viva: command not found

Have You tried accessing the binary with the full path?

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/viva - from package: viva

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