Impossible to create a full backup due to permission error on /home/lost+found folder

[JonathanMM]

Error only happen since upgrade to 20.10. Everything worked on ubuntu 20.04. Same error if I try to change location of the backup. Folder /home/lost+found/ is not in the configuration of deja-dup.

Error message displayed:
  File "/usr/bin/duplicity", line 92, in with_tempdir
    fn()
  File "/usr/lib/python3/dist-packages/duplicity/dup_main.py", line 1538, in main
    do_backup(action)
  File "/usr/lib/python3/dist-packages/duplicity/dup_main.py", line 1662, in do_backup
    full_backup(col_stats)
  File "/usr/lib/python3/dist-packages/duplicity/dup_main.py", line 559, in full_backup
    bytes_written = dummy_backup(tarblock_iter)
  File "/usr/lib/python3/dist-packages/duplicity/dup_main.py", line 224, in dummy_backup
    while next(tarblock_iter):
  File "/usr/lib/python3/dist-packages/duplicity/diffdir.py", line 544, in __next__
    result = self.process(next(self.input_iter)) # pylint: disable=assignment-from-no-return
  File "/usr/lib/python3/dist-packages/duplicity/diffdir.py", line 209, in get_delta_iter
    for new_path, sig_path in collated:
  File "/usr/lib/python3/dist-packages/duplicity/diffdir.py", line 310, in collate2iters
    for relem1 in riter1:
  File "/usr/lib/python3/dist-packages/duplicity/selection.py", line 97, in __next__
    return next(self.iter)
  File "/usr/lib/python3/dist-packages/duplicity/selection.py", line 181, in Iterate
    subpath, val = next(diryield_stack[-1])
  File "/usr/lib/python3/dist-packages/duplicity/selection.py", line 148, in diryield
    s = self.Select(new_path)
  File "/usr/lib/python3/dist-packages/duplicity/selection.py", line 210, in Select
    result = sf(path)
  File "/usr/lib/python3/dist-packages/duplicity/selection.py", line 458, in exclude_sel_func
    elif path.append(filename).exists():
  File "/usr/lib/python3/dist-packages/duplicity/path.py", line 566, in append
    return self.__class__(self.base, self.index + (ext,))
  File "/usr/lib/python3/dist-packages/duplicity/path.py", line 539, in __init__
    self.setdata()
  File "/usr/lib/python3/dist-packages/duplicity/path.py", line 549, in setdata
    self.stat = os.lstat(self.name)
 PermissionError: [Errno 13] Permission denied: b'/home/lost+found/.deja-dup-ignore'

[Michael Terry (mterry)]

This is a bug in a possible interaction between Deja Dup >= 42.1 and Duplicity < 0.8.16.

Which means as of this writing it definitely affects 20.10, and may affect 21.04 if Duplicity doesn't get bumped before release.

This was fixed in Duplicity by the following patch: https://gitlab.com/duplicity/duplicity/-/commit/f6809e8a4e09b70138a0902434d8c88d3c4c8ccb

[Michael Terry (mterry)]

Oh and I should have mentioned workarounds:
- give everyone execute permission on the offending folder
- install the snap version of duplicity
- install the snap (or flatpak) version of deja-dup

[Michael Terry (mterry)]

(Any one of those should work by itself)

[Sebastien Bacher (seb128)]

Thanks for the comment Michael, we will make sure it's fixed this cycle. Unsure if the case if common enough to justify a SRU to a non LTS serie yet though

[Anthony Berent (anthony-berent)]

Probably not unexpected, but I am seeing this problem if any folder within my home folder doesn't have execute permission, not just lost+found

[Sebastien Bacher (seb128)]

The fix is in this update https://launchpad.net/ubuntu/+source/duplicity/0.8.17-1