drmmer: 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/share/doc/mh-book/examples/mh/bin/drmmer - from package: mh-book

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

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