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active mode
Active mode is the original method used by the `FTP` protocol for transferring data to the client application. When an active mode data transfer is initiated by the `FTP` client, the server opens a connection from port 20 on the server to the `IP` address and a random, unprivileged port (greater than 1024) specified by the client. This arrangement means that the client machine must be allowed to accept connections over any port above 1024. With the growth of insecure networks, such as the Internet, the use of firewalls to protect client machines is now prevalent. Because these client-side firewalls often deny incoming connections from active mode `FTP` servers, passive mode was devised.
Additional Resources
All configuration of [command]#vsftpd# is handled by its configuration file, `/etc/vsftpd/vsftpd.conf`. Each directive is on its own line within the file and follows the following format:
*All operations requiring elevated privileges are handled by a small parent process* — Much like the Apache `HTTP` Server, [command]#vsftpd# launches unprivileged child processes to handle incoming connections. This allows the privileged, parent process to be as small as possible and handle relatively few tasks.
*All requests from unprivileged child processes are distrusted by the parent process* — Communication with child processes are received over a socket, and the validity of any information from child processes is checked before being acted on.
Anonymous logins are prevented unless the password provided is listed in [command]#/etc/vsftpd/email_passwords#. The file format is one password per line, with no trailing white spaces.
Anonymous User Options
Avoid enabling the chroot_local_user option
Avoid enabling the pasv_promiscuous option
By default [command]#vsftpd# displays its standard banner.
By default, `firewalld` blocks incoming FTP connections. To allow FTP connections, as `root` type:
By default, the [command]#vsftpd# service does *not* start automatically at boot time. To configure the [command]#vsftpd# service to start at boot time, use a service manager such as [command]#systemctl#. See xref:infrastructure-services/Services_and_Daemons.adoc#ch-Services_and_Daemons[Services and Daemons] for more information on how to configure services in {MAJOROS}.
[command]#accept_timeout# — Specifies the amount of time for a client using passive mode to establish a connection.
[command]#anon_max_rate# — Specifies the maximum data transfer rate for anonymous users in bytes per second.
[command]#anon_mkdir_write_enable# — When enabled in conjunction with the [command]#write_enable# directive, anonymous users are allowed to create new directories within a parent directory which has write permissions.
[command]#anon_root# — Specifies the directory [command]#vsftpd# changes to after an anonymous user logs in.
[command]#anon_upload_enable# — When enabled in conjunction with the [command]#write_enable# directive, anonymous users are allowed to upload files within a parent directory which has write permissions.
[command]#anon_world_readable_only# — When enabled, anonymous users are only allowed to download world-readable files.