hdav: command not found

Have You tried accessing the binary with the full path?

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/hdav - from package: hdav

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