Debian Bug report logs - #349674
unison: causes data loss if one of the replicas disappears

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Gabor Gombas <gombasg@sztaki.hu>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: unison: causes data loss if one of the replicas disappears

Date: Tue, 24 Jan 2006 14:35:25 +0100

Package: unison
Version: 2.13.16-4
Severity: critical
Justification: causes serious data loss


Hi,

I'm regularly replicating my home directory to an USB harddisk using
unison. This morning the USB drive got disconnected during the
synchronization (hw error). Instead of noticing that one of the replica
roots have completely disappeared and aborting, unison started to delete
large amounts of data from my home directory. Luckily I could restore
most of it, but this behaviour makes unison unsuitable as a serious
synchronization tool.

Possible solution: unison should do a stat() on the replica roots before
delete operations and if the st_dev field changes (i.e. the file system
containing the replica is unmounted or is over-mounted) it should abort
the synchronization. This is not a complete solution as it does not
protect from e.g. bind mounts, but it would at least cover the
"removable device fails causing the mount to go away" case.

Gabor

-- System Information:
Debian Release: testing/unstable
  APT prefers unstable
  APT policy: (990, 'unstable'), (500, 'testing'), (500, 'stable'), (101, 'experimental')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.15
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)

Versions of packages unison depends on:
ii  libc6                         2.3.5-12   GNU C Library: Shared libraries an

Versions of packages unison recommends:
ii  openssh-client [ssh-client]   1:4.2p1-5  Secure shell client, an rlogin/rsh

-- no debconf information

Message #10 received at 349674@bugs.debian.org (full text, mbox, reply):

From: "Sylvain Le Gall" <sylvain.le-gall@polytechnique.org>

To: Gabor Gombas <gombasg@sztaki.hu>, 349674@bugs.debian.org

Subject: Re: Bug#349674: unison: causes data loss if one of the replicas disappears

Date: Tue, 24 Jan 2006 21:44:59 +0100

Hello,

On Tue, Jan 24, 2006 at 02:35:25PM +0100, Gabor Gombas wrote:
> Package: unison
> Version: 2.13.16-4
> Severity: critical
> Justification: causes serious data loss
> 
> 
> Hi,
> 
> I'm regularly replicating my home directory to an USB harddisk using
> unison. This morning the USB drive got disconnected during the
> synchronization (hw error). Instead of noticing that one of the replica
> roots have completely disappeared and aborting, unison started to delete
> large amounts of data from my home directory. Luckily I could restore
> most of it, but this behaviour makes unison unsuitable as a serious
> synchronization tool.
> 
> Possible solution: unison should do a stat() on the replica roots before
> delete operations and if the st_dev field changes (i.e. the file system
> containing the replica is unmounted or is over-mounted) it should abort
> the synchronization. This is not a complete solution as it does not
> protect from e.g. bind mounts, but it would at least cover the
> "removable device fails causing the mount to go away" case.
> 
> Gabor
> 

Was it during the synchronisation phase (when effectively doing
operation) or before (when calculating changes) ?

I think, it is the first case, and in this case, i agree : it a real
problem.

Kind regard
Sylvain Le Gall

Message #15 received at 349674@bugs.debian.org (full text, mbox, reply):

From: Gabor Gombas <gombasg@sztaki.hu>

To: Sylvain Le Gall <sylvain.le-gall@polytechnique.org>

Cc: 349674@bugs.debian.org

Subject: Re: Bug#349674: unison: causes data loss if one of the replicas disappears

Date: Wed, 25 Jan 2006 11:43:26 +0100

On Tue, Jan 24, 2006 at 09:44:59PM +0100, Sylvain Le Gall wrote:

> Was it during the synchronisation phase (when effectively doing
> operation) or before (when calculating changes) ?

I don't really know, I was not sitting in front of the machine during
the synchronization. I only realized the end result.

> I think, it is the first case, and in this case, i agree : it a real
> problem.

I think not noticing that the whole filesystem has changed is a problem
in any phase.

