MySQL源码安装完成后修改安装路径启动问题
在Linux上源码编译安装完mysql后，又将安装的路径进行了修改，但是发现在设置后环境变量后启动报错，如下：
[root@HServer_03 var]# mysqld_safe --user=mysql &
[1] 31248
[root@HServer_03 var]# 110422 11:04:00 mysqld_safe Logging to '/opt/mysql5156/var/HServer_03.err'.
touch: cannot touch `/opt/mysql5156/var/HServer_03.err': No such file or directory
chown: cannot access `/opt/mysql5156/var/HServer_03.err': No such file or directory
110422 11:04:00 mysqld_safe The file /opt/mysql5156/libexec/mysqld
does not exist or is not executable. Please cd to the mysql installation
directory and restart this script from there as follows:
./bin/mysqld_safe&
See http://dev.mysql.com/doc/mysql/en/mysqld-safe.html for more information
/usr/local/mysql/bin/mysqld_safe: line 100: /opt/mysql5156/var/HServer_03.err: No such file or directory
[1]+ Exit 1 mysqld_safe --user=mysql
按照提示原有的路径目录不存在，需要到mysql的相对路径下启动～
我的原安装路径是在/opt/mysql5156下，具体的安装过程：
Shell> tar –zxvvf mysql-5.1.56.tar.gz
Shell> cd mysql-5.1.56
Shell> ./configure --prefix=/opt/mysql5156 \
--with-charset=utf8 --with-collation=utf8_general_ci \
--with-extra-charsets=latin1,gb2312 \
--with-plugins=innobase,innodb_plugin,myisam,heap,csv,federated,blackhole \
--enable-local-infile --enable-thread-safe-client
Shell> make
Shell >make install
Shell> cp support-files/my-medium.cnf /etc/my.cnf
Shell>cd /opt/mysql5156
Shell>chown –R mysql .
Shell>chgrp –R mysql .
Shell>bin/mysql_install_db –user=mysql
Shell>chown –R root .
Shell> chown –R mysql var
Shell>vi /root/.bash_profile
PATH=$PATH:$HOME/bin:/opt/mysql5156/bin
现在将/opt/mysql5156/目录移动到/usr/local/下：
Shell>mv /opt/mysql5156 /usr/local/mysql
Shell>vi /root/.bash_profile
PATH=$PATH:$HOME/bin:/usr/local/mysql/bin
Shell>source /root/.bash_profile
在启动时出现上述错误的主要原因是mysql在编译安装时，将路径/opt/mysql5156写入了mysql/bin/mysqld_safe脚本中，打开该脚本可以明确看到各个启动逻辑的判断都有/opt/mysql5156的影子，那么将所有的/opt/mysql5156 全局替换为/usr/local/mysql，保存后重新启动，ok了。
另外由于这次的编译安装时采用动态编译的，还需要修改mysql的动态函式库，
Shell>vi /etc/ld.so.conf
/usr/local/mysql/lib/mysql/
Shell>ldconfig
这样在新的路径下，编译安装的mysql就可以无碍使用了。