gmemusage: 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/gmemusage - from package: gmemusage

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

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