megamerger: 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/megamerger - from package: emboss

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

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