walrus: 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/walrus - from package: mpdcron

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

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