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Boom

Boom is a boot manager for Linux systems using boot loaders that support the BootLoader Specification for boot entry configuration. It is based on the boot manager design discussed in the Boot-to-snapshot design v0.6 document.

Boom requires a BLS compatible boot loader to function: either the systemd-boot project, or Grub2 with the bls patch (Red Hat Grub2 builds include this support in both Red Hat Enterprise Linux 7 and Fedora).

Boom allows for flexible boot configuration and simplifies the creation of new or modified boot entries: for example to boot snapshot images of the system created using LVM2 or BTRFS.

Boom does not modify the existing boot loader configuration (other than to insert the additional entries managed by boom - see Grub2 Integration): the existing boot configuration is maintained and any distribution integration (e.g. kernel installation and update scripts) will continue to function as before.

Boom aims to be a simple and extensible, and to be able to create boot configurations for a wide range of Linux system configurations and boot parameters.

This project is hosted at:

For the latest version, to contribute, and for more information, please visit the project pages or join the mailing list.

To clone the current master (development) branch run:

git clone git://github.com/bmr-cymru/boom.git

Reporting bugs

Please report bugs via the mailing list or by opening an issue in the GitHub Issue Tracker

Mailing list

The dm-devel is the mailing list for any boom-related questions and discussion. Patch submissions and reviews are welcome too.

Building and installing Boom

A setuptools based build script is provided: local installations and package builds can be performed by running python setup.py and a setup command. See python setup.py --help for detailed information on the available options and commands.

Builds and packages

Binary packages for Fedora and Red Hat Enterprise Linux are available from the copr repository. These builds use the RPM spec file distributed in the git repository and include all the necessary library modules, binaries, and configuration files needed to install and use boom.

To enable the repository on Fedora, run:

# dnf copr enable bmr/boom

The python2 and python3 versions of boom may be installed by running:

# dnf -y install python2-boom python3-boom

Note that although both python 2 and 3 versions of the library are provided only one package contains the boom binary, depending on the system default python runtime for that distribution version.

The boom command

The boom command is the main interface to the boom boot manager. It is able to create, delete, edit and display boot entries, operating system and host profiles and provides reports showing the available profiles and entries, and their configurations.

Boom commands normally operate on a particular object type: a boot entry, a host profile or an OS profile. Commands are also provided to manipulate legacy boot loader configurations (for systems that do not natively support the BLS standard).

# boom [entry] <command> <options> # `BootEntry` command

# boom profile <command> <options> # `OsProfile` command

# boom hostprofile <command> <options> # `HostProfile` command

# boom legacy <command> <options> # Legacy boot loader commands

If no command type is given entry is assumed.

Profiles and Boot Entries

The two main object types in boom are the Profile and BootEntry. Profiles support tailoring boot entry configuration to either a specific operating system distribution (OsProfile), or a specific installation (HostProfile, based on the system machine-id).

Boom stores boot loader entries (BootEntry) in the system BLS loader directory - normally /boot/loader/entries.

Boom OsProfile files are stored in the boom configuration directory, /boot/boom/profiles and HostProfile data is found in /boot/boom/hosts.

The location of the boot file system may be overridden using the --boot-dir command line option and the location of both the boot file system and boom configuration directory may be overridden by calling the boom.set_boot_path() and boom.set_boom_path() functions.

These options are primarily of use for testing, or for working with boom data from a system other than the running host.

Boom configuration data is stored in the /boot file system to permit the tool to be run from any booted instance of any installed operating system.

OsProfile

An OsProfile stores identity information and templates used to write bootloader configurations for an instance of an operating system. The identity is based on values from the /etc/os-release file, and the available templates allow customisation of the kernel and initramfs images, kernel options and other properties required to boot an instance of that OS.

A set of OsProfile files can be pre-installed with boom, or generated using the command line tool.

An OsProfile is uniquely identified by its OS Identifier, or os_id, a SHA2 hash computed on the OsProfile identity fields. All SHA identifiers are displayed by default using the minimum width necessary to ensure uniqueness: all command line arguments accepting an identifier also accept any unique prefix of a valid identifier.

OsProfile templates

The template properties of an OsProfile (kernel pattern, initramfs pattern, LVM2 and BTRFS root options and kernel command line options) may include format strings that are expanded when creating a new BootEntry.

