Shell Environment Variables – Difference Between /etc/environment and /etc/profile

environment-variablesposixshell

I understand that the former is loaded prior to the latter, but what is the conceptual difference? Are there any good reasons I should set some variables in one and not in other? Except the fact that /etc/environment seems to exist to set up environment for all processes run by the system, while /etc/profile is for setting up environment used and propagated from the login shell, correct?

Also, on a side note, which program traditionally reads /etc/environment? Is it related to POSIX, or just a convention?

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Extract from The Ubuntu help

/etc/environment - This file is specifically meant for system-wide environment variable settings. It is not a script file, but rather consists of assignment expressions, one per line. Specifically, this file stores the system-wide locale and path settings.

/etc/profile - This file gets executed whenever a bash login shell is entered (e.g. when logging in from the console or over ssh), as well as by the DisplayManager when the desktop session loads.

I think all this is just a convention but not far from a standard (I don't know about RedHat like systems ).

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Linux – Why does the LD_LIBRARY_PATH get unset launching terminal

The terminal binary is most likely setgid to group utmp. Setuid and setgid binaries unset LD_LIBRARY_PATH for security reasons; see ld.so(8):

The necessary shared libraries needed by the program are searched for in the following order

Using the environment variable LD_LIBRARY_PATH (LD_AOUT_LIBRARY_PATH for a.out programs). Except if the executable is a setuid/setgid binary, in which case it is ignored.

Debian – Setting environment variables in Linux for all processes

Processes (including shells) only inherit variables from their parents. There is no way to change them from the outside thereafter.

Set "global variables" as early in the boot (for system processes) or shell invocation (for user processes) as possible, or resign yourself to setting them in multiple places.

This may seem like a pain, but the ability to change another processes environment would be a bug, and would introduce all kinds of nasty race conditions.

What are you trying to do that you want "global" environment variables? There may be way to work around your problem.

Workaround:: Write a minimal script in your favorite shell format that only sets the variable you want and put it in a globally accessible place:

/etc/loglocaltion.sh:

export MY_LOG_DIR=/opt/share/mylog
export MY_DEFAULT_LOG_LEVEL=URGENT

and for everything that you want to use that configuration do one of

launch it from shell which has sourceed loglocation.sh in it's non-interactive login file (the one that gets read for all instances of the shell, i.e. .bash_profile).
write a minimal wrapper script which sources loglocation.sh before launching the real program. launchcorelogger.sh:

 CORELOGGER=/opt/sbin/mycorelogger
 source /etc/loglocation.sh
 exec $CORELOGGER

and have init run the script.

Now edits to the loglocation script will effect all associated processing if your run them from a fresh shell in the first case or restart them using you systems dameon restarted (/etc/init.d/mycorelogger restart or whatever).

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Linux – Why does the LD_LIBRARY_PATH get unset launching terminal

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