"borg delete --cache-only" does not work as expected

[agrommek]

Have you checked borgbackup docs, FAQ, and open GitHub issues?

Yes

Is this a BUG / ISSUE report or a QUESTION?

Bug

System information. For client/server mode post info for both machines.

Your borg version (borg -V).

borg-2.0.0b5

Operating system (distribution) and version.

Arch Linux, Ubuntu Server 22.04

Hardware / network configuration, and filesystems used.

Local Borg repositories for testing, ext4

How much data is handled by borg?

A few GB, for testing

Full borg commandline that lead to the problem (leave away excludes and passwords)

$  borg-2.0.0b5-linuxnew64 delete --repo /path/to/testrepo1  --cache-only --verbose
Enter passphrase for key /mnt/HDD/scratch/testrepos/testrepo1: 
Aborting: if you really want to delete all archives, please use -a 'sh:*' or just delete the whole repository (might be much faster).

Describe the problem you're observing.

Expected behavior:
From the docs and from the name of the switch I would expect that borg would clean the cache, i.e. delete the files cache and/or delete the chunks cache and/or delete the contents of chunks.archives.d. It should not delete or modify stored archives.

Observed behavior:
Borg refuses to run when no --match-archives switch is also given. There is different behavior, depending on the value of this parameter:

1. --cache-only --match-archives 'id:some-not-existing archive': nothing gets deleted (as the archive does not exist), cache files have same size as before. No deletion of cache.
2. --cache-only --match-archives 'id:some-existing archive': archive gets deleted, cache files have same size as before. No deletion of cache.
3. --cache-only --match-archives 'sh:*: repo is empty afterwards, chunks cache is small (empty?), files cache remains.

In my opinion this is a bug, as it violates the "principle of least surprise". If an option switch says "cache-only", then it should operate only on the cache. On the other hand, if this switch is supposed to somehow only delete the cache for the archives specified with --match-archives, then this behavior should be documented much more extensively.

[ThomasWaldmann]

Hmm, that sounds weird. Maybe something got broken due to the misc other changes in borg2. I'll have a look.

[ThomasWaldmann]

2 issues here:

• one should use borg rdelete --cache-ony as this is a repo-level (not archive-level) operation.
• borg erroneously accepts borg delete --cache-only, that is a bug.

[ThomasWaldmann]

Fixed by #7455.