The available keys are:

  • %{version} - the kernel version
  • %{lvm_root_lv} - the LVM2 logical volume containing the root file system in vg/lv notation.
  • %{btrfs_subvol_id} - the BTRFS subvolume identifier to use.
  • %{btrfs_subvol_path} - the BTRFS subvolume path to use.
  • %{root_device} - The system root device, relative to /.
  • %{options} - Kernel command line options, including the root device specification and options.

Default template values are supplied when creating a new OsProfile; these can be overridden by specifying alternate values on the command line. The defaults are suitable for most Linux operating systems but can be customised to allow for particular OS requirements, or to set custom behaviours.

HostProfile

A HostProfile provides an additional means to customise the boot configuration on a per-installation basis. Use of host profiles is optional: if no HostProfile exits for a given host then the default values from the corresponding OsProfile are used.

Values specified in a Boom HostProfile are automatically applied whenever a boot entry for the corresponding machine-id is created or edited. Multiple Boom HostProfile templates can be defined for a given system and distinguished by a label: for example 'production', 'debug' or other profile labels used to identify and group commonly-used sets of boot options.

Host profiles can be used to add or remove kernel command line options, or to modify existing template values provided by the OsProfile (including the location and naming of the kernel, initramfs and other boot images). This can be used to automatically apply settings where required, for example adding nomodeset or other kernel command line parameters if required for that installation, or modifying the command line to enable or disable debugging, logging or storage activation options.

Like the OsProfile, a HostProfile is uniquely identified by a HostId identifier.

BootEntry

A BootEntry is an individual bootloader entry for one instance of an operating system. It includes all the parameters required for the boot loader to load the OS, and for the kernel and user space to boot the environment (including configuration of LVM2 logical volumes and BTRFS subvolumes).

The BootEntry stored on-disk is generated from the templates stored in an associated OsProfile and boot parameters configuration provided by command line arguments.

Boom uses BLS0 notation as the canonical format for the boot entry store.

An BootEntry is uniquely identified by its Boot Identifier, or boot_id, a SHA2 hash computed on the BootEntry boot parameter fields (note that this means that changing the parameters of an existing BootEntry will also change its boot_id. All SHA identifiers are displayed by default using the minimum width necessary to ensure uniqueness: all command line arguments accepting an identifier also accept any unique prefix of a valid identifier.

Boom subcommands

For both profile and boot entry command types, boom provides six subcommands:

  • create
  • delete --profile OS_ID | --host-profile HOST_ID | --boot-id BOOT_ID [...]
  • clone --profile OS_ID | --host-profile HOST_ID | --boot-id BOOT_ID [...]
  • show
  • list
  • edit

create

Create a new OsProfile HostProfile, or BootEntry using the values entered on the command line.

delete

Delete the specified profile or BootEntry.

clone

Create a new profile or BootEntry by cloning an existing object and modifying its properties. A boot_id, os_id or host_id must be used to select the object to clone. Any remaining command line options modify the newly created object.

show

Display the specified objects in human readable format.

list

List objects matching selection criteria as a tabular report.

edit

Modify an existing profile or BootEntry by changing one or more of its attributes.

It is not possible to change the name, short name, version, or version identifier of an OsProfile using this command, since these fields form the OsProfile identifier: to modify one of these fields use the clone command to create a new profile specifying the attribute to be changed.

When editing a BootEntry, the boot_id will change: this is because the options that define an entry form the entry's identity. The new boot_id is written to the terminal on success.

Reporting commands

The boom entry list and boom host|profile list commands generate a tabular report as output. To control the list of displayed fields use the -o/--options FIELDS argument:

boom list -oboot_id,version
BootId  Version
fb3286f 3.10-1.el7.fc24.x86_64
1031ab0 3.10-23.el7
a559d3a 2.6.32-232.el6
a559d3a 2.6.32-232.el6
2c89556 2.2.2-2.fc24.x86_64
e79db6a 1.1.1-1.fc24.x86_64
d85f2c3 3.10.1-1.el7
2fc3f4f 4.1.1-100.fc24
d85f2c3 3.10.1-1.el7

