--link-dest doesn't work if target file exists (but needs updating)
Kevin Korb
kmk at sanitarium.net
Fri Jan 20 15:42:43 MST 2012
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Am I understanding right that your source and your link-dest are
actually the same path? If so what are you trying to do that wouldn't
be accomplished with a simple 'cp -l'?
Also, when using --link-dest the target is treated differently.
Normally the target is an empty directory but if files already exist
the behavior you are seeing is what is supposed to happen. Instead of
deleting files and replacing them with links it assumes that they are
already linked to whatever they are supposed to be linked to and
updates them accordingly.
On 01/20/12 17:27, Brian J. Murrell wrote:
> Using:
>
> # rsync --version rsync version 3.0.7 protocol version 30
> Copyright (C) 1996-2009 by Andrew Tridgell, Wayne Davison, and
> others. Web site: http://rsync.samba.org/ Capabilities: 64-bit
> files, 64-bit inums, 32-bit timestamps, 64-bit long ints,
> socketpairs, hardlinks, symlinks, IPv6, batchfiles, inplace,
> append, ACLs, xattrs, iconv, symtimes
>
> rsync comes with ABSOLUTELY NO WARRANTY. This is free software,
> and you are welcome to redistribute it under certain conditions.
> See the GNU General Public Licence for details.
>
> Given two files:
>
> # /bin/ls -li {source,dest}/var/lib/mysql/mythconverg/jobqueue.MYD
> 44695517 -rw-rw---- 2 sshd messagebus 5492 2012-01-19 00:31
> source/var/lib/mysql/mythconverg/jobqueue.MYD 49676928 -rw-rw---- 1
> sshd messagebus 5492 2012-01-18 12:00
> dest/var/lib/mysql/mythconverg/jobqueue.MYD
>
> Their md5sums:
>
> # md5sum {source,dest}/var/lib/mysql/mythconverg/jobqueue.MYD
> b87dafdcf59ab3e7e9907c15385175b3
> source/var/lib/mysql/mythconverg/jobqueue.MYD
> c03b1ee584ef1405958b695f4e55b51d
> dest/var/lib/mysql/mythconverg/jobqueue.MYD
>
> Let's try to create a link from
> source/var/lib/mysql/mythconverg/jobqueue.MYD to
> dest/var/lib/mysql/mythconverg/jobqueue.MYD
>
> Dry-run first to see what rsync tells us it's going to do:
>
> # rsync -naiiAXH --link-dest=/source/var/lib/mysql/mythconverg/
> source/var/lib/mysql/mythconverg/jobqueue.MYD
> dest/var/lib/mysql/mythconverg/
>> f..t...... jobqueue.MYD
>
> Looks like it's not going to create a link. Let's be sure:
>
> # rsync -aiiAXH --link-dest=/source/var/lib/mysql/mythconverg/
> source/var/lib/mysql/mythconverg/jobqueue.MYD
> dest/var/lib/mysql/mythconverg/
>> f..t...... jobqueue.MYD
>
> Yup, looks like it didn't create a link. The proof:
>
> # /bin/ls -li {source,dest}/var/lib/mysql/mythconverg/jobqueue.MYD
> 44695517 -rw-rw---- 2 sshd messagebus 5492 2012-01-19 00:31
> source/var/lib/mysql/mythconverg/jobqueue.MYD 49676897 -rw-rw---- 1
> sshd messagebus 5492 2012-01-19 00:31
> dest/var/lib/mysql/mythconverg/jobqueue.MYD
>
> Yet it did copy the file:
>
> # md5sum {source,dest}/var/lib/mysql/mythconverg/jobqueue.MYD
> b87dafdcf59ab3e7e9907c15385175b3
> source/var/lib/mysql/mythconverg/jobqueue.MYD
> b87dafdcf59ab3e7e9907c15385175b3
> dest/var/lib/mysql/mythconverg/jobqueue.MYD
>
> Why didn't it remove the existing file and create the link like we
> wanted it to with --link-dest? Let's try another file just to
> prove that it will create a link if the destination file doesn't
> exist:
>
> Two different files, same use case though:
>
> # /bin/ls -li {source,dest}/var/lib/mysql/mythconverg/jobqueue.MYI
> 44695518 -rw-rw---- 2 sshd messagebus 5120 2012-01-19 00:31
> source/var/lib/mysql/mythconverg/jobqueue.MYI 49676956 -rw-rw---- 1
> sshd messagebus 5120 2012-01-18 12:00
> dest/var/lib/mysql/mythconverg/jobqueue.MYI
>
> Different content again:
>
> # md5sum {source,dest}/var/lib/mysql/mythconverg/jobqueue.MYI
> 6a0b5bdedfe738fbca17630e6496f85c
> dest/var/lib/mysql/mythconverg/jobqueue.MYI
> 9052f8e598f8ee3bdcb2cbc510f0564c
> source/var/lib/mysql/mythconverg/jobqueue.MYI
>
> See what rsync says it's going to do (before we remove the target
> file):
>
> # rsync -naiiAXH --link-dest=/source/var/lib/mysql/mythconverg/
> source/var/lib/mysql/mythconverg/jobqueue.MYI
> dest/var/lib/mysql/mythconverg/
>> f..t...... jobqueue.MYI
>
> Again, it's going to copy.
>
> But if we remove the target file and see what rsync says it's going
> to do:
>
> # rm dest/var/lib/mysql/mythconverg/jobqueue.MYI # rsync -naiiAXH
> --link-dest=/source/var/lib/mysql/mythconverg/
> source/var/lib/mysql/mythconverg/jobqueue.MYI
> dest/var/dest/var/lib/mysql/mythconverg/ hf jobqueue.MYI
>
> Ah ha! Say's it's going to link. Let's actually do it and see:
>
> # rsync -aiiAXH --link-dest=/source/var/lib/mysql/mythconverg/
> source/var/lib/mysql/mythconverg/jobqueue.MYI
> dest/var/lib/mysql/mythconverg/ hf jobqueue.MYI
>
> And sure enough, we now have three links to the same file (as we
> would expect):
>
> # /bin/ls -li {source,dest}/var/lib/mysql/mythconverg/jobqueue.MYI
> 44695518 -rw-rw---- 3 sshd messagebus 5120 2012-01-19 00:31
> source/var/lib/mysql/mythconverg/jobqueue.MYI 44695518 -rw-rw---- 3
> sshd messagebus 5120 2012-01-19 00:31
> dest/var/lib/mysql/mythconverg/jobqueue.MYI
>
> And the content (although we know it should report the same):
>
> # md5sum {source,dest}/var/lib/mysql/mythconverg/jobqueue.MYI
> 9052f8e598f8ee3bdcb2cbc510f0564c
> dest/var/lib/mysql/mythconverg/jobqueue.MYI
> 9052f8e598f8ee3bdcb2cbc510f0564c
> source/var/lib/mysql/mythconverg/jobqueue.MYI
>
> So why doesn't the same thing work when the destination file
> exists? The element of least surprise would make me think it
> should. That is, even if the destination file exists, if the
> result of the sync is the same as a file that a --link-dest points
> to, it should remove the destination file and create the link.
>
> Thoughts?
>
> b.
>
>
>
>
>
>
- --
~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~
Kevin Korb Phone: (407) 252-6853
Systems Administrator Internet:
FutureQuest, Inc. Kevin at FutureQuest.net (work)
Orlando, Florida kmk at sanitarium.net (personal)
Web page: http://www.sanitarium.net/
PGP public key available on web site.
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