Hi there,
On Sat, 18 Jul 2026, Ron Colcernian wrote:
Would someone kindly point me to the remedy for the following message?
What document should I read to guide me to resolution of this issue?
I have 1157 of these messages.
2026-07-16 01:24:05 admin : BackupPC_refCountUpdate: missing pool
file 2f168f994f2744a2c4c9046b821ebcc1 count 1
I don't know how long this has been happening, sadly.
Cpool is V4 (90% of it was converted from V3, 10% is newly created V4
daily backups)
Running backuppc, version 4.4.0
Ubuntu 24.04 Instance on a Proxmo install.
Going through this a bit quickly because of time pressures, I'm sorry
if there are things like typos and repetition which I've seen in some
of my recent posts. :( Also I've generalized it a little - I tend to
do that in case it helps other people later on; I guess you have just
one missing pool file?
CAUSES:
Unfortunately there seem to be several causes for missing pool files.
They are mentioned in mailng list threads listed below - the mailing
list archive is a valuable resource. I prefer to download the entire
archive and use 'grep' to search it.
Here are the causes that I know of, descending order of probability:
1. When either the BackupPC server or one of its clients is shut down
improperly while a backup is active.
2. Problems when migrating from a V3 pool to a V4 pool. Possibly the
system 'ulimit' may have been too small, but the migration utility has
not been tested well. In view of the numbers of installations and how
often the utility is used, it probably never will be. My experience
with it was unsatisfactory but that was around ten years ago. In the
end for that installation I started from scratch with a fresh V4 taken
from source (the copy which gave trouble was from a Debian package).
3. Some older versions of BackupPC 4.x contained faults that sometimes
caused missing pool files. At least to the extent that they are known
those faults have been fixed. Obviously upgrade faulty versions, but
version 4.4.0 should be fine. There are discussions in Github issues
as well as on the mailing list.
FIXES:
Fortunately, missing pool files isn't a show-stopper. If you come
across missing pool file messages:
If they're artifacts of the V3->V4 conversion, then you can probably
just ignore them. The messages will eventually stop when the backups
that reference them expire. If you delete those backups manually the
same thing will happen (but you don't know which they are, read on).
You can just tell BackupPC to back up the files which are missing from
the pool. It isn't straightforward to get from a pool file hash to
the original file but there are useful pointers in the mail archives.
Below [*] are some threads from the mailing list with more info. Some
are a little old, but no less useful for that. Some refer to scripts
that you might find useful. I see there's a promise of another script
in the not too distant future from Matthias@gmx... (and I'd be pleased
to see it Matthias, whatever state it's in. :)
If you're using rsync/d for Xfer it might be worth tweaking the rsync
options so that the destination files are compared bytewise instead of
relying on the comparison of the metadata (timestamps and file sizes).
I haven't tried this, and don't know for sure that it will help - I'm
going on the comment in the config.pl file. The tweak I'm thinking of
is --ignore-times in place of --checksum in $Conf{RsyncFullArgsExtra}.
You could instead add this to $Conf{RsyncArgsExtra} so that it would
affect incremental backups as well as fulls, but that might not help
much because the file missing from the pool probably isn't changing on
the client (or it would have been backed up by now anyway) so it won't
be compared until the next full backup happens.
You might well find that all the missing pool files relate to a single
client. In that case you might just rename the client directory in
/var/lib/Backuppc/pc/[**] to some random string which doesn't resemble
one of your host names. BackupPC will start backups from scratch for
that client. I do that a lot in testing. When you're happy that your
backups are OK, just delete the renamed directory tree.
HTH
[*]
https://sourceforge.net/p/backuppc/mailman/message/35708181/
https://sourceforge.net/p/backuppc/mailman/message/37269343/
https://sourceforge.net/p/backuppc/mailman/message/58833484/
https://sourceforge.net/p/backuppc/mailman/message/59127801/
https://sourceforge.net/p/backuppc/mailman/message/59221642/
[**]
Or wherever your /pc/ and /pool/ directories happen to live.
--
73,
Ged.
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