kamailio: 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:

/usr/sbin/kamailio - from package: kamailio

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

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