r2agent: 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/r2agent - from package: radare2

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

Error in other languages:
r2agent: bevel nie gevind nie
r2agent: comandă negăsită
r2agent: comando não encontrado
r2agent: commande introuvable
r2agent: command not found
r2agent: käsku ei ole
r2agent: không tìm thấy lệnh
r2agent: komanda nerasta
r2agent: Kommando nicht gefunden.
r2agent: kommandot finns inte
r2agent: komut yok
r2agent: nie znaleziono polecenia
r2agent: níor aimsíodh an t-ordú
r2agent: no se encontró la orden
r2agent: no s'ha trobat l'ordre
r2agent: opdracht niet gevonden
r2agent: parancs nem található
r2agent: perintah tidak ditemukan
r2agent: príkaz nenájdený
r2agent: příkaz nenalezen
r2agent: команда не найдена
r2agent: командата не е открита
r2agent: 命令找不到
r2agent: コマンドが見つかりません