Gabor

-- 
     ---------------------------------------------------------
     MTA SZTAKI Computer and Automation Research Institute
                Hungarian Academy of Sciences,
     Laboratory of Parallel and Distributed Systems
     Address   : H-1132 Budapest Victor Hugo u. 18-22. Hungary
     Phone/Fax : +36 1 329-78-64 (secretary)
     W3        : http://www.lpds.sztaki.hu
     ---------------------------------------------------------

Message #20 received at 349674@bugs.debian.org (full text, mbox, reply):

From: Kapil Hari Paranjape <kapil@imsc.res.in>

To: 349674@bugs.debian.org, Benjamin Pierce <bcpierce@cis.upenn.edu>

Cc: control@bugs.debian.org

Subject: Unison and removable drives

Date: Mon, 31 Jul 2006 09:30:35 +0530

[Message part 1 (text/plain, inline)]

tags 349674 upstream
thanks

Hello,

As reported in Debian bug #349674 which can be seen at

	http://bugs.debian.org/349674

Unison has problems when the file system is removed from under it.

For example, here is the result of my experiment.

	Setup: A USB drive is mounted at /media/fakehd0 
	       /media/fakehd0/a and /tmp/b are directories
	       that have already been synchronised by unison
	       in the past.

	Experiment:
	       Run the command 
	          unison -batch -logfile /tmp/test.log /media/fakehd0/a /tmp/b
	       and unplug the USB drive from the machine before the
	       synchronisation can complete.

	Result:
	       The files on /tmp/b that were not synchronised before
	       the unplugging are deleted.

	       In the logfile we see that there is an I/O error
	       recorded by unison before this problem occurs.

	Real World Scenario:
	       USB and floppy media are known to fail "mysteriously"
	       while they are being used. A problem like that above
	       could lead to a "backup" procedure deleting files
	       instead of backing them up!

	Possible solution:
	       unison should abort on I/O errors.

Thanks and regards,

Kapil.
-- 

[signature.asc (application/pgp-signature, inline)]

Message #27 received at 349674@bugs.debian.org (full text, mbox, reply):

From: "Sylvain Le Gall" <sylvain.le-gall@polytechnique.org>

To: Kapil Hari Paranjape <kapil@imsc.res.in>, 349674@bugs.debian.org

Subject: Re: Bug#349674: Unison and removable drives

Date: Fri, 4 Aug 2006 01:05:45 +0200

Hello,

On Mon, Jul 31, 2006 at 09:30:35AM +0530, Kapil Hari Paranjape wrote:
> tags 349674 upstream
> thanks
> 
> Hello,
> 
> As reported in Debian bug #349674 which can be seen at
> 
> 	http://bugs.debian.org/349674
> 
> Unison has problems when the file system is removed from under it.
> 
> For example, here is the result of my experiment.
> 
> 	Setup: A USB drive is mounted at /media/fakehd0 
> 	       /media/fakehd0/a and /tmp/b are directories
> 	       that have already been synchronised by unison
> 	       in the past.
> 
> 	Experiment:
> 	       Run the command 
> 	          unison -batch -logfile /tmp/test.log /media/fakehd0/a /tmp/b
> 	       and unplug the USB drive from the machine before the
> 	       synchronisation can complete.
> 
> 	Result:
> 	       The files on /tmp/b that were not synchronised before
> 	       the unplugging are deleted.
> 
> 	       In the logfile we see that there is an I/O error
> 	       recorded by unison before this problem occurs.
> 
> 	Real World Scenario:
> 	       USB and floppy media are known to fail "mysteriously"
> 	       while they are being used. A problem like that above
> 	       could lead to a "backup" procedure deleting files
> 	       instead of backing them up!
> 
> 	Possible solution:
> 	       unison should abort on I/O errors.
> 
> Thanks and regards,
> 

I see, you submitted the bug directly upstream... very well and thanks.

I hope it will be fixed in the next upstream release (but i think i will
backport changes to the current unison package).

Kind regard
Sylvain Le Gall

Message #32 received at 349674@bugs.debian.org (full text, mbox, reply):

From: Reuben Thomas <rrt@sc3d.org>

To: 349674@bugs.debian.org

Subject: Could the severity of this bug be reduced to allow unison into testing?

