memflush: 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/memflush - from package: libmemcached10
/usr/bin/memflush - from package: libmemcached

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

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