mdb_copy: 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/mdb_copy - from package: lmdb

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

On Debian possible default full paths are:

/usr/bin/mdb_copy - from package: lmdb-utils

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

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