memory_info: 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/lib/plainbox-providers-1/checkbox/bin/memory_info - from package: plainbox-provider-checkbox

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

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