update-apt-xapian-index: 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-apt-xapian-index - from package: apt-xapian-index

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

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