mysql: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/mysql - from package: mysql55w
/usr/bin/mysql - from package: mysql

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/mysql - from package: mariadb-client-core-10.0
/usr/bin/mysql - from package: mysql-client-5.5

You may install the required package with command apt-get install {package}

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