debian vsftpd part1

debain 11
vsftpd = ftp server
ftp (file tranfer protocal) : I used ftp in 1990.
sudo apt install vsftpd


- systemctl (list and control systems running on Linux using systemd)

passive mode:
Passive FTP Overview
Passive FTP is an FTP mode that can be requested by a client
to alleviate the issues caused by client-side firewalls.
Both the server and the client must support passive
FTP for this process to work.
When passive FTP is used, the client will initiate the connection to the server. This process is effective because most firewalls allow inbound traffic from sessions initiated by the client. A passive FTP connection follows the following process:
The client sends the PASV command to an FTP server on port 21.
The source port is a random, high-numbered port.
The destination port is 21.

The server responds with the PORT command.
The port command specifies a random,
high-numbered (ephemeral) port that the client can connect to.

The client initiates a connection to the server on this ephemeral port.

The server responds with an ACK.
The FTP session has now been established

chroot:
A chroot (short for change root) is a Unix/Linux operation that changes
the apparent root directory to the one specified by the user.
Any process you run after a chroot operation only has access
to the newly defined root directory and its subdirectories.