Ssh Generate Key Known_hosts
Jun 22, 2012 SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone. With SSH keys, users can log into a server without a password. This tutorial explains how to generate, use, and upload an SSH Key Pair. The /etc/ssh/sshknown hosts and /.ssh/knownhosts files contain the host public keys for all known hosts. The use of the global file is optional; if it is used, it must be prepared by the administrator. The per-user file is maintained automatically. Cp /.ssh/knownhosts /.ssh/knownhosts.bak Then edit knownhosts to clear the original key, then ssh to the host using: ssh name@computer It'll add the new key automatically; then compare the two files. A program such as meld is a nice way to compare the two files. Then merge the files to make knownhosts contain both keys.
The last month, i decided to upgrade the server where Our Code World is currently hosted for a genuinely better server. As i always do, i adquired the new server and started configuring it in order to migrate the old server data. After a while, i went to the administration panel of the server in their website to remove the old root key file and i noticed that the datacenter where the server was located wasn't in america, but in France. The chosen datacenter was wrong, so i requested a new server in america. After the deployment, i installed the new operative system, but i installed the wrong version of Ubuntu (16 instead of 18.04), so i wiped once again the serverxF0x9F不. After checking finally that everything that i installed the right version of Ubuntu, i tried to access the server via SSH, for my surprise once again, i ended up with another error:
The issue is caused because you are connecting to a server where you previously were connected to, but whose RSA host changed since the last time you connected to it (i connected to the first version of the server with Ubuntu 16.04 and then tried to connected to the same server with Ubuntu 18.04 and the exception showed up). In order to prevent any security breach, you will need to remove this key from the known_hosts file of your local machine in order to connect properly.
A. Manually remove offending key
Well, deleting the known_hosts file is a valid solution as long as you don't care about having to confirm everytime that you connect to some server that the fingerprint is valid, so don't delete the known_hosts file. The easiest solution is to simply remove the line with the problem on the file, in our case the exception message warned us that the offending key is in the line #5:
So you would only need either to remove the line, using a single command like this (replace 5 with the number of your line):
And that's it. Alternatively, modify the known_hosts file using a terminal editor like nano or vim and remove the line by yourself.
B. Using ssh-agent
Alternatively, you can use the ssh-keygen tool to simply remove the offending key if you know the hostname/ip:
This should work as well to remove the warning from appearing in the terminal.
Generate ssh private key centos. O +-+The public key is now located in /home/ demo/.ssh/idrsa.pub. The private key (identification) is now located in /home/ demo/.ssh/idrsa. o + = +.
Happy coding xE2x9D歹xB8x8F!
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[donotprint][/donotprint]To regenerate keys you need to delete old files and reconfigure openssh-server. It is also safe to run following commands over remote ssh based session. Your existing session shouldn’t be interrupted.
Why regenerate new ssh server keys?
Most Linux and Unix distribution create ssh keys for you during the installation of the OpenSSH server package. But it may be useful to be able re-generate new server keys from time to time. For example, when you duplicate VM (KVM or container) which contains an installed ssh package and you need to use different keys from cloned KVM VM guest/machine.
Steps to regenerate OpenSSH host keys on Linux
Let us see all steps
Step 1 – Delete old ssh host keys
Generate Ssh Key Known_hosts
Login as the root and type the following command to delete files on your SSHD server:# /bin/rm -v /etc/ssh/ssh_host_*
Sample outputs:
Step 2 – Debian or Ubuntu Linux Regenerate OpenSSH Host Keys
Now create a new set of keys on your SSHD server, enter:# dpkg-reconfigure openssh-server
Sample output:
You just regenerated new ssh server keys. You need to restart ssh server:$ sudo systemctl restart ssh
OR$ /etc/init.d/ssh restart
Step 3 – Update all ssh client(s) known_hosts files
Finally, you need to update ~/.ssh/known_hosts files on client computers, otherwise everyone will see an error message that read as follows:
Either remove host fingerprint or update the file using vi text editor (command must be typed on client machine):$ ssh-keygen -R remote-server-name-here
Now login using the ssh command:$ ssh vivek@server1.cyberciti.biz
Conclusion
Add Ssh Key Known_hosts
You just regenerated OpenSSH Host Keys on a Debian or Ubuntu Linux using the dpkg-reconfigure command. For more info see the man page or this wiki page here:$ man dpkg-reconfigure
$ man sshd
Ssh Known Hosts Delete
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