Ubuntu recently informed me that I used up all disk space and need to free some more.
After few hours spent looking for guilty party, I found out that my .xsession-errors file size is 37.1 GiB!
I haven't read it completely (thank GNU for less and its ability to read only parts of files!), but most common errors appear to be
(npviewer.bin:2918): Gdk-WARNING **: XID collision, trouble ahead /usr/share/themes/NOX/gtk-2.0/gtkrc:233: Murrine configuration option "gradients" is no longer supported and will be ignored. [0x7fc5d4023518] pulse audio output: No. of Audio Channels: 2 *** NSPlugin Viewer *** WARNING: unhandled variable 18 (<unknown variable>) in NPN_GetValue()
For comparison old .xsession-errors was around 10 KiB.
This is in my opinion very strange.
My question is : How do I found out what's causing such behavior and how to stop it?