Preface

I made a mistake and installed Ubuntu 20.04 LTS with an encrypted ZFS / OpenZFS root partition on my productive working desktop in a dual boot configuration (see partition table below). But I didn't pay proper attention on the tutorial I was following and now it seems that I have a Swap partition of 4G although I have 32G of RAM (EDIT: I found out how I'm able to increase the Swap but I still can't go into hibernation — see below). Therefore I cannot put this machine on hibernation.

What's the best way to solve this issue, so that I can put this machine into hibernation?

Current state

$ sudo fdisk -l /dev/nvme0n1
Disk /dev/nvme0n1: 1.88 TiB, 2048408248320 bytes, 4000797360 sectors
Disk model: KXG60PNV2T04 NVMe KIOXIA 2048GB         
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 1FCA11ED-9263-4C06-A8DF-594C0DE84AFA

Device             Start        End    Sectors   Size Type
/dev/nvme0n1p1      2048    1085439    1083392   529M Windows recovery environment
/dev/nvme0n1p2   1085440    1290239     204800   100M EFI System
/dev/nvme0n1p3   1290240    1323007      32768    16M Microsoft reserved
/dev/nvme0n1p4   1323008  409420488  408097481 194.6G Microsoft basic data
/dev/nvme0n1p5 409421824  410920959    1499136   732M Windows recovery environment
/dev/nvme0n1p6 410923008  415117311    4194304     2G Linux filesystem
/dev/nvme0n1p7 415117312 4000797326 3585680015   1.7T Linux filesystem

$ sudo swapon --show --output all
NAME     TYPE      SIZE USED PRIO UUID                                 LABEL
/dev/zd0 partition   4G   0B   -2 1e1fb013-69d9-4878-b358-6b8ee53d5b09

$ sudo zpool list -v
NAME          SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
Root         1.66T   535G  1.13T        -         -     2%    31%  1.00x    ONLINE  -
  nvme0n1p7  1.66T   535G  1.13T        -         -     2%  31.5%      -  ONLINE

$ sudo zpool status -v
  pool: Root
 state: ONLINE
  scan: none requested
config:

    NAME         STATE     READ WRITE CKSUM
    Root         ONLINE       0     0     0
      nvme0n1p7  ONLINE       0     0     0

errors: No known data errors

$ sudo zfs list
NAME                                                                              USED  AVAIL     REFER  MOUNTPOINT
Root                                                                              539G  1.08T      192K  none
Root/root                                                                         534G  1.08T      530G  /
Root/root/00a891589b00cebc55cb6767e266ca38ac201daf3a6048c1f33d7d55c0710533        544K  1.08T      143M  legacy
[…] # many other legacy mount points
Root/root/ffe52d35c873e6a417ee12c7025d848dac1f269b8078266f00a8d8088fd34384        396K  1.08T      607M  legacy
Root/swap                                                                        4.25G  1.08T      172M  -

$ sudo zfs get all Root/swap
NAME       PROPERTY              VALUE                 SOURCE
Root/swap  type                  volume                -
Root/swap  creation              So Aug  2 15:36 2020  -
Root/swap  used                  4.25G                 -
Root/swap  available             1.08T                 -
Root/swap  referenced            172M                  -
Root/swap  compressratio         1.00x                 -
Root/swap  reservation           none                  default
Root/swap  volsize               4G                    local
Root/swap  volblocksize          4K                    -
Root/swap  checksum              on                    default
Root/swap  compression           off                   local
Root/swap  readonly              off                   default
Root/swap  createtxg             3746                  -
Root/swap  copies                1                     default
Root/swap  refreservation        4.25G                 local
Root/swap  guid                  12379969387189982956  -
Root/swap  primarycache          metadata              local
Root/swap  secondarycache        none                  local
Root/swap  usedbysnapshots       0B                    -
Root/swap  usedbydataset         172M                  -
Root/swap  usedbychildren        0B                    -
Root/swap  usedbyrefreservation  4.08G                 -
Root/swap  logbias               throughput            local
Root/swap  objsetid              278                   -
Root/swap  dedup                 off                   default
Root/swap  mlslabel              none                  default
Root/swap  sync                  always                local
Root/swap  refcompressratio      1.00x                 -
Root/swap  written               172M                  -
Root/swap  logicalused           169M                  -
Root/swap  logicalreferenced     169M                  -
Root/swap  volmode               default               default
Root/swap  snapshot_limit        none                  default
Root/swap  snapshot_count        none                  default
Root/swap  snapdev               hidden                default
Root/swap  context               none                  default
Root/swap  fscontext             none                  default
Root/swap  defcontext            none                  default
Root/swap  rootcontext           none                  default
Root/swap  redundant_metadata    all                   default
Root/swap  encryption            aes-256-gcm           -
Root/swap  keylocation           none                  default
Root/swap  keyformat             passphrase            -
Root/swap  pbkdf2iters           342K                  -
Root/swap  encryptionroot        Root                  -
Root/swap  keystatus             available             -

