sks: 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/sks - from package: sks

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

On Debian possible default full paths are:

/usr/sbin/sks - from package: sks

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

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