针对Linux系统自带Mysql 数据库不能使用的情况，可能是在安装过程有没有安装mysql server， 安装时即使选了安装MYSQL（图形界面安装），只有打开旁边“细节”，从里面勾选选上server才可以。
安装完成后在/usr/bin 目录下会生成许多MySQL的相关文件，其中有一个名为mysqld_safe 启动服务的脚本文件，执行这个脚本文件后，发现错误'/var/lib/mysql/mysql.sock'， 查看mysql服务才发现，没有起来，于是执行/etc/init.d/mysqld start，启动服务后，在/usr/bin 执行mysql 成功进入数据库！
[pan@localhost ~]$ su – root
Password:
[root@localhost ~]# cd /usr/bin
[root@localhost bin]# ./mysqld_safe --user=root &
[1] 12969
[root@localhost bin]# Starting mysqld daemon with databases from /var/lib/mysql
STOPPING server from pid file /var/run/mysqld/mysqld.pid
090606 15:20:04 mysqld ended
mysql
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
[1]+ Done ./mysqld_safe --user=root
[root@localhost bin]# mysql
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
[root@localhost bin]# /etc/rc.d/init.d/mysqld status
mysqld is stopped
[root@localhost bin]# /etc/init.d/mysqld start （或者service mysqld restart，而service mysqld stop 停止mysql的服务）
Initializing MySQL database: [ OK ]
Starting MySQL: [ OK ]
[root@localhost bin]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2 to server version:
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql>
现在进行环境变量的配置，可以针对用户配置用户的环境变量，以root用户例，
[root@localhost bin]# cd
[root@localhost ~]# ls –a （ .bash_profile 是个隐藏文件，所以要-a）
. Desktop .gstreamer-0.8 .mozilla
.. .dmrc .gtkrc .mysql_history
anaconda-ks.cfg .eggcups .gtkrc-1.2-gnome2 .nautilus
.bash_history .fullcircle .ICEauthority .recently-used
.bash_logout .gconf .icons .rhn-applet.conf
.bash_profile .gconfd install.log .tcshrc
.bashrc .gnome install.log.syslog .viminfo
.config .gnome2 .kde .xauthC1s54N
.cshrc .gnome2_private .metacity .xautheKBniS
[root@localhost ~]# vi .bash_profile （进行修改）
# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
# User specific environment and startup programs
PATH=$PATH:$HOME/bin:/usr/bin （此处添加注意冒号）
export PATH
unset USERNAME
[root@localhost ~]# source .bash_profile （更新一下配置文件）
也可以针对系统环境配置，如下：
[root@localhost ~]# vi /etc/profile
# /etc/profile
# System wide environment and startup programs, for login setup
# Functions and aliases go in /etc/bashrc
pathmunge () {
if ! echo $PATH | /bin/egrep -q "(^|:)$1($|:)" ; then
if [ "$2" = "after" ] ; then
PATH=$PATH:$1
else
PATH=$1:$PATH
fi
fi
}
# Path manipulation
if [ `id -u` = 0 ]; then
pathmunge /sbin
pathmunge /usr/sbin
pathmunge /usr/local/sbin
pathmunge /usr/bin
fi