install-kernel-for-client: 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/share/drbl/sbin/install-kernel-for-client - from package: drbl

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