gl-screenshot: 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/share/drbl/setup/files/gparted/usr/bin/gl-screenshot - from package: clonezilla

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

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