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

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

On Debian possible default full paths are:

/usr/bin/mysqld_safe - from package: mariadb-server-10.0
/usr/bin/mysqld_safe - from package: mysql-server-5.5

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

Error in other languages:
mysqld_safe: bevel nie gevind nie
mysqld_safe: comandă negăsită
mysqld_safe: comando não encontrado
mysqld_safe: commande introuvable
mysqld_safe: command not found
mysqld_safe: käsku ei ole
mysqld_safe: không tìm thấy lệnh
mysqld_safe: komanda nerasta
mysqld_safe: Kommando nicht gefunden.
mysqld_safe: kommandot finns inte
mysqld_safe: komut yok
mysqld_safe: nie znaleziono polecenia
mysqld_safe: níor aimsíodh an t-ordú
mysqld_safe: no se encontró la orden
mysqld_safe: no s'ha trobat l'ordre
mysqld_safe: opdracht niet gevonden
mysqld_safe: parancs nem található
mysqld_safe: perintah tidak ditemukan
mysqld_safe: príkaz nenájdený
mysqld_safe: příkaz nenalezen
mysqld_safe: команда не найдена
mysqld_safe: командата не е открита
mysqld_safe: 命令找不到
mysqld_safe: コマンドが見つかりません