AssertionError when mounting archive

[MaxKerney]

While using Pika Backup, I encountered an error when trying to mount an archive to browse. I raised an issue on the Pika Backup repo (Issue 672), but the conclusion was that it was an issue with borg (I get the same issue using another GUI, Vorta). Below is the error message I get when running the CLI borg commands directly:

max@fedora:~$ sudo dnf install borgbackup
[sudo] password for max: 
Updating and loading repositories:
Repositories loaded.
Package "borgbackup-1.4.4-1.fc43.x86_64" is already installed.

max@fedora:~$ borg mount -o 'umask=0000,uid=1000' '/run/media/max/Backup-B/Backup-B' '/run/user/1000/pika-backup/mount/d6af7df0'
Enter passphrase for key /run/media/max/Backup-B/Backup-B: 
Local Exception
Traceback (most recent call last):
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 5759, in main
    exit_code = archiver.run(args)
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 5677, in run
    rc = func(args)
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 1454, in do_mount
    self._do_mount(args)
    ~~~~~~~~~~~~~~^^^^^^
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 200, in wrapper
    return method(self, args, repository=repository, **kwargs)
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 1464, in _do_mount
    operations.mount(args.mountpoint, args.options, args.foreground, args.show_rc)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.14/site-packages/borg/fuse.py", line 564, in mount
    assert isinstance(dir_group, str)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^
AssertionError

Platform: Linux fedora 6.19.11-200.fc43.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Apr  2 16:55:52 UTC 2026 x86_64
Linux: Unknown Linux  
Borg: 1.4.4  Python: CPython 3.14.3 msgpack: 1.1.0 fuse: llfuse 1.5.2 [pyfuse3,llfuse]
PID: 11136  CWD: /home/max
sys.argv: ['/usr/bin/borg', 'mount', '-o', 'umask=0000,uid=1000', '/run/media/max/Backup-B/Backup-B', '/run/user/1000/pika-backup/mount/d6af7df0']
SSH_ORIGINAL_COMMAND: None

max@fedora:~$ borg mount /run/media/max/Backup-B/Backup-B /run/user/1000/pika-backup/mount/d6af7df0
Enter passphrase for key /run/media/max/Backup-B/Backup-B: 
Local Exception
Traceback (most recent call last):
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 5759, in main
    exit_code = archiver.run(args)
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 5677, in run
    rc = func(args)
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 1454, in do_mount
    self._do_mount(args)
    ~~~~~~~~~~~~~~^^^^^^
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 200, in wrapper
    return method(self, args, repository=repository, **kwargs)
  File "/usr/lib64/python3.14/site-packages/borg/archiver.py", line 1464, in _do_mount
    operations.mount(args.mountpoint, args.options, args.foreground, args.show_rc)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.14/site-packages/borg/fuse.py", line 564, in mount
    assert isinstance(dir_group, str)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^
AssertionError

Platform: Linux fedora 6.19.11-200.fc43.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Apr  2 16:55:52 UTC 2026 x86_64
Linux: Unknown Linux  
Borg: 1.4.4  Python: CPython 3.14.3 msgpack: 1.1.0 fuse: llfuse 1.5.2 [pyfuse3,llfuse]
PID: 11147  CWD: /home/max
sys.argv: ['/usr/bin/borg', 'mount', '/run/media/max/Backup-B/Backup-B', '/run/user/1000/pika-backup/mount/d6af7df0']
SSH_ORIGINAL_COMMAND: None

Fuse is installed, in case that's relevant:

max@fedora:~$ dnf list --installed | grep -i "fuse"
fuse.x86_64                                          2.9.9-24.fc43                       0e44b8838a064239bd0106e9c9253add
fuse-common.x86_64                                   3.16.2-6.fc43                       <unknown>
fuse-libs.x86_64                                     2.9.9-24.fc43                       fedora
fuse-overlayfs.x86_64                                1.13-4.fc43                         0e44b8838a064239bd0106e9c9253add
fuse3.x86_64                                         3.16.2-6.fc43                       <unknown>
fuse3-libs.x86_64                                    3.16.2-6.fc43                       <unknown>
glusterfs-fuse.x86_64                                11.2-4.fc43                         0e44b8838a064239bd0106e9c9253add
gvfs-fuse.x86_64                                     1.58.4-1.fc43                       <unknown>
python3-llfuse.x86_64                                1.5.2-1.fc43                        <unknown>

Please let me know if you need any more information.

[ThomasWaldmann]

Is there a user with uid 1000 in /etc/passwd?

[MaxKerney]

Yes, it looks like there is: max:x:1000:1000:Max Kerney:/home/max:/bin/bash.

[sophie-h]

Isn't the relevant question if there is a 1000 group in /etc/group because the group assertion fails?

Also note that the issue contains output with -o 'umask=0000,uid=1000' and without that specified if that's relevant.

[ThomasWaldmann]

@sophie-h You are completely right!

@MaxKerney ^^^

Hmm, maybe either don't give uid= when running the mount command as the desired user.

Or, give both consistent uid and gid when mounting as root.

[MaxKerney]

Ah. It doesn't look like there is a 1000 group in /etc/group. I may have accidentally deleted it while trying to set up a plugdev group to get OpenRazer working for my mouse. Could you tell me how I should go about adding it back?

[MaxKerney]

It's ok, I've figured it out. And that has fixed the issue! Thanks for your help, and sorry to have wasted your time!

[ThomasWaldmann]

Reopening:

Improve the code to suggest to the user to check whether the given uid / gid actually can be resolved to a username / groupname.