pamstretch-gen: 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/pamstretch-gen - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pamstretch-gen - from package: netpbm

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

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