Date: Thu, 19 Oct 2006 08:38:47 +0100 (BST)

Rationale: this is a bug in all current versions of unison. It applies 
to a specific use case, one in which one of the media is likely to 
disappear during backup. By all means add a big fat warning until the 
bug is fixed, but please don't prevent us getting the up-to-date 
version of unison.

The version currently in testing, 2.9.1, is built with hacks, has UI 
problems as a result (I filed a bug which was reasonably closed wontfix 
about this) and has bugs and missing features compared to the current 
version; hence, allowing the current version into testing is an 
improvement all round.

-- 
http://rrt.sc3d.org/ | It is impossible to love and be wise (Francis Bacon)

Message #37 received at 349674@bugs.debian.org (full text, mbox, reply):

From: Sylvain Le Gall <gildor@debian.org>

To: Reuben Thomas <rrt@sc3d.org>, 349674@bugs.debian.org

Subject: Re: Bug#349674: Could the severity of this bug be reduced to allow unison into testing?

Date: Thu, 19 Oct 2006 15:14:05 +0200

severity 349674 important 

thanks 

Hello,

On Thu, Oct 19, 2006 at 08:38:47AM +0100, Reuben Thomas wrote:
> Rationale: this is a bug in all current versions of unison. It applies 
> to a specific use case, one in which one of the media is likely to 
> disappear during backup. By all means add a big fat warning until the 
> bug is fixed, but please don't prevent us getting the up-to-date 
> version of unison.
> 
> The version currently in testing, 2.9.1, is built with hacks, has UI 
> problems as a result (I filed a bug which was reasonably closed wontfix 
> about this) and has bugs and missing features compared to the current 
> version; hence, allowing the current version into testing is an 
> improvement all round.
> 

A comprehensive user :-)

OK, i agree with the severity lowering. I will apply the correction that
the upstream proposed to me : explain in README.Debian that using unison
on removable media in batch mode is unsafe (it is enough specific to
lower the bug severity).

FYI, i will begin to work on a correction of this ASAP (ie when i will
have made my other package enter etch with a decent version number).

Kind regard
Sylvain Le Gall

Message #44 received at 349674@bugs.debian.org (full text, mbox, reply):

From: Gabor Gombas <gombasg@sztaki.hu>

To: Benjamin Pierce <bcpierce@cis.upenn.edu>

Cc: Kapil Hari Paranjape <kapil@imsc.res.in>, sylvain.le-gall@polytechnique.org, unison-users@yahoogroups.com, 349674@bugs.debian.org

Subject: Re: [unison-users] Problem with Unison and removable drives

Date: Tue, 13 Feb 2007 16:09:40 +0100

Hi,

The same bug happened again with unison 2.13.16-5 (Debian Sid): USB
drive holding one of the replicas suddenly went offline during sync,
that caused a lot of I/O errors in the kernel log and HAL unmounted the
drive, which in turn caused unison to wipe half of my home directory
(the other replica) before I noticed and interrupted it. The
$HOME/.unison directory where the sync log was kept was also deleted so
I have no idea at what stage of the sync did the USB disconnect happen.

Note to Debian: README.Debian _still_ does not contain any warnings that
unison is not safe to use on removable media.

Gabor

-- 
     ---------------------------------------------------------
     MTA SZTAKI Computer and Automation Research Institute
                Hungarian Academy of Sciences
     ---------------------------------------------------------

Message #49 received at 349674@bugs.debian.org (full text, mbox, reply):

From: sylvain@le-gall.net

To: Gabor Gombas <gombasg@sztaki.hu>

Cc: Benjamin Pierce <bcpierce@cis.upenn.edu>, Kapil Hari Paranjape <kapil@imsc.res.in>, sylvain.le-gall@polytechnique.org, unison-users@yahoogroups.com, 349674@bugs.debian.org

Subject: Re: [unison-users] Problem with Unison and removable drives

Date: Tue, 13 Feb 2007 17:20:29 +0100

Hello, 

Gabor Gombas writes: 

> Hi, 
> 
> The same bug happened again with unison 2.13.16-5 (Debian Sid): USB
> drive holding one of the replicas suddenly went offline during sync,
> that caused a lot of I/O errors in the kernel log and HAL unmounted the
> drive, which in turn caused unison to wipe half of my home directory
> (the other replica) before I noticed and interrupted it. The
> $HOME/.unison directory where the sync log was kept was also deleted so
> I have no idea at what stage of the sync did the USB disconnect happen. 
> 
> Note to Debian: README.Debian _still_ does not contain any warnings that
> unison is not safe to use on removable media. 
> 

I have a lot of real life work -- and i was in need to fix all other
debian packages for the freeze. 

