rstart: 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/rstart - from package: x11-session-utils

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

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