To add extra fields to the default selection, prefix the field list with the + character:

boom list -o+kernel,initramfs
BootID  Version                  OsID    Name                            OsVersion   Kernel                               Initramfs
fb3286f 3.10-1.el7.fc24.x86_64   3fc389b Red Hat Enterprise Linux Server 7.2 (Maipo) /boot/vmlinuz-3.10-1.el7.fc24.x86_64 /boot/initramfs-3.10-1.el7.fc24.x86_64.img
1031ab0 3.10-23.el7              3fc389b Red Hat Enterprise Linux Server 7.2 (Maipo) /boot/vmlinuz-3.10-23.el7            /boot/initramfs-3.10-23.el7.img
a559d3a 2.6.32-232.el6           98c3edb Red Hat Enterprise Linux Server 6 (Server)  /boot/kernel-2.6.32-232.el6          /boot/initramfs-2.6.32-232.el6.img
a559d3a 2.6.32-232.el6           98c3edb Red Hat Enterprise Linux Server 6 (Server)  /boot/kernel-2.6.32-232.el6          /boot/initramfs-2.6.32-232.el6.img
d85f2c3 3.10.1-1.el7             3fc389b Red Hat Enterprise Linux Server 7.2 (Maipo) /boot/vmlinuz-3.10.1-1.el7           /boot/initramfs-3.10.1-1.el7.img
d85f2c3 3.10.1-1.el7             3fc389b Red Hat Enterprise Linux Server 7.2 (Maipo) /boot/vmlinuz-3.10.1-1.el7           /boot/initramfs-3.10.1-1.el7.img
e19586b 7.7.7                    3fc389b Red Hat Enterprise Linux Server 7.2 (Maipo) /boot/vmlinuz-7.7.7                  /boot/initramfs-7.7.7.img

To display the available fields for either report use the field name help.

BootEntry fields:

boom list -o help
Boot loader entries Fields
--------------------------
  bootid        - Boot identifier [sha]
  title         - Entry title [str]
  options       - Kernel options [str]
  kernel        - Kernel image [str]
  initramfs     - Initramfs image [str]
  machineid     - Machine identifier [sha]

OS profiles Fields
------------------
  osid          - OS identifier [sha]
  osname        - OS name [str]
  osshortname   - OS short name [str]
  osversion     - OS version [str]
  osversion_id  - Version identifier [str]
  unamepattern  - UTS name pattern [str]
  kernelpattern - Kernel image pattern [str]
  initrdpattern - Initrd pattern [str]
  lvm2opts      - LVM2 options [str]
  btrfsopts     - BTRFS options [str]
  options       - Kernel options [str]

Boot parameters Fields
----------------------
  version       - Kernel version [str]
  rootdev       - Root device [str]
  rootlv        - Root logical volume [str]
  subvolpath    - BTRFS subvolume path [str]
  subvolid      - BTRFS subvolume ID [num]

OsProfile fields:

boom profile list -o help
OS profiles Fields
------------------
  osid          - OS identifier [sha]
  osname        - OS name [str]
  osshortname   - OS short name [str]
  osversion     - OS version [str]
  osversion_id  - Version identifier [str]
  unamepattern  - UTS name pattern [str]
  kernelpattern - Kernel image pattern [str]
  initrdpattern - Initrd pattern [str]
  lvm2opts      - LVM2 options [str]
  btrfsopts     - BTRFS options [str]
  options       - Kernel options [str]

HostProfile fields:

boom host list -o help
Host profiles Fields
--------------------
  hostid        - Host identifier [sha]
  machineid     - Machine identifier [sha]
  osid          - OS identifier [sha]
  hostname      - Host name [str]
  label         - Host label [str]
  kernelpattern - Kernel image pattern [str]
  initrdpattern - Initrd pattern [str]
  lvm2opts      - LVM2 options [str]
  btrfsopts     - BTRFS options [str]
  options       - Kernel options [str]
  profilepath   - On-disk profile path [str]
  addopts       - Added Options [str]
  delopts       - Deleted Options [str]

Getting help

Help is available for the boom command and each command line option.

Run the command with --help to display the full usage message:

# boom --help

Configuring Boom

Creating an OsProfile

To automatically generate boot configuration Boom needs an Operating System Profile for the system(s) for which it will create entries.

