环境：RHEL 6.5
RHEL使用Bourne Again shell（Bash），本文介绍其初始化过程。
首先明确两个概念：
（1）交互式 shell：指用户在提示符下输命令的shell，而非执行脚本的shell。
（2）登录 shell：指在输入用户名和密码登录后得到的shell。
1. 交互式登录 shell
用户输入用户名和密码登录后，Bash初始化过程如下：
/etc/profile->~/.bash_profile->~/.bashrc—>/etc/bashrc—>~.bash_logout
（1）/etc/profile 文件内容：
# /etc/profile
# System wide environment and startup programs, for login setup
# Functions and aliases go in /etc/bashrc
# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.
pathmunge () {
case ":${PATH}:" in
*:"$1":*)
;;
*)
if [ "$2" = "after" ] ; then
PATH=$PATH:$1
else
PATH=$1:$PATH
fi
esac
}
if [ -x /usr/bin/id ]; then
if [ -z "$EUID" ]; then
# ksh workaround
EUID=`id -u`
UID=`id -ru`
fi
USER="`id -un`"
LOGNAME=$USER
MAIL="/var/spool/mail/$USER"
fi
# Path manipulation
if [ "$EUID" = "0" ]; then
pathmunge /sbin
pathmunge /usr/sbin
pathmunge /usr/local/sbin
else
pathmunge /usr/local/sbin after
pathmunge /usr/sbin after
pathmunge /sbin after
fi
HOSTNAME=`/bin/hostname 2>/dev/null`
HISTSIZE=1000
if [ "$HISTCONTROL" = "ignorespace" ] ; then
export HISTCONTROL=ignoreboth
else
export HISTCONTROL=ignoredups
fi
export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL
# By default, we want umask to get set. This sets it for login shell
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then
umask 002
else
umask 022
fi
for i in /etc/profile.d/*.sh ; do
if [ -r "$i" ]; then
if [ "${-#*i}" != "$-" ]; then
. "$i"
else
. "$i" >/dev/null 2>&1
fi
fi
done
unset i
unset -f pathmunge
（2）~/.bash_profile 文件内容：
# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
# User specific environment and startup programs
PATH=$PATH:$HOME/bin
export PATH
（3）~/.bashrc 文件内容：
# .bashrc
# Source global definitions
if [ -f /etc/bashrc ]; then
. /etc/bashrc
fi
# User specific aliases and functions
（4）/etc/bashrc 文件内容：
# /etc/bashrc
# System wide functions and aliases
# Environment stuff goes in /etc/profile
# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.
# are we an interactive shell?
if [ "$PS1" ]; then
if [ -z "$PROMPT_COMMAND" ]; then
case $TERM in
xterm*)
if [ -e /etc/sysconfig/bash-prompt-xterm ]; then
PROMPT_COMMAND=/etc/sysconfig/bash-prompt-xterm
else
PROMPT_COMMAND='printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'
fi
;;
screen)
if [ -e /etc/sysconfig/bash-prompt-screen ]; then
PROMPT_COMMAND=/etc/sysconfig/bash-prompt-screen
else
PROMPT_COMMAND='printf "\033]0;%s@%s:%s\033\\" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'
fi
;;
*)
[ -e /etc/sysconfig/bash-prompt-default ] && PROMPT_COMMAND=/etc/sysconfig/bash-prompt-default
;;
esac
fi
# Turn on checkwinsize
shopt -s checkwinsize
[ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@\h \W]\\$ "
# You might want to have e.g. tty in prompt (e.g. more virtual machines)
# and console windows
# If you want to do so, just add e.g.
# if [ "$PS1" ]; then
# PS1="[\u@\h:\l \W]\\$ "
# fi
# to your custom modification shell script in /etc/profile.d/ directory
fi
if ! shopt -q login_shell ; then # We're not a login shell
# Need to redefine pathmunge, it get's undefined at the end of /etc/profile
pathmunge () {
case ":${PATH}:" in
*:"$1":*)
;;
*)
