memcachedb: 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/bin/memcachedb - from package: memcachedb

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

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