SSH connection problem with “Host key verification failed…” error

Question

I can connect to another Ubuntu machine in my LAN via SSH. On both of then PC's I installed openssh-server but from another Ubuntu computer I can not connect to my PC via SSH and I got this error:

"Host key verification failed..."

Answer 1

"Host key verification failed" means that the host key of the remote host was changed.

Ssh stores the host keys of the remote hosts in ~/.ssh/known_hosts. You can either edit that text file manually and remove the old key (you can see the line number in the error message), or use

ssh-keygen -R hostname

(which I learnt from the answer to Is it possible to remove a particular host key from SSH's known_hosts file?).

Answer 2

In my case, this was caused by a udev problem - there was no /dev/tty device node. The solution for me was just:

sudo mknod -m 666 /dev/tty c 5 0

Answer 3

Well, it simply because the second ubuntu requires connection by key and not password.

I suggest you use sudo dpkg-reconfigure openssh-server on your pc, and then it should work properly. It will reset the configuration for openssh and should come back to a default password authentication.

Second possibility is that there's already a key for your other ubuntu in you PC, and that it changed thus being not recognized anymore. In this case, you'll have to edit the file .ssh/authorized_keys to remove the problematic line identifying your ubuntu.

Answer 4

Also sometimes there is situation when you are working on serial console, then checking above command in verbose mode -v will show you /dev/tty does not exists, while it does.

In above case just remove /dev/tty and create a symlink of /dev/ttyS0 to /dev/tty.

As an alternative add id_rsa.pub to remote location, so password is not prompted and you get login access.

Answer 5

pico ~/.ssh/known_hosts and delete all lines, after just reconnect and you will get a new key.