Linux Format forums

gmport · Joined: Fri Jan 20, 2012 3:16 pm Posts: 9

Hi,

I've been using Unison for about 2 years on my installation. This comprised, an HP 6730s laptop and desktop machine, both running Ubuntu 10.04. I synchronise the laptop to the desktop, it's been running perfectly for the whole of that time.

Last week I upgraded both machines to Mint 12 using Gnome 3 with all shell extensions off. Unfortunately, I don't seem to be able to get Unison to connect to the desktop.

On the desktop, I installed SSH with:
“sudo aptitude install openssh-server unison”,

Edited sshd_config:
“PermitRootLogin” from “yes” to “no”.
added line “AllowUser gm”.
Then restarted ssh.

On the laptop, I installed Unison with:
“sudo aptitude install unison unison-gtk”.

I then set-up a profile to test it:
root = /home/gm/Documents
root = ssh://gm@mint-desktop//home/gm/Documents

This is virtually identical to what I've been using on Ubuntu for the last 2 years, apart from the desktop name.

For some reason I can't get this to work, I've been working on it for some time now. Am I missing something? Is there something different about Mint 12? Are there some other settings to be made to sshd_config?

The message I get every time is: “Fatal error, Lost connection with the server”. However, it does work if I try to sync to a local folder. This seems to indicate a problem on the desktop.

Can someone suggest a way of diagnosing the problem?

My mind's not so good these days as I'm getting on a bit, so if someone could possibly advise me I'd be very grateful. I'm running out of ideas.

Regards
gmport

Dutch_Master · LXF regular Joined: Tue Mar 27, 2007 2:49 am Posts: 2353

You assign 'root' twice: first as local, then as a remote directory. This may cause confusion. Perhaps I'm wrong, as I have no knowledge of Unison Razz

gmport · Joined: Fri Jan 20, 2012 3:16 pm Posts: 9

Thanks for your reply Dutch_Master,

Two roots are necessary in unison, as you say: one local and one remote.

Regards
gmport

Bruno · Posted: Fri Jan 20, 2012 6:04 pm Post subject:

Hi gmport,

Just looking at your second, remote root: I think it should read:

nelz · Posted: Fri Jan 20, 2012 10:44 pm Post subject:

The first thing to check is whether you can connect to the remote computer with SSH. The lost connection error could be caused by an SSH login failure.

If that's not the problem, look in ~/unison.log for more clues.
_________________
Unix is user-friendly. It's just very selective about who it's friends are.

gmport · Joined: Fri Jan 20, 2012 3:16 pm Posts: 9

Thank you for your replies Bruno and Nelz,

I have tried your suggestion Bruno, unfortunately without success. I just get the same error message “Fatal error – Lost contact with server”.

However, I went to the Unison site at: http://www.cis.upenn.edu/~bcpierce/unison/download/releases/stable/unison-manual.html

and found a manual, It's for version 2.40.61 and I'm using 2.32.52, so I hope it's still relevant. The manual has instructions for testing the connection by typing: "ssh remotehostname unison -version" on the client (which I asume to be my laptop – Unison is installed on the laptop?).

The response is: "ssh: could not resolve hostname mint-desktop: Name or service not known".

On both machines "unison -version" responds with: 2.32.52"
and "ssh -V" with: "OpenSSH_5.8pl Debian-7ubuntul, OpenSSL 1.0.0e sep 2011"

I think you may be right Nelz, it's an SSH login failure. I can't find any clues in the log file.

Could you tell me how to get started finding a problem in ssh.

Regards
gmport

Dutch_Master · LXF regular Joined: Tue Mar 27, 2007 2:49 am Posts: 2353

The fact that ssh responds when asked for its version number indicates that 1) it's installed and 2) it's running. That only leaves a connection error. By default, ssh runs on port 22 and you may have a mis-match in the config file or, more commonly, a firewall blocks access to port 22. Another common issue is exchanging the public keys: your previous setup may have done that by itself, but this one hasn't. You need to generate public and private keys and copy the public key to the other machine's trusted_hosts file in the ~/.ssh/ directory.

gmport · Joined: Fri Jan 20, 2012 3:16 pm Posts: 9

Thank you Dutch_Master,

I'm reading up how to generate and save the keys. The instructions say to save the keys on the local machine to “/home/username/.ssh/”. I don't have a hidden ssh directory on either machine. Should I already have one or should I create it?

Also, it says that the RSA key pair must be copied to the remote system with: “ssh-copy-id -i ~/.ssh/linuxlookup_rsa.pub username@example.com”. But my ssh connection is not yet working, can I just copy them 'manually' to the remote .ssh directory.

Forgive my caution, I have already had to re-install both machines after trying to do something similar that I wasn't sure how to do correctly.

Regards
gmport

Dutch_Master · LXF regular Joined: Tue Mar 27, 2007 2:49 am Posts: 2353

Are you checking the right directory? You have 2 users (that I'm aware of, there are in fact many more on your system, but no need for alarm), namely your own user (the account you log in to) and the unison user. As I understand from your earlier messages, Unison runs as the unison user, so you'd need to look in the /home/unison/ directory. However, it doesn't hurt to copy these keys to your normal user account too. If you're unsure, copy them via USB stick.

Here's another clue, overlooked first time round:

gmport · Joined: Fri Jan 20, 2012 3:16 pm Posts: 9

Hi Dutch_Master and thank you for your patience.

I opened the file /etc/hosts as you suggested but there doesn't seem to be an entry for "mint-desktop" see below:

127.0.0.1 localhost
127.0.1.1 6730s

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

127.0.0.1 must be my wireless router.

Sorry if I said something confusing earlier, but Unison is not setup as a user.

Regards
gmport

Dutch_Master · LXF regular Joined: Tue Mar 27, 2007 2:49 am Posts: 2353

No, 127.0.0.1 is the loopback address. Basically, it's a way for the machine to connect to itself. What you need to do is to add the following to this file:

Bruno · Posted: Sat Jan 21, 2012 5:13 pm Post subject:

Hi All,

Unison is now only under occasional development but bug reports, feature requests and questions are still being taken by its original developers. For more, see here. Therefore, in this case; the difference between the version numbers of your installed packages and obtained documentation should not make much difference. However, it is best to either update your packages to 2.40.61 or find the documentation for 2.32.52. When you installed unison, the package should have contained documentation, too. On my system, it is located at /usr/share/doc/packages/unison/unison-manual.html, so try there on your system or consult the file list of the package you installed if it is not there. FYI, I'm using version 2.32.52 without problems on openSUSE 11.4.

OK, as nelz says, the first thing to do is check that sshd (the ssh daemon) is running on your remote/server computer. On your server, copy and paste the following into a new, plain text file and call it something like "sshd-run-checker.sh":

gmport · Joined: Fri Jan 20, 2012 3:16 pm Posts: 9

Dutch_Master... I am so grateful adding "192.168.1.2 mint-desktop" to "/etc/hosts" fixed the problem. I can now connect to the remote PC.

Thank you for your patience.

Very best regards
gmport

gmport · Joined: Fri Jan 20, 2012 3:16 pm Posts: 9

Hi Bruno,

Thank you for the information, I don't pretend to understand it all but I shall certainly save it for future reference.

Thank you and thanks to everyone that replied to my request for help.

Best regards
gmport

Dutch_Master · LXF regular Joined: Tue Mar 27, 2007 2:49 am Posts: 2353

Most welcome, that's what this forum is all about: sharing knowledge and trying to assist in solving problems if and when they arise Smile