cernlib: 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/cernlib - from package: cernlib-utils

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

On Debian possible default full paths are:

/usr/bin/cernlib - from package: cernlib-base-dev

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

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