update-hostname-from-ip: 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

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/sbin/update-hostname-from-ip - from package: debian-edu-config

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