ubuntu-build: 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/bin/ubuntu-build - from package: ubuntu-dev-tools

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