Unison fails to set permissions

Unison persistently refused to synchronise new files not present on one of the machines claiming:
"Failed to set permissions of file …" (different user names and IDs, by the way).
The solution (found here) is to disable owner and permission setting in the corresponding ~/.unison/<theproject>.prf file. Add the lines
owner=false
perms=0
and you should be fine.
Update (12/2014): I ran into a permissions problem again after installing a fresh 14.10 Kubuntu while keeping my old home partition (at least I think that's what changed between Unison runs ;) ).
This time it was "Error in setting permissions". This bug discussion recommended adding a
dontchmod=true
line to the .prf file (in addition to the options listed above), which solved  my issue.

Even Macbooks do crash

A friend of mine brought her 2-year-old Macbook with the hard disk in a sorry state and asked us to salvage some files she hadn't backed up yet.
Lots of things to learn:

SSH port changes and the openSuSE firewall

Note to self - when changing the SSH port from default 22, keep in mind:

• Change listening port in Webmin (port number > 1024 recommended)
• Let Webmin handle the sighup (existing connections are kept)
• No webmin available: Change port in /etc/ssh/sshd_config (right where it says "Port") . It's easier just to restart (but all connections are killed)
  sudo /etc/init.d/ssh restart
  If you need a sighup (e.g. when you administrate over ssh):
  $ sudo -s
  # ps -alxww | grep ssh
  # kill -9 <process (3rd column) with 4th column "1">
• YaSt and firewall: YaST->Security and Users->Firewall->Allowed Services. To simply allow SSH in the drop-down list is no use, as YaST automatically assumes port 22.
  Go to "Advanced..." and open the matching TCP and UDP ports.
• Now I can't log in any more...: a ssh connection from shell needs the -p option
  $ ssh -p <portnum> <username>@<IP>;
  scp wants the -P option (capital P - can't they unify that?);
  other services like Unison (modify the profile files) or fish:// specify the portwith <user>@<IP>:<port>
• I want to mount a remote ssh share:
  sshfs -p <portnum> <username>@<IP>:<folder> <share>
  
  

Most of the research by daWuzzzz.

Webmin is great

Just to let you know: if you don't want to look for all the fancy configuration files your linux offers you and to edit them via vi, then this might be THE solution for you:

Webmin is a graphical webbrowser based configuration interface which you can access locally (or, as mentioned before via an ssh-port forwarding securely remotely) by typing in

https://localhost:10000

after a successful install in your preferred browser - well in konqueror because the current version seems to bitch with Mozilla Firefox

With webmin, administraton of an ssh server, filesharing via samba, user and group administration (and synchronization between the modules) and many more things you might find handy is just one mouse-click away [... that sounds like a Windows Ad]

Synchronise via unison and ssh

I've seen one crashed hard disk too many last week, so I decided to tackle my long overdue synchronisation issues.
Situation: 3 computers (Archimedes, Xanthippe and Tisiphone), creative work-in-progress chaos on all three of them and one ssh-accessed backup account on our server to synchronise all three accounts.
Rsync is a nice simple console backup tool which also works with ssh, but neither runs a diff nor a modification date comparison of duplicate files. Files in the source directory are written over those in the destination directory, no matter what.
Unison is more sophisticated. It comes with a nice Gtk GUI capable of diff viewing and setting file replacement rules (e.g. last modified).

Graphical secure remote server administration

In short: install webmin on the server you want to administrate remotely, but allow only connections from "localhost". Give an account of your choice - preferably not any root-like one - ssh access. Build a tunnel to your server's local port 10000
via

ssh -L <chooseaport>:localhost:10000 <username>@<IPofremotemachine>

Now you can access the remote webmin interface simply by opening a browser of your choice on your machine and typing

localhost:<chooseaport>

into the address bar. Nice easy, and secure!

Additionally: if your SSH server is listening on a different port than the standard port 22, you can connect to it using the -p option, i.e.

ssh -p <portnumber> -L <chooseaport>:localhost:10000 <username>@<IPofremotemachine>

VNC server over a secure SSH connection

The standard way provided by openSuSE to get a remote graphical login to your linux desktop is Krfb. It uses an obscure kind of 'invitation' system and I never got the hang of it. TightVNC works like any old VNC server on Linux: start a VNC X session and log in with password protection from a remote machine via a VNC viewer like Krdc (KDE3 version works for me, KDE4 doesn't). Unhappily, a VNC connection is not exactly secure, anyone sniffing into your network might find out what you are doing at the moment on the remote machine (e.g. typing passwords). A safe alternative would be to export the VNC session over a SSH tunnel as follows.