And OsProfile is a collection of attributes that describe the OS identity and provide templates for boot loader entries.

The identity information comprising an OsProfile is taken from the os-release file for the distribution. Additional properties, such as the UTS release pattern to match for the distribution, are either provided on the boom command line or are set to default values.

To create an OsProfile for the running system, use the -H/--from-host' command line option:

# boom profile create --from-host --uname-pattern fc26
Created profile with os_id d4439b7:
  OS ID: "d4439b7d2f928c39f1160c0b0291407e5990b9e0",
  Name: "Fedora", Short name: "fedora",
  Version: "26 (Workstation Edition)", Version ID: "26",
  UTS release pattern: "fc26",
  Kernel pattern: "/kernel-%{version}", Initramfs pattern: "/initramfs-%{version}.img",
  Root options (LVM2): "rd.lvm.lv=%{lvm_root_lv}",
  Root options (BTRFS): "rootflags=%{btrfs_subvolume}",
  Options: "root=%{root_device} ro %{root_opts}"

The --uname-pattern OsProfile property is an otional but recommended pattern (regular expression) that should match the UTS release (uname) strings reported by the operating system.

The uname pattern is used when an on-disk boot loader entry is found that does not contain an OS identifier (for e.g. a manually edited entry, or one created by a different program).

Creating a HostProfile

Boom can optionally apply further customisation to the boot entries it creates by defining a HostProfile. The host profile can be used to modify the templates (boot image names and paths, boot entry titles, kernel command line options etc) provided by the OsProfile.

To create a new host profile for the current system use the host create command, specifying the parameters to modify. For example, to create a new host profile for a system running Fedora 30 that adds the "debug" kernel command line argument, and removes the "rhgb" and "quiet" arguments run:

boom profile list --name Fedora --osversionid 30
OsID    Name                     OsVersion               
8896596 Fedora                   30 (Workstation Edition)

boom host create --profile 8896596 --add-opts debug --del-opts "rhgb quiet"
Created host profile with host_id ff4266a:
  Host ID: "ff4266a7a0ceac789d65df75a1edd47b832dd9c5",
  Host name: "localhost.localdomain",
  Machine ID: "653b444d513a43239c37deae4f5fe644",
  OS ID: "8896596a45fcc9e36e9c87aee77ab3e422da2635",
  Add options: "debug", Del options: "rhgb quiet",
  Name: "Fedora", Short name: "fedora", Version: "30 (Workstation Edition)",
  Version ID: "30", UTS release pattern: "fc30",
  Kernel pattern: "/vmlinuz-%{version}", Initramfs pattern: "/initramfs-%{version}.img",
  Root options (LVM2): "rd.lvm.lv=%{lvm_root_lv}",
  Root options (BTRFS): "rootflags=%{btrfs_subvolume}",
  Options: "root=%{root_device} ro %{root_opts}"

Creating a BootEntry

To create a new boot entry using an existing OsProfile, use the boom create command, specifying the OsProfile using its assigned identifier:

# boom profile list --short-name rhel
OsID    Name                            OsVersion
98c3edb Red Hat Enterprise Linux Server 6 (Server)
c0b921e Red Hat Enterprise Linux Server 7 (Server)

# boom create --profile 3fc389b --title "RHEL7 snapshot" --version 3.10-272.el7 --root-lv vg00/lvol0-snap
Created entry with boot_id a5aef11:
title RHEL7 snapshot
machine-id 611f38fd887d41dea7eb3403b2730a76
version 3.10-272.el7
linux /boot/vmlinuz-3.10-272.el7
initrd /boot/initramfs-3.10-272.el7.img
options root=/dev/vg00/lvol0-snap ro rd.lvm.lv=vg00/lvol0-snap rhgb quiet

Once the entry has been created it will appear in the boot loader menu as configured:

      Red Hat Enterprise Linux Server (3.10.0-327.el7.x86_64) 7.2 (Maipo)
      Red Hat Enterprise Linux Server (3.10.0-272.el7.x86_64) 7.2 (Maipo)
      RHEL7 Snapshot











      Use the ↑ and ↓ keys to change the selection.
      Press 'e' to edit the selected item, or 'c' for a command prompt.

