burp: 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/sbin/burp - from package: burp-client

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

On Debian possible default full paths are:

/usr/sbin/burp - from package: burp

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

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