xenstore-exists: 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/xenstore-exists - from package: xenstore-utils

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

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