update-gosa: 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/sbin/update-gosa - from package: gosa

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