Does boom support multi-volume snapshots?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Boom

Issue

  • Does boom entry support snapshot for multiple logical volumes?
  • We use separate filesystems for /, /var, /tmp, /var/log, /var/crash, /var/log/audit, /home, etc. When we take a snapshot before patching or another risky activity, we take snapshots of all of these LVs. It would be great to be able to use boom to add a boot entry for snapshots is a situation like above.
  • Can we take boom snapshots of /var if /var is not under root and then later rollback if needed?

Resolution

Red Hat Enterprise Linux 7-8
At this moment this feature is not part of RHEL 7/8

Red Hat Enterprise Linux 9.4
The feature to create boom entry with multiple snapshot is introduced in boom-boot-1.6.0-2.el9 package released in errata update RHBA-2024:2291.

Root Cause

  • There was a limitation in older version of boom package which prevented the use of multi-volume snapshots.
    This feature is added in RHEL 9.4 provided boom-boot-1.6.0-2.el9 package.

Diagnostic Steps

With RHEL 9.4 provided boom package, below steps could be used to setup snapshots for different LVs in root vg and create boom entry for them:

  • e.g. for a system with separate /var and /home LVs, create snapshots of rhel/root, rhel/var, and rhel/home:

    [root@localhost ~]# lvcreate -s -n root-snap -L 1g rhel/root
  Logical volume "root-snap" created.
[root@localhost ~]# lvcreate -s -n var-snap -L 1g rhel/var
  Logical volume "var-snap" created.
[root@localhost ~]# lvcreate -s -n home-snap -L 1g rhel/home
  Logical volume "home-snap" created.

  • Set up an OsProfile and create a boom boot entry for the snapshot volumes:

    [root@localhost ~]# boom profile create --from-host
Created profile with os_id d5bded8:
  OS ID: "d5bded84c4f37fc29568e83ea2cb2b1dfc3d5789",
  Name: "Red Hat Enterprise Linux", Short name: "rhel",
  Version: "9.4 (Plow)", Version ID: "9.4",
  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} crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/swap rhgb quiet",
  Title: "%{os_name} %{os_version_id} (%{version})",
  Optional keys: "grub_users grub_arg grub_class id", UTS release pattern: "el9"

[root@localhost ~]# boom create --title Snapshot --root-lv rhel/root-snap --no-fstab --mount /dev/rhel/var-snap:/var:xfs:defaults --mount /dev/rhel/home-snap:/home:xfs:defaults
Created entry with boot_id 75aa619:
  title Snapshot
  machine-id a76538d60c5a4566912a3649744f2529
  version 5.14.0-427.13.1.el9_4.x86_64
  linux /vmlinuz-5.14.0-427.13.1.el9_4.x86_64
  initrd /initramfs-5.14.0-427.13.1.el9_4.x86_64.img
  options root=/dev/rhel/root-snap ro rd.lvm.lv=rhel/root-snap crashkernel=1G-4G:192M,4G-64G:256M,64G-:512M resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/swap rhgb quiet fstab=no systemd.mount-extra=/dev/rhel/var-snap:/var:xfs:defaults systemd.mount-extra=/dev/rhel/home-snap:/home:xfs:defaults
  grub_users $grub_users
  grub_arg --unrestricted
  grub_class kernel

  • Reboot and select Snapshot from the Grub2 menu. With updated boom packages, the system successfully boots into the snapshot environment:

    # grep rhel /proc/mounts 
/dev/mapper/rhel-root--snap / xfs rw,seclabel,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota 0 0
/dev/mapper/rhel-var--snap /var xfs rw,seclabel,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota 0 0
/dev/mapper/rhel-home--snap /home xfs rw,seclabel,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota 0 0


[root@localhost ~]# systemctl status -- -.mount
● -.mount - Root Mount
     Loaded: loaded
     Active: active (mounted)
      Where: /
       What: /dev/mapper/rhel-root--snap
[root@localhost ~]# systemctl status var.mount
● var.mount - /var
     Loaded: loaded (/proc/cmdline; generated)
     Active: active (mounted) since Mon 2024-02-26 19:53:44 GMT; 12min ago
      Until: Mon 2024-02-26 19:53:44 GMT; 12min ago
      Where: /var
       What: /dev/mapper/rhel-var--snap
       Docs: man:fstab(5)
             man:systemd-fstab-generator(8)
      Tasks: 0 (limit: 7739)
     Memory: 4.0K
        CPU: 16ms
     CGroup: /system.slice/var.mount

Feb 26 19:53:44 localhost systemd[1]: Mounting /var...
Feb 26 19:53:44 localhost systemd[1]: Mounted /var.


[root@localhost ~]# systemctl status home.mount
● home.mount - /home
     Loaded: loaded (/proc/cmdline; generated)
     Active: active (mounted) since Mon 2024-02-26 19:53:44 GMT; 12min ago
      Until: Mon 2024-02-26 19:53:44 GMT; 12min ago
      Where: /home
       What: /dev/mapper/rhel-home--snap
       Docs: man:fstab(5)
             man:systemd-fstab-generator(8)
      Tasks: 0 (limit: 7739)
     Memory: 4.0K
        CPU: 16ms
     CGroup: /system.slice/home.mount

Feb 26 19:53:44 localhost systemd[1]: Mounting /home...
Feb 26 19:53:44 localhost systemd[1]: Mounted /home.

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