pro[zind]

Extend a ZFS root pool after Ubuntu installation

dans Bloc-notes  | Traductions : fr

Since Eoan Ermine (Ubuntu 19.10), Ubuntu installer (for desktop) can use ZFS as root file-system.

The current LTS, Focal Fossa (Ubuntu 20.04) provides only a mono-disk installation, here's how to enhance a mono-disk installation into a mirrored-disk installation to use data resilience provided by ZFS.

🚧 ZFS on root is still experimental 🚧

🔧 Howto

  • sda is the disk used by installer
  • sdb is the disk we're going to add to create a mirror
user@focal:~$ lsblk -a
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931,5G  0 disk
├─sda1   8:1    0   513M  0 part
├─sda2   8:2    0     1K  0 part
├─sda5   8:5    0     2G  0 part [SWAP]
├─sda6   8:6    0     2G  0 part
└─sda7   8:7    0   927G  0 part
sdb      8:16   0 931,5G  0 disk

user@focal:~$ blkid
/dev/sda1: UUID="BFE4-2413" TYPE="vfat" PARTUUID="f0771fca-01"
/dev/sda5: UUID="42456868-afc5-4dea-8b73-11257b84890e" TYPE="swap" PARTUUID="f0771fca-05"
/dev/sda6: LABEL="bpool" UUID="11578277722432725130" UUID_SUB="9520999198366150859" TYPE="zfs_member" PARTUUID="f0771fca-06"
/dev/sda7: LABEL="rpool" UUID="13693210375688435814" UUID_SUB="8709443765040685487" TYPE="zfs_member" PARTUUID="f0771fca-07"

Ubuntu creates 2 pools :

  1. bpool : containing boot pool
  2. rpool : containing root pool, with all file-system
user@focal:~$ zpool list
NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
bpool  1,88G  91,2M  1,79G        -         -     0%     4%  1.00x    ONLINE  -
rpool   920G  3,19G   917G        -         -     0%     0%  1.00x    ONLINE  -

user@focal:~$ zpool status
  pool: bpool
 state: ONLINE
  scan: none requested
config:

    NAME           STATE     READ WRITE CKSUM
    bpool          ONLINE       0     0     0
      f0771fca-06  ONLINE       0     0     0

errors: No known data errors

  pool: rpool
 state: ONLINE
  scan: none requested
config:

    NAME           STATE     READ WRITE CKSUM
    rpool          ONLINE       0     0     0
      f0771fca-07  ONLINE       0     0     0

Run fdisk to copy sda partition table to sdb using sfdisk compatible script files (see manpage).

user@focal:~$ fdisk /dev/sda #copy to file with O
user@focal:~$ fdisk /dev/sdb #import from file with I

user@focal:~$ lsblk -a
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931,5G  0 disk
├─sda1   8:1    0   513M  0 part
├─sda2   8:2    0     1K  0 part
├─sda5   8:5    0     2G  0 part [SWAP]
├─sda6   8:6    0     2G  0 part
└─sda7   8:7    0   927G  0 part
sdb      8:16   0 931,5G  0 disk
├─sdb1   8:17   0   513M  0 part
├─sdb2   8:18   0     1K  0 part
├─sdb5   8:21   0     2G  0 part
├─sdb6   8:22   0     2G  0 part
└─sdb7   8:23   0   927G  0 part

Attach the twin partitions on pools :

user@focal:~$ sudo zpool attach bpool f0771fca-06 /dev/sdb6
user@focal:~$ sudo zpool attach rpool f0771fca-07 /dev/sdb7

🎉 Tada!

user@focal:~$ zpool status
  pool: bpool
 state: ONLINE
  scan: resilvered 92,2M in 0 days 00:00:01 with 0 errors on Sun Jan  3 22:22:09 2021
config:

    NAME             STATE     READ WRITE CKSUM
    bpool            ONLINE       0     0     0
      mirror-0       ONLINE       0     0     0
        f0771fca-06  ONLINE       0     0     0
        sdb6         ONLINE       0     0     0

errors: No known data errors

  pool: rpool
 state: ONLINE
  scan: resilvered 4,05G in 0 days 00:01:06 with 0 errors on Sun Jan  3 22:24:05 2021
remove: Removal of vdev 1 copied 3,36M in 0h0m, completed on Sun Jan  3 21:14:16 2021
    456 memory used for removed device mappings
config:

    NAME             STATE     READ WRITE CKSUM
    rpool            ONLINE       0     0     0
      mirror-0       ONLINE       0     0     0
        f0771fca-07  ONLINE       0     0     0
        sdb7         ONLINE       0     0     0

errors: No known data errors

📝 30/4/2021 edit

  1. Steps compatible with version 21.04 «Hirsute Hippo» instaler;
    • the partition numbering seems to be continuous now
  2. Enlarge swap with the available partition on the added disk
user@hirsute:~$ free -h
              total       utilisé      libre     partagé tamp/cache   disponible
Mem:           11Gi       974Mi        10Gi       7,0Mi       259Mi        10Gi
Swap:          2,0Gi      0B           2,0Gi

user@hirsute:~$ sudo mkswap /dev/sdb5
Configure l'espace d'échange (swap) en version 1, taille = 2 GiB (2147479552 octets)
pas d'étiquette, UUID=bbbbbbbb-bbbbb-bbbb-bbbb-bbbbbbb

user@hirsute:~$ grep swap /etc/fstab
UUID=aaaaaaaa-aaaaa-aaaa-aaaa-aaaaaaa   none    swap    sw  0   0
UUID=bbbbbbbb-bbbbb-bbbb-bbbb-bbbbbbb   none    swap    sw  0   0

user@hirsute:~$ sudo swapon -U bbbbbbbb-bbbbb-bbbb-bbbb-bbbbbbb

user@hirsute:~$ free -h
              total       utilisé      libre     partagé tamp/cache   disponible
Mem:           11Gi       1,0Gi        10Gi       7,0Mi       261Mi        10Gi
Swap:          4,0Gi      0B           4,0Gi

🔖 References

  1. ZFS Features and Terminology - www.freebsd.org
  2. The Z File System (ZFS) - www.freebsd.org
  3. OpenZFS - github.com
  4. Enhancing our ZFS support on Ubuntu 19.10 – an introduction - ubuntu.com
  5. ZFS focus on Ubuntu 20.04 LTS: what’s new? - ubuntu.com
  6. zpool manpage - manpages.ubuntu.com
  7. zfs manpage - manpages.ubuntu.com