sipdialer: 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 CentOS possible default full paths are:

/usr/bin/sipdialer - from package: resiprocate-sipdialer

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/sipdialer - from package: sipdialer

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

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