pambackground: 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/pambackground - from package: netpbm-progs

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

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