knotd: 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/knotd - from package: knot

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

On Debian possible default full paths are:

/usr/sbin/knotd - from package: knot

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

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