memprobe: 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/memprobe - from package: root-core

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

On Debian possible default full paths are:

/usr/bin/memprobe - from package: libroot-core-dev

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

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