yagi: 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/yagi - from package: yagiuda

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

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