cksum: 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/cksum - from package: coreutils

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

On Debian possible default full paths are:

/usr/bin/cksum - from package: coreutils

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

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