How do I regenerate OpenSSH sshd server host keys stored in /etc/ssh/ssh_host_* files? Can I safely regenerate ssh host keys using remote ssh session as my existing ssh connections shouldn’t be interrupted on Debian or Ubuntu Linux? How do I regenerate new ssh server keys? How to regenerate new host keys on a Debian or Ubuntu Linux?

How to regenerate new ssh server keys This is an unusual topic since most distribution create these keys for you during the installation of the OpenSSH server package. But it may be useful to be able generate new server keys from time to time, this happen to me when I duplicate Virtual Private Server which contains an installed ssh package. When you generate key pairs, ssh-keygen showns you the key fingerprint. When you connect to a host, for which you don't have the public key in your knownhosts, ssh shows you the fingerprint for that host. Verify that both fingerprints are identical. If they are type 'yes' (the full word is required) to add the key to your knownhosts.

[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?

Indigo renderer licence key generator. 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

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Step 1 – Delete old ssh host keys

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:

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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

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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

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How do I create a host key file to use with my applications as I can not use system defined /etc/ssh/ssh_host_rsa_key for non-root account under Linux / Unix / Apple OS X / *BSD operating systems?
You need to use a command called ssh-keygen. This command generates, manages and converts authentication keys for ssh. It can create RSA keys for use by SSH protocol version 1 and RSA or DSA keys for use by SSH protocol version 2. he type of key to be generated is specified with the -t option. If invoked without any arguments, ssh-keygen will generate an RSA key for use in SSH protocol 2 connections. Extensis portfolio browser mac download. The -f option specifies the filename of the key file.

Why create a new host key files?

You may need a new key file:

1. Your system is compromised.
2. Your keys are stolen.
3. You forgotten the passphrase.
4. Your application need a new host key.
5. You can not read the default system key files stored in /etc/ssh/ directory but your non-root application needs key.
6. You got an error message which read as “Could not load host key: /etc/ssh/ssh_host_key*”.

ssh-keygen Syntax

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The syntax is:

Example

Create a host key file in your $HOME/.ssh/myapp as follows. First, create a directory to store your host key file, enter:
$ mkdir -p $HOME/.ssh/myapp
To create a host RSAv2 key file, run:
$ ssh-keygen -t rsa -f $HOME/.ssh/myapp/rsa_key_file
Sample outputs:

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Type the following commands to verify the keys:
$ ls -l $HOME/.ssh/myapp/
Sample outputs:

You can now use keys with your app:
$ mycool-app -key $HOME/.ssh/myapp/rsa_key_file -d

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