I will include this note and do an upload -- just for you -- tonight. 

FYI, debian package stable version of unison. Unison-hackers has done
some works on this issue in the development branch of unison. This is
the reason why this bug is not fixed in the debian version. 

Since, i think a lot of unison bugs are corrected in development version i
think i will split again the package in :
* unison: development version
* unison2.13.16: stable version
* unison2.9.1: compatibility with debian stable 

In other word, unison package will follow development version of unison ! 

Kind regard
Sylvain Le Gall 

Message #54 received at 349674@bugs.debian.org (full text, mbox, reply):

From: Reuben Thomas <rrt@sc3d.org>

To: Debian Bug Tracking System <349674@bugs.debian.org>

Subject: unison-gtk: This bug is fixed upstream

Date: Thu, 16 Aug 2007 21:16:40 +0100

Package: unison-gtk
Version: 2.13.16-6
Followup-For: Bug #349674

The changelog for 2.27.29 says this bug was fixed some time after
2.17. There is currently no post-2.17 stable release, so this is for
information only, but at least it means the bug has been fixed.

-- System Information:
Debian Release: lenny/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)

Kernel: Linux 2.6.21-2-686 (SMP w/1 CPU core)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages unison-gtk depends on:
ii  libatk1.0-0                   1.18.0-2   The ATK accessibility toolkit
ii  libc6                         2.6-2      GNU C Library: Shared libraries
ii  libcairo2                     1.4.10-1   The Cairo 2D vector graphics libra
ii  libfontconfig1                2.4.2-1.2  generic font configuration library
ii  libglib2.0-0                  2.12.13-1  The GLib library of C routines
ii  libgtk2.0-0                   2.10.13-1  The GTK+ graphical user interface 
ii  libpango1.0-0                 1.16.5-1   Layout and rendering of internatio
ii  libx11-6                      2:1.0.3-7  X11 client-side library
ii  libxcursor1                   1:1.1.8-2  X cursor management library
ii  libxext6                      1:1.0.3-2  X11 miscellaneous extension librar
ii  libxfixes3                    1:4.0.3-2  X11 miscellaneous 'fixes' extensio
ii  libxi6                        2:1.1.2-1  X11 Input extension library
ii  libxinerama1                  1:1.0.2-1  X11 Xinerama extension library
ii  libxrandr2                    2:1.2.1-1  X11 RandR extension library
ii  libxrender1                   1:0.9.2-1  X Rendering Extension client libra

Versions of packages unison-gtk recommends:
ii  openssh-client [ssh-client]   1:4.6p1-5  secure shell client, an rlogin/rsh
pn  ssh-askpass                   <none>     (no description available)

-- no debconf information

Message #59 received at 349674@bugs.debian.org (full text, mbox, reply):

From: Sylvain Le Gall <gildor@debian.org>

To: Reuben Thomas <rrt@sc3d.org>, 349674@bugs.debian.org

Subject: Re: Bug#349674: unison-gtk: This bug is fixed upstream

Date: Thu, 16 Aug 2007 22:50:17 +0200

On Thu, Aug 16, 2007 at 09:16:40PM +0100, Reuben Thomas wrote:
> Package: unison-gtk
> Version: 2.13.16-6
> Followup-For: Bug #349674
> 
> The changelog for 2.27.29 says this bug was fixed some time after
> 2.17. There is currently no post-2.17 stable release, so this is for
> information only, but at least it means the bug has been fixed.

