fdisk: 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:

/sbin/fdisk - from package: util-linux-ng

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

On Debian possible default full paths are:

/sbin/fdisk - from package: util-linux

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

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