rmmer_1: 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/rmmer_1 - from package: mh-book

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

Error in other languages:
rmmer_1: bevel nie gevind nie
rmmer_1: comandă negăsită
rmmer_1: comando não encontrado
rmmer_1: commande introuvable
rmmer_1: command not found
rmmer_1: käsku ei ole
rmmer_1: không tìm thấy lệnh
rmmer_1: komanda nerasta
rmmer_1: Kommando nicht gefunden.
rmmer_1: kommandot finns inte
rmmer_1: komut yok
rmmer_1: nie znaleziono polecenia
rmmer_1: níor aimsíodh an t-ordú
rmmer_1: no se encontró la orden
rmmer_1: no s'ha trobat l'ordre
rmmer_1: opdracht niet gevonden
rmmer_1: parancs nem található
rmmer_1: perintah tidak ditemukan
rmmer_1: príkaz nenájdený
rmmer_1: příkaz nenalezen
rmmer_1: команда не найдена
rmmer_1: командата не е открита
rmmer_1: 命令找不到
rmmer_1: コマンドが見つかりません