pbuilder: 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/sbin/pbuilder - from package: pbuilder

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

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