Is there any $PATH default setting? Post: 302699923

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Top Forums UNIX for Dummies Questions & Answers Is there any $PATH default setting? Post 302699923 by bakunin on Wednesday 12th of September 2012 03:07:21 PM

09-12-2012

Registered User

Quote:

Originally Posted by yifangt

Is it /etc/profile?

Yes, it is. In fact, there are several files read when a session/shell starts:

Whenever a session starts (that is: a user logs in), a system profile is read. In most systems this is called "/etc/environment" (AIX) or "/etc/profile" (SunOS, Linux).

Then a user profile is read. On most systems it is called ".profile" and resides in the users "$HOME". Commonly in "~/.profile" a variable named "ENV" is set, which names the startup file for the shell.

After these two files the shell itself is started. Which one this is depends on the user entry in the file "/etc/passwd", which is readable by everyone. "grep" it for you own username, which will possibly look similar to:

Code:

# grep username /etc/passwd
username:x:1001:1001:username,,,,:/home/username:/bin/ksh

The last entry is the path the shells executable, in this case Korn shell.

The following part of the process is executed every time a shell starts. This is the case for every log-in-process, because as the last stage of the log-in a shell is started, but also when a script is started with a shebang ("#!") in the first line, you enter "ksh" ("bash", ...) on the command line, etc..

First, the shell reads a system-dependant startup-file. In linux (and with bash) this is "/etc/bashrc", other system/shell-combinations may have different startup files. A look in the man page of your shell will tell you which one it is.

Second, a user-dependant startup file is read. This is either the file declared via the "ENV" variable (see above) or a default file: for bash it is "~/.bashrc", for ksh it is "~/.kshrc", etc.

Every later file can override settings from an earlier run file. Because i don't like all these graphical gimmicks like coloured ls-output my startup-files on Linux systems usually are full with commands unsetting the "helpful" aliases and other fancinesses the "/etc/profile" is setting. This may seem inefficient (first setting a lot of things, than reset all these setting to zero), but i don't like to change the "original" look and feel of the Linux systems by changing the system-wide settings. This way it is only my own account which behaves like i think a Unix-account should behave.

I hope this helps.

bakunin

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LEARN ABOUT DEBIAN

sulogin

SULOGIN(8)						Linux System Administrator's Manual						SULOGIN(8)

NAME

       sulogin - Single-user login

SYNOPSIS

       sulogin [ -e ] [ -p ] [ -t SECONDS ] [ TTY ]

DESCRIPTION

       sulogin	is invoked by init(8) when the system goes into single user mode.  (This is done through an entry in inittab(5).)  Init also tries
       to execute sulogin when the boot loader (e.g., grub(8)) passes it the -b option.

       The user is prompted

	    Give root password for system maintenance
	    (or type Control-D for normal startup):

       If the root account is locked, no password prompt is displayed and sulogin behaves as if the correct password were entered.

       sulogin will be connected to the current terminal, or to the optional device that can be specified on the command line (typically /dev/con-
       sole).

       If the -t option is used then the program only waits the given number of seconds for user input.

       If  the	-p  option  is	used  then  the single-user shell is invoked with a dash as the first character in argv[0].  This causes the shell
       process to behave as a login shell.  The default is not to do this, so that the shell will  not	read  /etc/profile  or	$HOME/.profile	at
       startup.

       After the user exits the single-user shell, or presses control-D at the prompt, the system will (continue to) boot to the default runlevel.

ENVIRONMENT VARIABLES

       sulogin	looks for the environment variable SUSHELL or sushell to determine what shell to start. If the environment variable is not set, it
       will try to execute root's shell from /etc/passwd. If that fails it will fall back to /bin/sh.

       This is very valuable together with the -b option to init. To boot the system into single user mode, with  the  root  file  system  mounted
       read/write, using a special "fail safe" shell that is statically linked (this example is valid for the LILO bootprompt)

       boot: linux -b rw sushell=/sbin/sash

FALLBACK METHODS

       sulogin	checks the root password using the standard method (getpwnam) first.  Then, if the -e option was specified, sulogin examines these
       files directly to find the root password:

       /etc/passwd,
       /etc/shadow (if present)

       If they are damaged or nonexistent, sulogin will start a root shell without asking for a password. Only use the -e option if you  are  sure
       the console is physically protected against unauthorized access.

AUTHOR

       Miquel van Smoorenburg <miquels@cistron.nl>

SEE ALSO

       init(8), inittab(5).

								    17 Jan 2006 							SULOGIN(8)