What I tried

Creating a Swapfile

I thought a swapfile might be an easy fix but I was obviously wrong:

$ sudo dd if=/dev/zero of=/swapfile bs=1MiB count=$((32*1024))
32768+0 records in
32768+0 records out
34359738368 bytes (34 GB, 32 GiB) copied, 14.5783 s, 2.4 GB/s

$ sudo chmod 600 /swapfile

$ sudo swapon /swapfile
swapon: /swapfile: skipping - it appears to have holes.

So I guess I should rather increase the swap partition. It's also not clear to me why swapon claims that the swap partition has 4G although zfs get all Root/swap says that 1.08T are available.

Anything with GParted

GParted won't recognize much. This could be related to the bug in os-prober (GParted issue 14, Debian bug 888114, os-prober issue 1848496, openzfs issues 9801 and 9069)

Replacing the small Swap partition (=increasing the Swap partition on ZFS)

The creation command was inspired by a comment on GitHub but you should keep in mind not to use -o sync=always.

$ sudo zfs create -V 32G -b $(getconf PAGESIZE) -o logbias=throughput -o primarycache=metadata -o secondarycache=none -o com.sun:auto-snapshot=false -o compression=zle Root/swap_two
$ sudo zfs rename Root/swap Root/swap_bak
$ sudo zfs rename Root/swap_two Root/swap
$ sudo mkswap -f /dev/zvol/Root/swap
$ sudo swapon /dev/zvol/Root/swap

ensuring that this entry is in /etc/fstab:

/dev/zvol/Root/swap none swap discard 0 0

then reboot and remove the tiny legacy swap:

$ sudo zfs destroy Root/swap_bak

While this seem to have worked, I still cannot hibernate:

$ sudo systemctl hibernate
Failed to hibernate system via logind: Sleep verb "hibernate" not supported

Therefore I'm still open for any advice. Maybe it needs a dedicated resume parameter in GRUB_CMDLINE_LINUX_DEFAULT?

In the end the reason wasn't related to ZFS. Even after resizing the swap it didn't work because it is simply disabled on newer Ubuntu versions (it will be reconsidered though).

To solve this, you have to activate hibernation.

1. Open com.ubuntu.desktop.pkla in an editor:

$ sudo vim /var/lib/polkit-1/localauthority/10-vendor.d/com.ubuntu.desktop.pkla
# or on some machines
$ sudo vim /etc/polkit-1/localauthority/10-vendor.d/com.ubuntu.desktop.pkla

Search for the entries Disable hibernate by default in upower and Disable hibernate by default in logind and change each ResultActive value to yes.

Reboot and test the result with

$ sudo systemctl hibernate
# or
$ sudo pm-hibernate

If it still doesn't work, you might have to deactivate things like Fast boot and Secure boot in your BIOS (ATTENTION: it is very likely that you have to do that on newer machines).

If the test doesn't result in an error anymore, you should also be able to assign Hibernations to certain actions in Ubuntu settings. For instance on pressing the power button.