:: Only include the dracut module, if another module requires it or if
-explicitly specified in the config file or on the argument list.
-
-
-
-=== depends()
-
-The function depends() should echo all other dracut module names the module
-depends on.
-
-
-
-=== install()
-
-dracut_install
-
-inst
-
-inst_hook
-
-inst_rules
-
-
-
-
-
-=== installkernel()
-
-instmods
-
-
-
-=== Creation Functions
-
-
-FIXME
-
-
-=== Initramfs Functions
-
-
-FIXME
-
-
-=== Network Modules
-
-FIXME
-
+= User Manual
:leveloffset: 1
-[[dracut8]]
include::dracut.8.asc[]
+:leveloffset: 1
[[dracutconf5]]
include::dracut.conf.5.asc[]
[[mkinitrd8]]
include::mkinitrd.8.asc[]
+= Developer Manual
+
+:leveloffset: 1
+[[dracutmodules7]]
+include::dracut.modules.7.asc[]
+
+[[dracutbootup7]]
+include::dracut.bootup.7.asc[]
+
:leveloffset: 0
[appendix]
License