dig: 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/dig - from package: bind-utils

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

On Debian possible default full paths are:

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

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

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