mummer: 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/mummer - from package: mummer

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

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