yorick: 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/lib/debug/usr/lib/yorick/bin/yorick - from package: yorick-dbg
/usr/bin/yorick - from package: yorick
/usr/lib/yorick/bin/yorick - from package: yorick

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

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