insserv: 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:

/sbin/insserv - from package: insserv

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

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