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

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

On Debian possible default full paths are:

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

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

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