Solution to slow remote logon using SSH in Linux

Article title: Solution to slow remote logon through SSH in Linux. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

The ssh logon to the server (Linux) is slow for about 15 seconds, but the ping is fast and the load on the server after logon is also very low. This small problem has not attracted attention. today, when the leader logged on, he found this problem and gave the cause and solution, which is recorded here:

There is a file/etc/nsswitch. conf on the target server, which contains the following line:

Hosts: files dns

This line indicates the domain name resolution order of the Accessed host. it is to first access the file, that is, the/etc/hosts file. if the hosts does not record the domain name, it will access dns, for domain name resolution, if the dns cannot be accessed, it will wait for the access timeout to return, so the wait time is relatively long.

If this line is blocked, can it achieve the same effect? Yes, but if the host needs to access other servers through the domain name, it will certainly not be accessible, so this line should be retained. This problem also reminds us of some side effects of dns unavailability.