copydatabase: 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/copydatabase - from package: xapian-core

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

On Debian possible default full paths are:

/usr/bin/copydatabase - from package: xapian-tools

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

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