pbmtobbnbg: 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/pbmtobbnbg - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pbmtobbnbg - from package: netpbm

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

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