mm2gv: 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 CentOS possible default full paths are:

/usr/bin/mm2gv - from package: graphviz

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/mm2gv - from package: graphviz

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

Error in other languages:
mm2gv: bevel nie gevind nie
mm2gv: comandă negăsită
mm2gv: comando não encontrado
mm2gv: commande introuvable
mm2gv: command not found
mm2gv: käsku ei ole
mm2gv: không tìm thấy lệnh
mm2gv: komanda nerasta
mm2gv: Kommando nicht gefunden.
mm2gv: kommandot finns inte
mm2gv: komut yok
mm2gv: nie znaleziono polecenia
mm2gv: níor aimsíodh an t-ordú
mm2gv: no se encontró la orden
mm2gv: no s'ha trobat l'ordre
mm2gv: opdracht niet gevonden
mm2gv: parancs nem található
mm2gv: perintah tidak ditemukan
mm2gv: príkaz nenájdený
mm2gv: příkaz nenalezen
mm2gv: команда не найдена
mm2gv: командата не е открита
mm2gv: 命令找不到
mm2gv: コマンドが見つかりません