ubuntu中修改mysql的datadir

原文連接：http://www.zhanggang.net/y2010/38170.html

大概需要4個步驟，其中第1步通過service mysql stop停止數據庫，第4步通過service mysql start啓動數據庫。

第2步移動數據文件，與原文不一樣，我是爲了在ramdisk測試，所以要保留原來的數據，所以不用mv命令，直接用

cp -arf /var/lib/mysal /mnt/tmpfs

這樣子不僅複製了原有的數據，並且權限也全部拷貝過來了，連chown,chmod都給省事了。

本來以爲這樣就沒事了，啓動mysql報錯，查看日誌輸出：

InnoDB: The error means mysqld does not have the access rights to
InnoDB: the directory.
InnoDB: File name ./ibdata1
InnoDB: File operation call: 'open'.
InnoDB: Cannot continue operation.
130628  9:51:11 [Note] Plugin 'FEDERATED' is disabled.
^G/usr/sbin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)
130628  9:51:11 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.

剛纔mv過去的權限都是對的，不存在還有什麼權限的問題，到網上搜索大部分都是redhat系列的系統，其中的SElinux對ubuntu不適用，還差點真用chcon來修改所謂的安全之類的權限了

其實，在my.cnf中註釋部分說明的很清楚（但是在我的Mysql裏面就沒有看到- -！）

# * IMPORTANT
#   If you make changes to these settings and your system uses apparmor, you may
#   also need to also adjust /etc/apparmor.d/usr.sbin.mysqld.

按照說明進行第3步，註釋掉原來的路徑，增加新的路徑，2行都要修改

vi /etc/apparmor.d/usr.sbin.mysqld
#  /var/lib/mysql/ r,
#  /var/lib/mysql/** rwk,
  /tmp/tmpfs/mysql/ r,
  /tmp/tmpfs/mysql/** rwk,

更新參數

/etc/init.d/apparmor reload

第4步：

重啓Mysql

附上自動切換腳本一個，路徑自己修改：

#!/bin/bash
MYSQLCONFIG=/etc/mysql/my.cnf
APPARMOR=/etc/apparmor.d/usr.sbin.mysqld
ORIPATH=/var/lib/mysql
TARPATH=/mnt/tmpfs/mysql

if [ $# -ne 1 ];then
        echo "$0 [ harddisk | ramdisk ]"
        exit 1
elif [ $1 != "harddisk" -o $1 != "ramdisk" ];then
        option=$1
else
        echo "unknown options"
        echo "$0 [ harddisk | ramdisk ]"
        exit 1
fi

change2harddist() {
        sudo sed -i -e "s@^datadir\(.*\)@datadir=$ORIPATH@g" $MYSQLCONFIG
        sudo sed -i -e "s@$TARPATH@$ORIPATH@g" $APPARMOR
        sudo /etc/init.d/apparmor reload
}

change2ramdisk() {
        if [ ! -e "/mnt/tmpfs/mysql" ];then
                sudo -arfv /var/lib/mysql /mnt/tmpfs/mysql
        fi
        sudo sed -i -e "s@^datadir\(.*\)@datadir=$TARPATH@g" $MYSQLCONFIG
        sudo sed -i -e "s@$ORIPATH@$TARPATH@g" $APPARMOR
        sudo /etc/init.d/apparmor reload
}

mysql_control() {
        control=$1
        sudo service mysql $control
        if [ $control = "start" -a $? -ne 0 ];then
                exit 1
        fi
}

mysql_control stop
if [ $option = "harddisk" ];then
        change2harddist
elif [ $option = "ramdisk" ];then
        change2ramdisk
fi
mysql_control start