FTP Server - Red Hat Linux

FTP in Linux

Introduction to FTP 

The File Transfer Protocol (FTP) is used as one of the most common means of copying files between servers over the Internet.

Regular FTP
The VSFTP allows Linux users to copy files to and from their home directories with an FTP client.

Anonymous FTP
Anonymous FTP a username of ‘anonymous’ and your email address for the password.
Once logged in to a FTP server, you automatically have access to only the default anonymous FTP directory

FTP Overview

FTP relies on a pair of TCP ports to get the job done. It operates in two connection channels as I'll explain:

FTP Control Channel, TCP Port 21: All commands you send and the ftp server's responses to those commands will go over the control connection, but any data sent back (such as "ls" directory lists or actual file data in either direction) will go over the data connection.

FTP Data Channel, TCP Port 20: This port is used for all subsequent data transfers between the client and server.

In addition to these channels, there are several varieties of FTP.

Types of FTP

From a networking perspective, the two main types of FTP are active and passive. In active FTP, the FTP server initiates a data transfer connection back to the client. For passive FTP, the connection is initiated from the FTP client

1. Active FTP
2. Passive FTP

Start VSFTP

Use the ‘chkconfig’ command to configure VSFTP to start at boot:
chkconfig vsftpd on

Use ‘service vsftpd’ to start,stop, and restart VSFTP after booting:
service vsftpd start
service vsftpd stop
service vsftpd restart \

Configuration file: /etc/vsftpd/vsftpd.conf

Anonymous FTP settings

Before going to change vsftpd.conf, remember to make a backup:
cp vsftpd.conf vsftpd.conf.bak

anonymous_enable=YES
Allow Anonymous

anon_upload_enable=YES
Allow Anonymous upload

anon_mkdir_write_enable=YES
Allow Anonymous upload to create directory

no_anon_password=YES
Do not ask password for anonymous login

anon_max_rate=30000
Limit the transfer rate of anonymous, e.g. 30000 = 30k byte per second

anon_root=/data/directory
Directory for anonymous is ‘/var/ftp’

Local users’ settings 

local_enable=YES
Allow Linux users to use VSFTPD

chroot_list_enable=YES
VSFTPD will use a file to limit some users to change their home directories after login

chroot_list_file=/etc/vsftpd/chroot_list
A text file which contain a list of Linux usernames.
These users will limit to their home directories

userlist_deny=YES
VSFTPD will use a file to reject some users.

userlist_file=/etc/vsftpd/user_list
A text file which contain a list of Linux usernames which DO NOT allow to use VSFTP.

local_max_rate=30000
Limit the transfer rate of local user, e.g. 30000 = 30k byte per second

Other Settings 

max_clients=10
Limiting the maximum number of client connections

max_per_ip=1
Limiting the number of connections by same IP address

 idle_session_timeout=600
Disconnect the idle connection after 600 seconds.

xferlog_enable=YES
Record all the file transfer records.

xferlog_file=/var/log/vsftpd.log
Filename and directory of log file.

Limit the access on hosts 

FTP server usually can use tcp_wrappers to allow or deny a host’s access.
 Add this statement to vsftpd.conf:
tcp_wrappers = yes
Under /etc, create a new file hosts.deny:
vsftpd : 192.168.1.0/24 192.168.0.2
vsftpd : .vtc.edu.hk alan.ict.edu.hk

If you want to allow a specific host, create a hosts.allow with same format.
 Power of hosts.allow > hosts.deny

Step by step

1. Package Name: vsftpd
2. Document Root: /var/ftp/pub/
3. Configuration File: /etc/vsftpd/vsftpd.conf
4. Comds To Be Exec on Terminal:

a. #yum install vsftpd* -y
b. #service vsftpd restart;
    # chkconfig vsftpd on

[N.B. At this stage any existing user can access the ftp from their browser using the ftp host IP e,g ftp://192.168.0.1.They can download anything that is placed inside the document root /var/ftp/pub.To restrict ftp use follow the steps mentioned below.]

c.
#vim /etc/vsftpd/vsftpd.conf
Edit following fields:
Anonymous_enable=NO
Chroot_list_enable=YES
Save and exit the configuration file.

d.
#service vsftpd restart;
#chkconfig vsftpd on