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

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

On Debian possible default full paths are:

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

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

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