Great, waiting for a new stable release

Regards
Sylvain Le Gall

Message #66 received at 349674-close@bugs.debian.org (full text, mbox, reply):

From: Sylvain Le Gall <gildor@debian.org>

To: 349674-close@bugs.debian.org

Subject: Bug#349674: fixed in unison 2.27.57-1

Date: Fri, 18 Apr 2008 10:32:03 +0000

Source: unison
Source-Version: 2.27.57-1

We believe that the bug you reported is fixed in the latest version of
unison, which is due to be installed in the Debian FTP archive:

unison-gtk_2.27.57-1_amd64.deb
  to pool/main/u/unison/unison-gtk_2.27.57-1_amd64.deb
unison_2.27.57-1.diff.gz
  to pool/main/u/unison/unison_2.27.57-1.diff.gz
unison_2.27.57-1.dsc
  to pool/main/u/unison/unison_2.27.57-1.dsc
unison_2.27.57-1_amd64.deb
  to pool/main/u/unison/unison_2.27.57-1_amd64.deb
unison_2.27.57.orig.tar.gz
  to pool/main/u/unison/unison_2.27.57.orig.tar.gz



A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 349674@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Sylvain Le Gall <gildor@debian.org> (supplier of updated unison package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@debian.org)


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Format: 1.8
Date: Mon, 14 Apr 2008 19:39:39 +0200
Source: unison
Binary: unison unison-gtk
Architecture: source amd64
Version: 2.27.57-1
Distribution: unstable
Urgency: low
Maintainer: Sylvain Le Gall <gildor@debian.org>
Changed-By: Sylvain Le Gall <gildor@debian.org>
Description: 
 unison     - A file-synchronization tool for Unix and Windows
 unison-gtk - A file-synchronization tool for Unix and Windows with GTK+ interf
Closes: 349674 462598 476051
Changes: 
 unison (2.27.57-1) unstable; urgency=low
 .
   [ Sylvain Le Gall]
   * New upstream release (Closes: #462598):
     * New option mountpoint can help avoid problem with removable media
       (Closes: #349674)
   * Unset CFLAGS in debian/rules (Closes: #476051)
   * Upgrade to standards version 3.7.3 (no change)
   * Update README.Debian to add new package unison2.13.16
   * Remove debian/control.in
   * Remove now useless gtkfont patch
   * Change doc-base section to File Management
 .
   [ Stefano Zacchiroli ]
   * promote Homepage to a real debian/control field, now that dpkg supports it
   * fix vcs-svn field to point just above the debian/ dir
Checksums-Sha1: 
 8a38c2b4d772f18051fd175a380ad7b74b238c20 1308 unison_2.27.57-1.dsc
 9892680d8bd3e3c50031451cc6e77eb5431768ea 617253 unison_2.27.57.orig.tar.gz
 7b3a66e9d5d34a822f1d6c46d235088abf1a0cf7 14562 unison_2.27.57-1.diff.gz
 18db98f8381ddb0afb55819c49a35f62f4f2a9cc 565016 unison_2.27.57-1_amd64.deb
 db442981096049f300919a1ad6869e2081ec0d12 972904 unison-gtk_2.27.57-1_amd64.deb
Checksums-Sha256: 
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 49299ec14216a8467b2c6ba148f8145bec31fa787433f9ce3851c2d62f0035ae 617253 unison_2.27.57.orig.tar.gz
 32383df582f7b489b42393e89633d43a35ad44c5eae8eb6589824ea1d3bb0f46 14562 unison_2.27.57-1.diff.gz
 7cc13e255a0c51666a6417dca038f1e6abc1475b3d689d7b5c61d9e80384da20 565016 unison_2.27.57-1_amd64.deb
 63949f7a400c031840b7d626ffc2b34a7473576a8559f843561cd18a725f96ab 972904 unison-gtk_2.27.57-1_amd64.deb
Files: 
 df2f42eded3c678dc1726f42c30b6274 1308 utils optional unison_2.27.57-1.dsc
 4ba0a3e4bf4b4ad0c063f86391371f78 617253 utils optional unison_2.27.57.orig.tar.gz
 6a2c040e3b88e249a1ad644c17c8c16d 14562 utils optional unison_2.27.57-1.diff.gz
 b621e0d0b10e4645d2f6d0dcf39c8e93 565016 utils optional unison_2.27.57-1_amd64.deb
 15460dadef20fa865ef25fa2f33c3fdc 972904 utils optional unison-gtk_2.27.57-1_amd64.deb

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