xapian-replicate-server: 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 CentOS possible default full paths are:

/usr/bin/xapian-replicate-server - from package: xapian-core

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/xapian-replicate-server - from package: xapian-tools

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

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