myrescue: 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/sbin/myrescue - from package: myrescue

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

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