dh_xsf_substvars: 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/bin/dh_xsf_substvars - from package: xserver-xorg-dev

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

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