mgaps: 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/mgaps - from package: mummer

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

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