if [ "$2" = "after" ] ; then
PATH=$PATH:$1
else
PATH=$1:$PATH
fi
esac
}
# By default, we want umask to get set. This sets it for non-login shell.
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then
umask 002
else
umask 022
fi
# Only display echos from profile.d scripts if we are no login shell
# and interactive - otherwise just process them to set envvars
for i in /etc/profile.d/*.sh; do
if [ -r "$i" ]; then
if [ "$PS1" ]; then
. "$i"
else
. "$i" >/dev/null 2>&1
fi
fi
done
unset i
unset pathmunge
fi
# vim:ts=4:sw=4
RHEL使用Bourne Again shell（Bash），本文介绍其初始化过程。
首先明确两个概念：
（1）交互式 shell：指用户在提示符下输命令的shell，而非执行脚本的shell。
（2）登录 shell：指在输入用户名和密码登录后得到的shell。
1. 交互式登录 shell
用户输入用户名和密码登录后，Bash初始化过程如下：
/etc/profile->~/.bash_profile->~/.bashrc—>/etc/bashrc—>~.bash_logout
（1）/etc/profile 文件内容：
# /etc/profile
# System wide environment and startup programs, for login setup
# Functions and aliases go in /etc/bashrc
# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.
pathmunge () {
case ":${PATH}:" in
*:"$1":*)
;;
*)
if [ "$2" = "after" ] ; then
PATH=$PATH:$1
else
PATH=$1:$PATH
fi
esac
}
if [ -x /usr/bin/id ]; then
if [ -z "$EUID" ]; then
# ksh workaround
EUID=`id -u`
UID=`id -ru`
fi
USER="`id -un`"
LOGNAME=$USER
MAIL="/var/spool/mail/$USER"
fi
# Path manipulation
if [ "$EUID" = "0" ]; then
pathmunge /sbin
pathmunge /usr/sbin
pathmunge /usr/local/sbin
else
pathmunge /usr/local/sbin after
pathmunge /usr/sbin after
pathmunge /sbin after
fi
HOSTNAME=`/bin/hostname 2>/dev/null`
HISTSIZE=1000
if [ "$HISTCONTROL" = "ignorespace" ] ; then
export HISTCONTROL=ignoreboth
else
export HISTCONTROL=ignoredups
fi
export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL
# By default, we want umask to get set. This sets it for login shell
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then
umask 002
else
umask 022
fi
for i in /etc/profile.d/*.sh ; do
if [ -r "$i" ]; then
if [ "${-#*i}" != "$-" ]; then
. "$i"
else
. "$i" >/dev/null 2>&1
fi
fi
done
unset i
unset -f pathmunge
（2）~/.bash_profile 文件内容：
# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
# User specific environment and startup programs
PATH=$PATH:$HOME/bin
export PATH
（3）~/.bashrc 文件内容：
# .bashrc
# Source global definitions
if [ -f /etc/bashrc ]; then
. /etc/bashrc
fi
# User specific aliases and functions
（4）/etc/bashrc 文件内容：
# /etc/bashrc
# System wide functions and aliases
# Environment stuff goes in /etc/profile
# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.
# are we an interactive shell?
if [ "$PS1" ]; then
if [ -z "$PROMPT_COMMAND" ]; then
case $TERM in
xterm*)
if [ -e /etc/sysconfig/bash-prompt-xterm ]; then
PROMPT_COMMAND=/etc/sysconfig/bash-prompt-xterm
else
PROMPT_COMMAND='printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'
fi
;;
screen)
if [ -e /etc/sysconfig/bash-prompt-screen ]; then
PROMPT_COMMAND=/etc/sysconfig/bash-prompt-screen
else
PROMPT_COMMAND='printf "\033]0;%s@%s:%s\033\\" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/~}"'
fi
;;
*)
[ -e /etc/sysconfig/bash-prompt-default ] && PROMPT_COMMAND=/etc/sysconfig/bash-prompt-default
;;
esac
fi
# Turn on checkwinsize
shopt -s checkwinsize
[ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@\h \W]\\$ "
# You might want to have e.g. tty in prompt (e.g. more virtual machines)
# and console windows
# If you want to do so, just add e.g.
# if [ "$PS1" ]; then
# PS1="[\u@\h:\l \W]\\$ "
# fi
# to your custom modification shell script in /etc/profile.d/ directory
fi
if ! shopt -q login_shell ; then # We're not a login shell
# Need to redefine pathmunge, it get's undefined at the end of /etc/profile
pathmunge () {
case ":${PATH}:" in
*:"$1":*)
;;
*)
