pamcomp: 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/pamcomp - from package: netpbm-progs

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

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