disk-image-get-kernel: 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/disk-image-get-kernel - from package: diskimage-builder

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

On Debian possible default full paths are:

/usr/bin/disk-image-get-kernel - from package: python-diskimage-builder

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

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