memcflush: 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/memcflush - from package: libmemcached-tools

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

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