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

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

On Debian possible default full paths are:

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

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

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