LD_LIBRARY_PATH unset by screen

screen doesn't unset the environment variable; it is removed by Linux itself.

On most systems, the /usr/bin/screen executable is installed with the setgid bit for utmp group, in order to be able to modify the utmp database. It also uses setgid to control access to the socket directory (/var/run/screen/).

On Linux, when a setuid (or setgid) program is ran, it does not receive certain environment variables (including LD_LIBRARY_PATH, several other LD_* variables, and HOSTALIASES), in order to reduce the possible attack points: Otherwise you could write a small library and trick su or sudo into calling your "improved" functions that way.

You can remove the setgid bit from screen, but you will have to make the socket directory fully accessible by everyone (mode 0777). It shouldn't be a security risk, though, as screen also checks the attacher's UID itself.

However, you should not make the utmp database world-writable.

In your .screenrc, you can use the setenv command to set a value in screen's environment.

setenv LD_LIBRARY_PATH $LD_LIBRARY_PATH_SCREEN

This is set before your shell is started. Obviously LD_LIBRARY_PATH_SCREEN needs to be set before you start screen.

Try exporting the environment variable you are interested in.

export LD_LIBRARY_PATH