VsFTP Interview Questions

Q) Active and Passive FTP?

Active and Passive FTP are two modes of connection that FTP runs in. FTP uses two channels between client and server, the command channel and the data channel.

Typically command channel is on port no 21 and data channel is on port no 20. The command channel handles commands and responses, the data channel handles actually transferring files.

The difference between active and passive mode lies in whether server or client initiate the data connection.

In active mode, server initiate data connection with the client after the client has established a connection on command channel.

In passive mode, the client establishes the data connection with the server. 

Reference Link: stackoverflow.com

Active FTP:

1. The client connects to FTP server by establishing FTP control connection on port no 21 of the server.

2. Whenever the client requests data over the control connection the server initiates data transfer connection back to the client.

3. The source port for this data transfer connection is always on port no 20 of the server and destination port is the higher port (greater than 1024) on the client side.

4. Active mode is more secure for the server as it does not require an insecure port to be open at server end because it’s the server that initiates the data connection with the client side.

Passive FTP:

1. The client connects to FTP server by establishing FTP control connection on port no 21 of the server.

2. Whenever the client requests data over the control connection the client initiates data transfer connection back to the server.

3. The source port for this data transfer connection is always on the higher port on the client side and destination port is the higher port on the server side.

Reference Link: http://www.slacksite.com/other/ftp.html

Q) Restrict user to their home directory?

Reference Link: https://rravikumar.wordpress.com/2012/02/08/restrict-vsftp/