In this Linux tutorial, you will learn how to update hostkey automatically in known hosts.
If you get below error when you try to take ssh access of Linux server.
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@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
[…].
Please contact your system administrator.
Add correct host key in /home/Linux-user/.ssh/known_hosts to get rid of this message.
Offending RSA key in /home/Linux-user/.ssh/known_hosts:287
RSA host key for […] has changed and you have requested strict checking.
Host key verification failed.
This above message is normal, this kind message you will get when you have updated your ssh-key means new key doesn’t match the old one.
You can easily resolve ssh issue with simple step
Option 1: Just edit “~/.ssh/known_hosts“ or “/home/Linux-user/.ssh/known_hosts” and delete line 287
[OR]
Option 2: Use ssh-keygen command to delete the invalid key
Eg: ssh-keygen -R “IP Address or your server hostname”
This method will tell ssh to update the host’s key which has changed and the new key needs to add/update.
–R hostname
Removes the hostname keys from a known_hosts file. To delete hashed hosts this option is very useful (see the -H option above).
Assume you want to do the same thing for several servers then follow the below method:
Script to update/add/replace single host’s key in known_hosts
SOURCE_HOST=[hostname or IP] # Remove the old key(s) from known_hosts ssh-keygen -R $SOURCE_HOST # Add the new host’s key(s) to known_hosts and hash the hostname or IP address ssh-keyscan -H $SOURCE_HOST >> ~/.ssh/known_hosts
Script to update/add/replace multiple host’s key in known_hosts
for SOURCE_HOST in `more server-ip-address-list.txt` do # Remove the old key(s) from known_hosts ssh-keygen -R $SOURCE_HOST # Add the new host’s key(s) to known_hosts and hash the hostname or IP address ssh-keyscan -H $SOURCE_HOST >> ~/.ssh/known_hosts done
This is the end tutorial, you learned how to Update Hostkey Automatically in Known Hosts.
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