d8: 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/d8 - from package: v8

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

Error in other languages:
d8: bevel nie gevind nie
d8: comandă negăsită
d8: comando não encontrado
d8: commande introuvable
d8: command not found
d8: käsku ei ole
d8: không tìm thấy lệnh
d8: komanda nerasta
d8: Kommando nicht gefunden.
d8: kommandot finns inte
d8: komut yok
d8: nie znaleziono polecenia
d8: níor aimsíodh an t-ordú
d8: no se encontró la orden
d8: no s'ha trobat l'ordre
d8: opdracht niet gevonden
d8: parancs nem található
d8: perintah tidak ditemukan
d8: príkaz nenájdený
d8: příkaz nenalezen
d8: команда не найдена
d8: командата не е открита
d8: 命令找不到
d8: コマンドが見つかりません