Permission Problems

Posted on 28 January, 2007 by maximinus in Linux

I've been running IRSSI within screen on my home server for a while now, so that I remain connected to IRC.  With my decent ADSL modem/router currently out of action, and thus reduced to using a "DeLink" (DLink) DSL-302G (which drops out randomly for no reason), remaining connected was getting difficult, so last night I decided to set up IRSSI+screen on my new VPS, since it's easy because it's running Debian Sarge (so I don't have to try to hunt down CentOS 3 RPMs for stuff).

For some reason, whilst both screen and IRSSI worked fine as root, neither would work properly as a non-root user.  At first, screen would error saying that it couldn't get a PTY - so I changed the group ownership of a bunch of PTYs to the "tty" group and added the user to this group.  This left me with screen still not giving me a prompt - just a blinking cursor.  I could, however, run "screen irssi" - which would attempt to start IRSSI inside a new screen.  IRSSI, however, had a different idea entirely.  Whenever I tried to launch it as the non-root user, whether it was in or out of screen, it would give the cryptic error:

Can't open perl script "-e": Permission denied

and then segfault.  After much googling around, I eventually found the solution in some IRC logs that a Google search turned up:

chmod a+rw /dev/null

Nobody seems to know why /dev/null may have lost these permissions, or indeed why restoring them magically makes Perl work properly for non-root users and thus allows screen and IRSSI to work nicely - but hey, it does work.