FTP file transfer protocol

transmission mode

FTP Two modes are supported ：Standard (PORT The way , Active way ),Passive (PASV, Passive way ).

Port Pattern

FTP Client first and server TCP 21 Port establish connection , Used to send commands , When the client needs to receive data, it will send it on this channel PORT command .PORT The command contains what port the client uses to receive data . When transmitting data , Server side through their own TCP 20 The port is connected to the specified port of the client to send data .FTP server A new connection must be established with the client to transmit data .

Passive Pattern

Establish control channels and Standard Similar model , But after establishing the connection, send Pasv command . Server received Pasv After the command , Open a temporary port （ The port number is greater than 1023 Less than 65535） And notify the client of the request to transmit data on this port , Client connection FTP Server this port , then FTP The server will transmit data through this port .

quite a lot Firewalls are not allowed to accept externally initiated connections when they are set , So many are located behind the firewall or intranet FTP Server does not support PASV Pattern , Because the client cannot open through the firewall FTP The high-end port of the server ; Many intranet clients cannot use PORT Mode login FTP The server , Because from the server TCP 20 Unable to establish a new connection with the client of the internal network , Make it impossible to work .

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To configure  

install

yum install -y vsftpd

  Turn off firewall

systemctl stop firewalld
setenforce 0

Set up service startup

systemctl enable vsftpd
# Boot up 
systemctl start vsftpd
# Turn on vsftpd
systemctl status vsftpd
# see vsftpd The state of 

  Modify the configuration file （ Anonymous access ）

vim  /etc/vsftpd/vsftpd.conf

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test

stay /var/ftp/pub/ Next create a txt text file , stay windows On this PC , Input ftp The address of the server

  success ！

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Account password login FTP

Get into /etc/vsftpd/vsftpd.conf Set the configuration file

vim /etc/vsftpd/vsftpd.conf

  Get into /etc/vsftpd/chroot_list Add the user name with restricted login

vim /etc/vsftpd/chroot_list
 
paul    # Login username 

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Configuration file blacklist White list

/etc/vsftpd/user_list The default is blacklist , Get rid of if userlist_dent=NO Notes , Open the white list , Only the following users can log in , We join users quota To the blacklist .

echo  quota  >>  /etc/vsftpd/user_list

# vsftpd userlist
# If userlist_deny=NO, only allow users in this file
# If userlist_deny=YES (default), never allow users in this file, and
# do not even prompt for a password.
# Note that the default vsftpd pam config also checks /etc/vsftpd/ftpusers
# for users that are denied.
root
bin
daemon
adm
lp
sync
shutdown
halt
mail
news
uucp
operator
games
nobody
quota

quota The user is forbidden to log in

stay /etc/vsftpd/vsftpd.conf Middle configuration , After restarting the service quota Login successful

vim /etc/vsftpd/vsftpd.conf
userlist_enable=YES
userlist_deny=NO