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

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

On Debian possible default full paths are:

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

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

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