conntrackd: 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/sbin/conntrackd - from package: conntrack-tools

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

On Debian possible default full paths are:

/usr/sbin/conntrackd - from package: conntrackd

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

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