if [ "$2" = "after" ] ; then
PATH=$PATH:$1
else
PATH=$1:$PATH
fi
esac
}
# By default, we want umask to get set. This sets it for non-login shell.
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`id -gn`" = "`id -un`" ]; then
umask 002
else
umask 022
fi
# Only display echos from profile.d scripts if we are no login shell
# and interactive - otherwise just process them to set envvars
for i in /etc/profile.d/*.sh; do
if [ -r "$i" ]; then
if [ "$PS1" ]; then
. "$i"
else
. "$i" >/dev/null 2>&1
fi
fi
done
unset i
unset pathmunge
fi
# vim:ts=4:sw=4
2. 交互式非登录 shell
如何得到一个交互式非登录 shell ? 有两种最简单的方式：
（1）在图形界面下，打开一个终端窗口。
（2）在登录shell提示符下再输入bash命令。
以这样的方式得到的互式非登录 shell ，初始化过程是这样的：~/.bashrc—>/etc/bashrc。
这里特别要强调的是，交互式非登录 shell没有执行/etc/profile和~/.bash_profile，但是继承了登录 shell的初始化设置（因为毕竟第一次是登录进来的嘛）。
3. 为什么登录shell和非登录shell的初始化过程不一样呢？
从字符终端或者远程登录得到的登录shell是该用户的所有其它进程的父进程，也是其它子shell的父进程，所以环境变量在登录shell的启动脚本里设置一次就可以自动带到其它非登录shell里。
而非登录shell的本地变量、函数、alias等设置没有办法带到子shell里，需要每次启动非登录shell时再设置一遍。
结论：
（1）在 /etc/proflie 中设置全局环境变量，对所有用户生效，只在用户登录时执行一次。
（2）在 ~/.bash_profile 中设置本地环境变量，对单一用户生效，只在用户登录时执行一次。
~/.bash_profile和/etc/profile的关系可以类比Windows下的用户环境变量设置和系统环境变量设置。
（3）在 ~/.bashrc 中设置本地变量、函数、alias等，对单一用户生效，在用户登录或打开新shell时执行。
（4）/etc/bashrc 在用户登录或打开新shell时执行。
（5）~.bash_logout 在用户退出shell时被执行。
如何得到一个交互式非登录 shell ? 有两种最简单的方式：
（1）在图形界面下，打开一个终端窗口。
（2）在登录shell提示符下再输入bash命令。
以这样的方式得到的互式非登录 shell ，初始化过程是这样的：~/.bashrc—>/etc/bashrc。
这里特别要强调的是，交互式非登录 shell没有执行/etc/profile和~/.bash_profile，但是继承了登录 shell的初始化设置（因为毕竟第一次是登录进来的嘛）。
3. 为什么登录shell和非登录shell的初始化过程不一样呢？
从字符终端或者远程登录得到的登录shell是该用户的所有其它进程的父进程，也是其它子shell的父进程，所以环境变量在登录shell的启动脚本里设置一次就可以自动带到其它非登录shell里。
而非登录shell的本地变量、函数、alias等设置没有办法带到子shell里，需要每次启动非登录shell时再设置一遍。
结论：
（1）在 /etc/proflie 中设置全局环境变量，对所有用户生效，只在用户登录时执行一次。
（2）在 ~/.bash_profile 中设置本地环境变量，对单一用户生效，只在用户登录时执行一次。
~/.bash_profile和/etc/profile的关系可以类比Windows下的用户环境变量设置和系统环境变量设置。
（3）在 ~/.bashrc 中设置本地变量、函数、alias等，对单一用户生效，在用户登录或打开新shell时执行。
（4）/etc/bashrc 在用户登录或打开新shell时执行。
（5）~.bash_logout 在用户退出shell时被执行。
参考文献：
1. http://blog.csdn.net/ctthuangcheng/article/details/17161463
2. http://blog.csdn.net/guosha/article/details/3334477
3. http://www.linuxde.net/2013/10/15352.html
4. http://blog.csdn.net/chlstar/article/details/7170601
5. http://linux.chinaitlab.com/administer/929819.html
3. http://www.linuxde.net/2013/10/15352.html
4. http://blog.csdn.net/chlstar/article/details/7170601
5. http://linux.chinaitlab.com/administer/929819.html
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