Debian etch (40r5) upgrade source and add public key

1. Add servers from Shanghai Jiao Tong University

First back up the sources. list file,

CP/etc/APT/sources. LIST/etc/APT/sources. List. Bak

Edit the sources. list file,

VI/etc/APT/sources. List

Add the source,

Deb http://ftp.sjtu.edu.cn/debian etch main contrib non-free

Save and exit, update,

Apt-Get update

2. When you add a public key to use the above source, the following problems may occur:

W: GPG error: http://ftp.sjtu.edu.cn etch release: The following signature cannot be verified because there is no public key: no_pubkey 9aa38dcd55be302b
W: You may need to run apt-Get update to solve these problems.

However, the problem cannot be solved through apt-Get update. The online search method is as follows:

Download key:
GPG -- keyserver subkeys.pgp.net -- Recv 9aa38dcd55be302b (Note: The public key here may be different from yours)
Import key:
GPG -- export -- armor 9aa38dcd55be302b | sudo apt-key add-

3. Debian is successfully installed, and the font is almost beautified. The above figure is shown...