dvbv5-scan: 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/dvbv5-scan - from package: v4l-utils

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

On Debian possible default full paths are:

/usr/bin/dvbv5-scan - from package: dvb-tools

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

Error in other languages:
dvbv5-scan: bevel nie gevind nie
dvbv5-scan: comandă negăsită
dvbv5-scan: comando não encontrado
dvbv5-scan: commande introuvable
dvbv5-scan: command not found
dvbv5-scan: käsku ei ole
dvbv5-scan: không tìm thấy lệnh
dvbv5-scan: komanda nerasta
dvbv5-scan: Kommando nicht gefunden.
dvbv5-scan: kommandot finns inte
dvbv5-scan: komut yok
dvbv5-scan: nie znaleziono polecenia
dvbv5-scan: níor aimsíodh an t-ordú
dvbv5-scan: no se encontró la orden
dvbv5-scan: no s'ha trobat l'ordre
dvbv5-scan: opdracht niet gevonden
dvbv5-scan: parancs nem található
dvbv5-scan: perintah tidak ditemukan
dvbv5-scan: príkaz nenájdený
dvbv5-scan: příkaz nenalezen
dvbv5-scan: команда не найдена
dvbv5-scan: командата не е открита
dvbv5-scan: 命令找不到
dvbv5-scan: コマンドが見つかりません