xcf2pnm: 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 Debian possible default full paths are:

/usr/bin/xcf2pnm - from package: xcftools

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

Error in other languages:
xcf2pnm: bevel nie gevind nie
xcf2pnm: comandă negăsită
xcf2pnm: comando não encontrado
xcf2pnm: commande introuvable
xcf2pnm: command not found
xcf2pnm: käsku ei ole
xcf2pnm: không tìm thấy lệnh
xcf2pnm: komanda nerasta
xcf2pnm: Kommando nicht gefunden.
xcf2pnm: kommandot finns inte
xcf2pnm: komut yok
xcf2pnm: nie znaleziono polecenia
xcf2pnm: níor aimsíodh an t-ordú
xcf2pnm: no se encontró la orden
xcf2pnm: no s'ha trobat l'ordre
xcf2pnm: opdracht niet gevonden
xcf2pnm: parancs nem található
xcf2pnm: perintah tidak ditemukan
xcf2pnm: príkaz nenájdený
xcf2pnm: příkaz nenalezen
xcf2pnm: команда не найдена
xcf2pnm: командата не е открита
xcf2pnm: 命令找不到
xcf2pnm: コマンドが見つかりません