Why and How To Customize a UNIX / Linux User Account?

Q. Can you tell more about UNIX user account customization along with some sample configuration?

A. Usually useradd / adduser and passwd commands are used for creating an entry for a user in /etc/passwd, /etc/shadow and /etc/group files. However, adding user in files may not provide all the functionality needed. You need to set user customization by modifying various scripts located at /etc or ~/ (user home directory). These scripts executed at the start of every console (text based) login or ssh session to setup the user's environment.

Typical UNIX / Linux login scenario

User login / SSH Login
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System login script /etc/profile
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Personal login script $HOME/.profile
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Shell startup script $HOME/.bash_profile $HOME/.shrc
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User logged in (login complete)

You can add system wide customization using /etc/profile file. End users can manage their own profile / custom environment using personal login script or shell startup script.

Why customize a UNIX / Linux / BSD user account?

Following are few common examples:

Set the JDK / JVM / PATH variables
Set the user's terminal type
Customize the user's prompt
Set a default text editor
Setup historyfile size and location
Run reports as soon as you log into account etc
Set a command line shortcuts and aliases

Sample Customization

$ cat ~/.bash_profile
Output:
export TERM=xterm # my terminal type export PS1="$ " # my sweet prompt export JAVA_HOME=/opt/jvm/java-6-sun #for java export PATH=$PATH:$JAVA_HOME/bin:/home/vivek/bin # my binary file search path export EDITOR=vim # my editor export HISTSIZE=100 # history file size export HISTFILE=~/.cmd_history # history file location umask 077 # my umask ulimit -c 0 # unlimited core file # some shell variables set -o noclobber set -o physical shopt -s cdspell shopt -s extglob shopt -s dotglob shopt -s cmdhist shopt -s lithist shopt -s progcomp shopt -s checkhash shopt -s histreedit shopt -s promptvars shopt -s cdable_vars shopt -s checkwinsize shopt -s hostcomplete shopt -s expand_aliases shopt -s interactive_comments bind '"\C-t": possible-completions' # replaces 'transpose-chars' bind '"\M-t": menu-complete' # replaces 'transpose-words'

View environment variables list

Simply user env command, enter:
$ env

/etc/skel directory to push configuration to user

By default all files from /etc/skel are copied to the new user's home directory; when a new user account created. There are few files included in /etc/skel/ by default.

/etc/skel/.bash_logout
/etc/skel/.bashrc
/etc/skel/.profile
/etc/skel/.cshrc
/etc/skel/.exrc (/etc/skel/.vimrc)

You can also create or copy existing scripts in /etc/skel. For example copy /usr/share/vim/vimrc to /etc/skel/.vimrc
# cp /usr/share/vim/vimrc /etc/skel/.vimrc
Now file /etc/skel/.vimrc will be copied when a new user account created.

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