git-pbuilder: 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

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/git-pbuilder - from package: git-buildpackage

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