vagrant: 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/vagrant - from package: vagrant

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

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