proc-sys-fs-binfmt_misc.mount

[tomberek]

I've noticed this on my own deployments and in other comments and dicsussions #465 and #391.

proc-sys-fs-binfmt_misc.mount [failed]

A manual restart clears the error.

[greglearns]

+1 still exists

[andrewchambers]

getting this in my virtual box tests.

[kolloch]

It might be detected incorrectly as an error. It also happens on my machine that I have not setup with nixos:

$ systemctl status proc-sys-fs-binfmt_misc.mount
● proc-sys-fs-binfmt_misc.mount - Arbitrary Executable File Formats File System
   Loaded: loaded (/nix/store/vb5k2bvs7ralcnpw4kxwf9qmsmqq4xri-systemd-234/example/systemd/system/proc-sys-fs-binfmt_misc.mount; linked; vendor preset: enabled)
   Active: inactive (dead)
    Where: /proc/sys/fs/binfmt_misc
     What: binfmt_misc
     Docs: https://www.kernel.org/doc/html/latest/admin-guide/binfmt-misc.html
           https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems

Furthermore, on all the affected machines I see the following mount, so it seems to have an effect (or something else):

systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,...)

That said, other mount units look different:

# systemctl status sys-kernel-debug.mount
● sys-kernel-debug.mount - Kernel Debug File System
   Loaded: loaded (/nix/store/vb5k2bvs7ralcnpw4kxwf9qmsmqq4xri-systemd-234/example/systemd/system/sys-kernel-debug.mount; enabled; vendor preset: enab
   Active: active (mounted) since Wed 2018-01-24 20:47:22 UTC; 1 weeks 1 days ago
    Where: /sys/kernel/debug
     What: debugfs
     Docs: https://www.kernel.org/doc/Documentation/filesystems/debugfs.txt
           https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
    Tasks: 0 (limit: 4915)
   CGroup: /system.slice/sys-kernel-debug.mount

Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

[kolloch]

Aaah, I understood a bit more about this. There is an accompanying proc-sys-fs-binfmt_misc.automount unit which cause the mount I mention before. If you execute cd /proc/sys/fs/binfmt_misc/, the automount is activated and the systemd unit becomes "active":

● proc-sys-fs-binfmt_misc.mount - Arbitrary Executable File Formats File System
   Loaded: loaded (/nix/store/vb5k2bvs7ralcnpw4kxwf9qmsmqq4xri-systemd-234/example/systemd/system/proc-sys-fs-binfmt_misc.mount; linked; vendor preset: enabled)
   Active: active (mounted) since Fri 2018-02-02 07:32:36 UTC; 2min 12s ago
    Where: /proc/sys/fs/binfmt_misc
     What: binfmt_misc
     Docs: https://www.kernel.org/doc/html/latest/admin-guide/binfmt-misc.html
           https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
  Process: 1483 ExecMount=/nix/store/yizg9cg4x6xbyhz4h2w9qklql85m5xkx-util-linux-2.31-bin/bin/mount binfmt_misc /proc/sys/fs/binfmt_misc -t binfmt_misc (code=exited, status=0/SUCCESS)
    Tasks: 0 (limit: 4915)
   CGroup: /system.slice/proc-sys-fs-binfmt_misc.mount

Feb 02 07:32:36 webserver systemd[1]: Mounting Arbitrary Executable File Formats File System...
Feb 02 07:32:36 webserver systemd[1]: Mounted Arbitrary Executable File Formats File System.

[devhell]

So, this doesn't look like it's affecting anything negatively, it is rather annoying though to see that in nixops check outputs. Is there a sensible solution to this?

[tomberek]

@devhell This removes the error, but it's not very satisfying, not sure what the right solution is:

  boot.binfmtMiscRegistrations = {
    dummy = {
      mask = "00000";
      recognitionType = "magic";
      magicOrExtension = "never";
      interpreter = /bin/sh;
    };
  };

[matthewbauer]

I think you can avoid that altogether with this:

systemd.additionalUpstreamSystemUnits =
      [ "proc-sys-fs-binfmt_misc.automount"
        "proc-sys-fs-binfmt_misc.mount"
      ];

This looks like a fairly common systemd error. Might be worthwhile to open an issue there.

[kirelagin]

The weird thing is that # systemctl list-units | grep binfmt returns nothing for me and systemctl status is all green with:

    State: running
     Jobs: 0 queued
   Failed: 0 units

so why does nixops report this unit as failed if it doesn’t even exist?

[kirelagin]

Ohhh ok, so nixops does this:

# systemctl --all | grep not-found
● proc-sys-fs-binfmt_misc.automount                                           not-found inactive dead      proc-sys-fs-binfmt_misc.automount
● proc-sys-fs-binfmt_misc.mount                                               not-found inactive dead      proc-sys-fs-binfmt_misc.mount
● tmp.mount                                                                   not-found inactive dead      tmp.mount
● auditd.service                                                              not-found inactive dead      auditd.service
● display-manager.service                                                     not-found inactive dead      display-manager.service
● emergency.service                                                           not-found inactive dead      emergency.service
● plymouth-start.service                                                      not-found inactive dead      plymouth-start.service
● syslog.service                                                              not-found inactive dead      syslog.service
● systemd-hwdb-update.service                                                 not-found inactive dead      systemd-hwdb-update.service
● systemd-sysusers.service                                                    not-found inactive dead      systemd-sysusers.service
● cryptsetup.target                                                           not-found inactive dead      cryptsetup.target
● emergency.target                                                            not-found inactive dead      emergency.target
● initrd-switch-root.target                                                   not-found inactive dead      initrd-switch-root.target

Then ignores everything which is not a .mount and then filters out everything in /tmp, in /sys, or in /dev, but our patient is in /proc/sys. Should we just add an exception for /proc or /proc/sys?

[lordcirth]

Filtering out /proc here seems reasonable to me. Can anyone think of a case where that would be undesirable?

[datafoo]

May be related to: NixOS/nixpkgs#87687

[flokli]

possible fix: NixOS/nixpkgs#87742

[flokli]

@grahamc with NixOS/nixpkgs#87742 closed, can you close this too?

[adisbladis]

Fixed in nixpkgs, closing!

[Xe]

This is still happening for me