memcached: 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/memcached - from package: memcached

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

On Debian possible default full paths are:

/usr/bin/memcached - from package: memcached

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

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