set-netboot-1st-efi-nvram: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/sbin/set-netboot-1st-efi-nvram - from package: clonezilla

You may install the required package with command apt-get install {package}
Error in other languages:
set-netboot-1st-efi-nvram: bevel nie gevind nie
set-netboot-1st-efi-nvram: comandă negăsită
set-netboot-1st-efi-nvram: comando não encontrado
set-netboot-1st-efi-nvram: commande introuvable
set-netboot-1st-efi-nvram: command not found
set-netboot-1st-efi-nvram: käsku ei ole
set-netboot-1st-efi-nvram: không tìm thấy lệnh
set-netboot-1st-efi-nvram: komanda nerasta
set-netboot-1st-efi-nvram: Kommando nicht gefunden.
set-netboot-1st-efi-nvram: kommandot finns inte
set-netboot-1st-efi-nvram: komut yok
set-netboot-1st-efi-nvram: nie znaleziono polecenia
set-netboot-1st-efi-nvram: níor aimsíodh an t-ordú
set-netboot-1st-efi-nvram: no se encontró la orden
set-netboot-1st-efi-nvram: no s'ha trobat l'ordre
set-netboot-1st-efi-nvram: opdracht niet gevonden
set-netboot-1st-efi-nvram: parancs nem található
set-netboot-1st-efi-nvram: perintah tidak ditemukan
set-netboot-1st-efi-nvram: príkaz nenájdený
set-netboot-1st-efi-nvram: příkaz nenalezen
set-netboot-1st-efi-nvram: команда не найдена
set-netboot-1st-efi-nvram: командата не е открита
set-netboot-1st-efi-nvram: 命令找不到
set-netboot-1st-efi-nvram: コマンドが見つかりません