pbmtoibm23xx: 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/pbmtoibm23xx - from package: netpbm-progs

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

Error in other languages:
pbmtoibm23xx: bevel nie gevind nie
pbmtoibm23xx: comandă negăsită
pbmtoibm23xx: comando não encontrado
pbmtoibm23xx: commande introuvable
pbmtoibm23xx: command not found
pbmtoibm23xx: käsku ei ole
pbmtoibm23xx: không tìm thấy lệnh
pbmtoibm23xx: komanda nerasta
pbmtoibm23xx: Kommando nicht gefunden.
pbmtoibm23xx: kommandot finns inte
pbmtoibm23xx: komut yok
pbmtoibm23xx: nie znaleziono polecenia
pbmtoibm23xx: níor aimsíodh an t-ordú
pbmtoibm23xx: no se encontró la orden
pbmtoibm23xx: no s'ha trobat l'ordre
pbmtoibm23xx: opdracht niet gevonden
pbmtoibm23xx: parancs nem található
pbmtoibm23xx: perintah tidak ditemukan
pbmtoibm23xx: príkaz nenájdený
pbmtoibm23xx: příkaz nenalezen
pbmtoibm23xx: команда не найдена
pbmtoibm23xx: командата не е открита
pbmtoibm23xx: 命令找不到
pbmtoibm23xx: コマンドが見つかりません