Ubuntu – How to reset SSH configuration on the PC

opensshsshUbuntu

How can I reset all the SSH settings, so that it worked as after fresh install? (I may delete the keys, they're not needed anymore.)

In Ubuntu 9.10, after a certain moment I started getting "Host key verification error" on every SSH server! This doesn't happen if I boot U9.10 from a USB stick.

culebron@culebron:~/.ssh$ ssh culebron@217.******
Host key verification failed.
culebron@culebron:~/.ssh$

~/.ssh/known_hosts doesn't exist (I must have removed it by an advice to "clean" known hosts list), yet SSH doesn't ask me, as earlier, if I want to add a host or not, just "Host key verification failed" every time.

Best Answer

Backup ~/.ssh on your computer, rm -rf ~/.ssh, try again. If that works, figure out which part of your old ~/.ssh was causing the problem (if you care).

Related Solutions

Macos – /.ssh/known_hosts file does not exist? (Mac)

The article Failed to add the host to the list of known hosts has this advice :

Check directory permissions

The ssh client needs to be able to write to files in the .ssh directory :

ls -ld ~/.ssh

If the permissions aren't correct then run this to fix them:

chmod 0700 ~/.ssh

Check file permissions

Check if the files in the .ssh directory have read-write permissions :

ls -l ~/.ssh

If they don't, run :

chmod 0600 ~/.ssh/*

Remove ACL flags

If the ssh client still cannot write to the folder, one needs to clear the ACL flags :

chmod -R -a# 0 ~/.ssh

Copy ssh keys from one server to another server

As Ethabell mentioned, you can copy over the current host keys to the new server.

You can find your host keys by opening your sshd_config file (On my Ubuntu 12.04 box its /etc/ssh/sshd_config). In the config file look for the HostKey entries. These entries will tell you where the host key files are located. You should be able to copy these files to the new server and update the new server's sshd_config to point to the copied keys (or just overwrite the files that already exist on the new server).

Also, note this section from the sshd_config man page, specifically the part about permissions:

Specifies a file containing a private host key used by SSH. The default is /etc/ssh/ssh_host_key for protocol version 1, and /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_ecdsa_key and /etc/ssh/ssh_host_rsa_key for protocol version 2. Note that sshd(8) will refuse to use a file if it is group/world-accessible. It is possible to have multiple host key files. “rsa1” keys are used for version 1 and “dsa”, “ecdsa” or “rsa” are used for version 2 of the SSH protocol.

Best Answer

Related Solutions

Macos – /.ssh/known_hosts file does not exist? (Mac)

Copy ssh keys from one server to another server

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