mysqld: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/sbin/mysqld - from package: mariadb-server-core-10.0
/usr/sbin/mysqld - from package: mysql-server-core-5.5

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