ubirmvol: command not found

Have You tried accessing the binary with the full path?

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/sbin/ubirmvol - from package: mtd-utils

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