Downgrading or upgrading unison to avoid compatibility issue

[larienna]

I have a server computer which has unison 2.40 installed on jessie while having my new computer installed on debian 9 with unison 2.48 and both computers cannot communicate with each other.

So I searched a bit and thought of downgrading my unison on my main computer to 2.40. So I uninstalled unison, and downloaded and installed the following package

unison2.32.52_2.32.52-7_amd64.deb
unison_2.40.102-2_amd64.deb
unison-all_2.40+2_all.deb

But I still get the error message that the expected version was 2.40, but 2.48 was sent.

So I was wondering if there is a way to upgrade the server computer on Jessie to 2.48 instead and reinstall the client computer to 2.48.

If possible, how can I upgrade my server to 2.48?
else, what went wrong with my downgrade explained above?

[debiman]

just to get things straight, your computers CAN communicate with each other, it's just unison that doesn't like version mismatches.
i ran into the same problem at some point and to my knowledge there's just nothing to do about it.
except, a workaround exists: mount the remote server via sshfs or nfs, then perform a local unison sync (i.e. unison doesn't have to be installed at all on the server).

[kedaha]

Hi,
unison is currently at the same version in current stable, testing and sid: 2.48.3-1 so if you wish to try, it can be easily backported on your jessie server (don't do it on stretch!), following the method given at SimpleBackportCreation.
Just make a directory for building the package and kick off with:

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$ dget -x http://http.debian.net/debian/pool/main/u/unison/unison_2.48.3-1.dsc 

and proceed as detailed on the wiki.

[stevepusser]

Unison 2.48.3 from Stretch didn't seem to have any trouble backporting to Jessie or even Wheezy:

https://build.opensuse.org/package/show ... sie/unison

the 64-bit Jessie debs end up here: http://download.opensuse.org/repositori ... 8.0/amd64/

[larienna]

I was not exactly sure if it was possible to backport the package. I'll give it a try.

Yes, it's just unison that complains about versions.

[kedaha]

I was not exactly sure if it was possible to backport the package. I'll give it a try.

Yes, it's just unison that complains about versions.

You can either attempt to backport it yourself or install it from stevepusser's repository.
I haven't set up an unofficial repository myself but I know it can be successfully backported because I did it myself in Debian 8 "jessie."

[larienna]

I tried following the steps on the SimpleBackportCreation page for package unison and unison-all. I don't need unison-gtk because it's only a server.

Even if I have little clue about what I was doing, I successfully built "unison-all", but I could not build "unison". The unison package failed at step:

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dpkg-buildpackage -us -uc

With the following error message

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dpkg-source -b unison-2.48.3
dpkg-source: info: using source format `3.0 (quilt)'
dpkg-source: info: building unison using existing ./unison_2.48.3.orig.tar.gz
dpkg-source: warning: ignoring deletion of file lwt/depend, use --include-removal to override
dpkg-source: warning: ignoring deletion of file ubase/depend, use --include-removal to override
dpkg-source: error: cannot represent change to fsmonitor/watchercommon.o: binary file contents changed
dpkg-source: error: add fsmonitor/watchercommon.o in debian/source/include-binaries if you want to store the modified binary in the debian tarball
dpkg-source: error: unrepresentable changes to source
dpkg-buildpackage: error: dpkg-source -b unison-2.48.3 gave error exit status 2

I'll try to continue the procedure for unison-all. Not sure if the server is located in unison-all or unison.

[larienna]

I forgot to note that there is a file named:

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unison_2.48.3-1_i386.deb

that has been created. So I am not sure if it's installable if the step above failed.

Unison all cannot be installed because it requires unison main package. So I am stuck there. At worst I can try to install the package above.

[larienna]

OK, I gave it a try and installed both packages. Then ran unison from my client computer and it worked. Thanks for the help.

[kedaha]

Yes, the backport method is a useful addition to ones bag of tricks; it's good that you did it yourself and it worked. One can always look at at the error messages some time.