mvn: 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/maven2/bin/mvn - from package: maven2
/usr/share/maven/bin/mvn - from package: maven

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

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