Package: unison
Version: 2.48.3-1
Severity: important
Short summary:
In various settings unison reports files as changing/changed even
though they are/were untouched. This happens mainly for large (> 100
MB) files and is in reproducible as it continues to occur, but some
files might go "fine" in one run and then are reported problematic in
another. This problem is amplified in local settings (i.e. source and
target are on the same machine), but occurs (less frequently) also
over slow links (DSL upload).
Long story:
I'm using unison for ages (I started before 2005) and it was a very
reliable tool. The main use case is a backup onto an external (USB
bound) RAID array, which is only connected during backup time. This
worked without a hitch until my previous machine died last year.
I got a new machine and since the backup was full (and the disks not
large enough to match the disks of the new machine) I also bought new
disks for the RAID array (the housing/driver itself remained
unchanged).
Using a self built 4.5 and a self built 4.8 kernel, the symptoms
mentioned above occur, simmilarly with the official Debian kernel
which I just installed for testing. I'm not 100% sure where the
error lies, but since I also upgraded from stable to testing (using
a new, unfortunately incompatible usison where possible) I assume
it to be the culprit.
The RAID drive at one time contained some errors, but I corrected them
and fsck (using -c) did not find any further problems (it needed a run
with -D).
Since living without a (reliable) backup I set up a secondary backup
onto a remote computer (connected via DSL, i.e. using a slow uplink).
Here the error occurs much less frequent, but still. I use unison to
"upload" a large (tar.xz) file without problems and if I rerun then
suddenly "the file has changed during synchronization".
All files tested so far lay on a local SSD, it's the first time I have
an SSD, so maybe an interaction of unison and the kernel with an SSD
involved triggers the problem?
I'm willing run tests, create logs/dumps as necessary and also try
(kernel) patches if/where necessary to track this down.
Please do not hesitate to ask for any information you might need to
track this down. On other machines with (older) unisons I've not
experienced this problems, but there I seldomly have/had such large
files and no SSD neither.
-- System Information:
Debian Release: stretch/sid
APT prefers testing
APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 4.8.0-2-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to de_DE.UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages unison depends on:
ii libc6 2.24-8
Versions of packages unison recommends:
ii openssh-client [ssh-client] 1:7.3p1-5
Versions of packages unison suggests:
ii unison-all 2.48+2
-- no debconf information
--
Dr. Helge Kreutzmann debian@helgefjell.de
Dipl.-Phys. http://www.helgefjell.de/debian.php
64bit GNU powered gpg signed mail preferred
Help keep free software "libre": http://www.ffii.de/
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