Restoring your custom software after a Synology DSM update

A few weeks ago, I finally got round to updating my Synology DS214se NAS from DSM 4 to DSM 5.1

The update process was relatively painless, but when I came to back up my videos onto an external USB drive I found the screen command was no longer recognised.

I’d heard that DSM updates could mess with previously-installed custom packages on your Diskstation, and being a Mac user, I’m used to operating system updates scuppering the “unsupported” settings or software I might have installed on my Mac.

So I headed over to my blog post on the subject, to get screen installed again. But then I thought: what if my custom programs are there, but they’re just inaccessible?

I found out that ipkg installs its software in the /opt/bin directory, and sure enough, /opt/bin was there. But when I printed out the $PATH (the list of places my SSH user account expects to find programs to run), /opt/bin wasn’t there.

Custom programs installed in /opt/bin but not accessible on the $PATH

It looks like the DSM update just overwrote the ~/.profile file that adds /opt/bin to the $PATH. To get my programs running again, I just needed to add it back again.

DSM comes with only one text editor by default: vi. Use it to open the ~/.profile

diskstation> vi ~/.profile

Add :/opt/bin to the end of the line that defines the $PATH environment variable, and save and close the file.2

All the programs in /opt/bin will now be accessible in the terminal as normal – next time you SSH in. Your current SSH session will still be using the old value of $PATH. To reload it, run your ~/.profile script manually…

diskstation> source ~/.profile

Sorted! — Or, not quite. When I tried to actually run the screen program, I got another error:

diskstation> screen
Cannot find termcap entry for 'xterm-256color'.

Tedious! Looks like the DSM update broke something else too. Like the previous problem, it was down to the ~/.profile being overwritten. Adding an explicit value for the $TERM environment variable makes screen happy again. So repeat the vi steps above, except this time, add a new line at the bottom of the file:3

export TERM=xterm

Now, when you refresh the session with source ~/.profile again, screen will open up just fine, and you can get back to whatever you wanted to do before.

The moral of the story is: DSM updates don’t seem to uninstall custom software from /opt/bin but they do overwrite ~/.profile so any modifications you’ve made to your environment might need to be re-made after the update.

  1. DSM (Disk Station Manager) is the Linux-based operating system that Synology devices run. Its most obvious manifestation is the browser-based GUI it gives Synology users to manage their devices. But DSM also intertwines with the underlying Linux operating system, so a major DSM update can have significant impact on command line access, if you’re accustomed to SSHing into your Diskstation.

  2. If you’re lost, use i to enter insert mode, use the arrow keys to move down to the line that starts with PATH=, press $ to move to the end of the line, then type :/opt/bin, then, once it’s added properly, press the Escape key to exit insert mode, then type :wq to save the file and quit.

  3. The eagle-eyed amongst you will notice ~/.profile already contains two lines that set the $TERM variable. If you want, you could amend them directly, rather than adding a new export TERM at the end of the file. But my way is simpler for newbies, and works just as well.