kdig: 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/kdig - from package: knot

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

On Debian possible default full paths are:

/usr/bin/kdig - from package: knot-dnsutils

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

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