snapper: 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/snapper - from package: snapper

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

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