Telnet will only work if you enable the telnet service on the Linux server. Most modern *nix servers turn off telnet and use ssh instead, because of security issues with telnet (for one thing, the password is sent in plaintext). Hence, you can do one of two things:
1. Turn on telnet on the linux server and then use the telnet component to connect to it (not recommended).
2. Find an ssh component for Delphi. There are several available, but most are not free.
3. Download a command line ssh tool for Windows, such as Putty and execute this from your Delphi program with WinExec or ShellExecute and pass the command string to it.－－－这个办法不知道是否可行。。。。也许需要putty能支持特定的某种自动方式？？

There is actually a fourth method and this is what I used around 6 years ago. You can write a quick daemon on the Linux end (in perl, python, C or whatever) that listens on a specific port for certain commands to come in. Then, all you have to do is use a socket component to connect to your daemon and send it the specific magic command to tar up the file. To make it even more secure, your daemon should only accept connections from a specific IP address.