/etc/hostid is not set after installing zfs

[Antti Toivonen]

When installing zfs on Ubuntu 16.04, official wiki instructs you to

 sudo apt install zfs

zfs points to zfsutils-linux. /etc/hostid remains missing after installation. It will cause issues, when importing zfs pool after restart.

Oct 4 07:07:13 ****** kernel: [25947.708287] SPL: The /etc/hostid file is not found.
Oct 4 07:07:13 ****** kernel: [25947.708292] SPL: using hostid 0x00000000

/etc/hostid is generated by package spl, on which zfsutils-linux should depend on. Alternatively /etc/hostid should be generated by zfsutils-linux.

/var/log$ uname -a
Linux ***** 4.4.0-31-generic #50-Ubuntu SMP Wed Jul 13 00:07:12 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

/var/log$ lsb_release -rd
Description: Ubuntu 16.04.1 LTS
Release: 16.04

/var/log$ apt show zfsutils-linux
Package: zfsutils-linux
Version: 0.6.5.6-0ubuntu12
Priority: extra
Section: admin
Source: zfs-linux
Origin: Ubuntu
Maintainer: Ubuntu Developers <email address hidden>
Original-Maintainer: Darik Horn <email address hidden>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 794 kB
Provides: zfs
Depends: init-system-helpers (>= 1.18~), zfs-doc (= 0.6.5.6-0ubuntu12), libblkid1 (>= 2.16), libc6 (>= 2.14), libnvpair1linux, libuuid1 (>= 2.16), libuutil1linux, libzfs2linux, libzpool2linux, python
Recommends: zfs-dkms, zfs-zed
Suggests: samba-common-bin (>= 3.0.23), nfs-kernel-server, zfs-initramfs
Conflicts: zfs, zfs-fuse
Replaces: zfs
Homepage: https://github.com/zfsonlinux/zfs/releases/tag/zfs-0.6.5.6
Supported: 5y
Download-Size: 276 kB
APT-Manual-Installed: yes
APT-Sources: http://fi.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
Description: Native OpenZFS management utilities for Linux
 This package provides the zpool and zfs commands that are used to
 manage OpenZFS filesystems.

[Richard Laager (rlaager)]

This isn't a huge problem. The decision to not depend on spl was intentional, to avoid dragging spl into main.

There's been some discussion on pkg-zfsonlinux-devel about how to handle hostid in Debian, which will likely be inherited by Ubuntu. If Debian's solution lands in spl instead of zfsutils-linux, then Ubuntu will have to duplicate it to zfsutils-linux to keep spl out of main.