update-xmlcatalog: 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/update-xmlcatalog - from package: xml-core

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

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