If creating an entry for the currently running kernel version, and the OsProfile of the running host, these options can be omitted from the create command:

# boom create --title "Fedora 26 snapshot" --root-lv vg_hex/root-snap-f26
Created entry with boot_id d12c177:
  title Fedora 26 snapshot
  machine-id 611f38fd887d41dea7eb3403b2730a76
  version 4.13.5-200.fc26.x86_64
  linux /kernel-4.13.5-200.fc26.x86_64
  initrd /initramfs-4.13.5-200.fc26.x86_64.img
  options root=/dev/vg_hex/root-snap-f26 ro rd.lvm.lv=vg_hex/root-snap-f26

      Red Hat Enterprise Linux Server (3.10.0-327.el7.x86_64) 7.2 (Maipo)
      Red Hat Enterprise Linux Server (3.10.0-272.el7.x86_64) 7.2 (Maipo)
      Fedora 26 snapshot (4.13.5-200.fc26.x86_64)
      RHEL7 Snapshot











      Use the ↑ and ↓ keys to change the selection.
      Press 'e' to edit the selected item, or 'c' for a command prompt.

Grub2 Integration

Boom includes scripts to integrate with versions of grub2 that support the BLS extension (including the builds of Grub shipped with Fedora and Red Hat Enterprise Linux).

The scripts support optionally placing all boom-managed entries into a separate named submenu.

Submenu support

To place all boom-managed boot entries into a separate submenu edit the file /etc/default/boom and set the BOOM_USE_SUBMENU variable to yes:

BOOM_USE_SUBMENU="yes"

To change the name of the submenu modify the BOOM_SUBMENU_NAME variable:

BOOM_SUBMENU_NAME="Snapshots"

After modifying the file run the grub2-mkconfig program to update the Grub boot loader configuration.

If submenu support is enabled a new entry (named Snapshots in this example) will appear at the bottom of the main Grub2 menu:

      Red Hat Enterprise Linux Server (3.10.0-327.el7.x86_64) 7.2 (Maipo)
      Red Hat Enterprise Linux Server (3.10.0-272.el7.x86_64) 7.2 (Maipo)
      Snapshots











      Use the ↑ and ↓ keys to change the selection.
      Press 'e' to edit the selected item, or 'c' for a command prompt.

Hitting enter on the submenu item will display the available boom boot entries:

      RHEL7 Snapshot (3.10.0-327.el7.x86_64) 2017-10-10
      RHEL7 Snapshot (3.10.0-327.el7.x86_64) 2017-10-01
      RHEL7 Snapshot (3.10.0-272.el7.x86_64) 2017-09-20
      RHEL7 Snapshot (3.10.0-272.el7.x86_64) 2017-08-13
      Fedora 24 (4.11.12-100.fc24.x86_64)








      Use the ↑ and ↓ keys to change the selection.
      Press 'e' to edit the selected item, or 'c' for a command prompt.
      Press Escape to return to the previous menu.

Python API

Boom also supports programatic use via a Python API. The API is flexible and allows greater customisation than is possible using the command line tool.

Two interfaces are provided: a procedural command-driven interface that closely mimics the command line tool (the boom CLI is implemented using this interface), and a native object interface that provides complete access to boom's capabilities and full control over boom OsProfile BootEntry, and BootParams objects. User-defined tabular reports may also be created using the boom.report module.

Command API

The command API is implemented in the boom.command sub-module. Programs wishing to use the command API can just import this module:

import boom.command

The command API is documented at readthedocs.org.

Object API

The object API is implemented in several boom sub-modules:

  • boom
  • boom.bootloader
  • boom.config
  • boom.osprofile
  • boom.hostprofile
  • boom.report

Applications using the object API need only import the sub-modules that contain the needed interfaces.

The object API is documented at readthedocs.org.

Patches and pull requests

Patches can be submitted via the mailing list or as GitHub pull requests. If using GitHub please make sure your branch applies to the current master as a 'fast forward' merge (i.e. without creating a merge commit). Use the git rebase command to update your branch to the current master if necessary.

Documentation

API documentation is automatically generated using Sphinx and Read the Docs.

Installation and user documentation will be added in a future update.