pnmtoy4m: 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/pnmtoy4m - from package: mjpegtools

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

Error in other languages:
pnmtoy4m: bevel nie gevind nie
pnmtoy4m: comandă negăsită
pnmtoy4m: comando não encontrado
pnmtoy4m: commande introuvable
pnmtoy4m: command not found
pnmtoy4m: käsku ei ole
pnmtoy4m: không tìm thấy lệnh
pnmtoy4m: komanda nerasta
pnmtoy4m: Kommando nicht gefunden.
pnmtoy4m: kommandot finns inte
pnmtoy4m: komut yok
pnmtoy4m: nie znaleziono polecenia
pnmtoy4m: níor aimsíodh an t-ordú
pnmtoy4m: no se encontró la orden
pnmtoy4m: no s'ha trobat l'ordre
pnmtoy4m: opdracht niet gevonden
pnmtoy4m: parancs nem található
pnmtoy4m: perintah tidak ditemukan
pnmtoy4m: príkaz nenájdený
pnmtoy4m: příkaz nenalezen
pnmtoy4m: команда не найдена
pnmtoy4m: командата не е открита
pnmtoy4m: 命令找不到
pnmtoy4m: コマンドが見つかりません