rpm2cpio: 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/rpm2cpio - from package: rpm

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

On Debian possible default full paths are:

/usr/bin/rpm2cpio - from package: rpm2cpio

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

Error in other languages:
rpm2cpio: bevel nie gevind nie
rpm2cpio: comandă negăsită
rpm2cpio: comando não encontrado
rpm2cpio: commande introuvable
rpm2cpio: command not found
rpm2cpio: käsku ei ole
rpm2cpio: không tìm thấy lệnh
rpm2cpio: komanda nerasta
rpm2cpio: Kommando nicht gefunden.
rpm2cpio: kommandot finns inte
rpm2cpio: komut yok
rpm2cpio: nie znaleziono polecenia
rpm2cpio: níor aimsíodh an t-ordú
rpm2cpio: no se encontró la orden
rpm2cpio: no s'ha trobat l'ordre
rpm2cpio: opdracht niet gevonden
rpm2cpio: parancs nem található
rpm2cpio: perintah tidak ditemukan
rpm2cpio: príkaz nenájdený
rpm2cpio: příkaz nenalezen
rpm2cpio: команда не найдена
rpm2cpio: командата не е открита
rpm2cpio: 命令找不到
rpm2cpio: コマンドが見つかりません