services.zfs.autoScrub.enable renders system unbootable

[pbogdan]

Issue description

System hangs during boot when the timer configured via services.zfs.autoScrub.enable fires during the boot sequence.

Steps to reproduce

1. Enable services.zfs.autoScrub.enable option.
2. Configure services.zfs.autoScrub.interval option such that the timer will be due to run immediately upon the next reboot of the system.
3. nixos-rebuild boot
4. Shutdown; allow sufficient amount of time to pass. Boot the system, observe the system to hang during the boot sequence.

Technical details

• system: "x86_64-linux"
• host os: Linux 4.19.13, NixOS, 19.03.git.d1fff1e (Koi)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.1.3
• channels(pbogdan): ""
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

[lheckemann]

Does setting systemd.timer.zfs-scrub.after = ["multi-user.target"]; help?

[pbogdan]

s/timer/timers but otherwise yes, it does help, thank you.

[mlen]

Hi,

I reproduced this on 19.03 yesterday. The unit already contained After=multi-user.target, so it seems it is not sufficient to fix this. Some data about my system:

$ nixos-version 
19.03.172883.1601f559e89 (Koi)
$ uname -a
Linux crow 4.19.50 #1-NixOS SMP Tue Jun 11 10:20:57 UTC 2019 x86_64 GNU/Linux
$ readlink $(which zfs)
/nix/store/q4jv6p15j4mh2d9slahhak2b2znbfix4-zfs-user-0.7.13/bin/zfs