ytree: 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/ytree - from package: ytree

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

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