yard: 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/yard - from package: yard

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

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