unrpm: 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 Debian possible default full paths are:

/usr/bin/unrpm - from package: obs-build

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

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