How to establish ssh key pair when Host key verification failed

Question

I have set up ssh key pairs between my desktop and two servers  and from the servers to my desktop  but after reinstalling the OS on my desktop  I can t re-establish the key-pair going into my desktop by this  mkdir    ssh chmod 700    ssh ssh-keygen -t  ssh-copy-id username server  I get the following error   names in italics changed to protect the innocent My desktop is Ubuntu  and I can t find the answer  here                                                                    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 the RSA host key has just been changed  The fingerprint for the RSA key sent by the remote host is ab cd ef gh Please contact your system administrator  Add correct host key in  home user  ssh known hosts to get rid of this message  Offending key in  home user  ssh known hosts 1 RSA host key for user server has changed and you have requested strict checking  Host key verification failed

User · Answer

This issue arises when the host key is expired or changed. you can remove the keys that host is using and try to ssh again, so that you are adding new key that is known to both client and server.

You can check the keys associated with your hosts with cat /.ssh/known_hosts . Now, You can remove the hosts keys manually or using the ssh-keygen option. You can do either of the following option.

Manual removal of keys

vim /.ssh/known_hosts

delete the key that is associated with your host.

Remove key using ssh-keygen

ssh-keygen -R your_host_or_host_ip

This will remove your key associated with the host.

Now, you can ssh to your host as usual and you will be asked if you want to continue to this host. Once your enter yes, this host will be added to your/.ssh/known_hosts with updated key. By now, you should be your host.

User · Answer

When you try to connect your remote server with ssh       ssh username ip address   then the error raise  to solve it       ssh-keygen -f   home local username  ssh known hosts  -R  ip address

User · Answer

First you should remove existing key  SSH keys in most of Linux-based OS will be saved this file   root  ssh known hosts   so in order to remove the key related to host the following command will be used   ssh-keygen -f   root  ssh known hosts  -R  Hostname   Regards K1

User · Answer

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

User · Answer

Most likely  the remote host ip or ip alias is not in the    ssh known hosts file  You can use the following command to add the host name to known hosts file    ssh-keyscan -H -t rsa ip or ipalias   gt  gt     ssh known hosts  Also  I have generated the following script to check if the particular ip or ipalias is in the know hosts file      bin bash  Jason Xiong  Dec 2013      The ip or ipalias stored in known hosts file is hashed and      is not human readable This script check if the supplied ip       or ipalias exists in    ssh known hosts file  if          2     then    echo  Usage    search known hosts -i ip or ipalias     exit  fi ip or alias  2  known host file  home user  ssh known hosts entry 1   cat  known host file   while read -r line do   if    -z   line      then     continue    fi      hash type   echo  line   sed -e  s     g   awk   print  1        key   echo  line   sed -e  s     g   awk   print  2       stored value   echo  line   sed -e  s     g   awk   print  3        hex key   echo  key   base64 -d   xxd -p      if      hash type   1     then            gen value   echo -n  ip or alias   openssl sha1 -mac HMAC            -macopt hexkey  hex key   cut -c 10-49   xxd -r -p   base64             if     gen value    stored value     then        echo  gen value         echo  Found match in known hosts file   entry   entry             fi   else      echo  unknown hash type    fi   entry    entry   1    done

User · Answer

Task Passwordless authentication for suer   Error   Host key verification failed   Source  10 13 1 11 Target   10 13 1 35  Temporary workaround     user server    ssh user 10 13 1 35 The authenticity of host  10 13 1 35  10 13 1 35   can t be established  RSA key fingerprint is b8 ba 30 46 a9 ab 70 12 1a f2 f1 61 69 73 0a 19  Are you sure you want to continue connecting  yes no   yes Warning  Permanently added  10 13 1 35   RSA  to the list of known hosts   Try to authenticate user again   it will work

User · Answer

If you re sure the server is correct  sed -i 1d    ssh known hosts will delete line 1 of your local    ssh known hosts   The new correct key will be added to the file the next time you connect

User · Answer

rm -f  home user  ssh known hosts   or open it up and delete the entry for the offending ip hostname   P S  It tells you exactly this in the error message you posted

User · Answer

Its means your remote host key was changed  May be host password change    Your terminal suggested to execute this command as root user    ssh-keygen -f   root  ssh known hosts  -R  www website net  4231   You have to remove that host name from hosts list on your pc server  Copy that suggested command and execute as a root user     sudo su                                                               Login as a root user    ssh-keygen -f   root  ssh known hosts  -R  www website net  4231      Terminal suggested command execute here Host  www website net  4231 found  line 16 type ECDSA  root  ssh known hosts updated  Original contents retained as  root  ssh known hosts old    exit                                                                  Exist from root user    sudo ssh root www website net -p 4231                                 Try again   I Hope this works

User · Answer

ssh-keygen -R hostname   This deletes the offending key from the known hosts  The man page entry reads      -R hostname Removes all keys belonging to hostname from a known hosts file  This option is useful to delete hashed hosts  see the -H option   above

User · Answer

Step1  Bhargava ssh        ssh-keygen -R 199 95 30 220   step2  Bhargava ssh        ssh-copy-id hostname 199 95 30 220             Enter the the password            step3  Bhargava  ssh        ssh hostname 199 95 30 220   Welcome to Ubuntu 14 04 3 LTS  GNU Linux 3 13 0-68-generic x86 64    Documentation  https   help ubuntu com  Ubuntu 14 04 3 LTS server   228839 ip   199 95 30 220 hostname   qt example com System information as of Thu Mar 24 02 13 43 EDT 2016 System load  0 67 Processes  321 Usage of  home  5 1  of 497 80GB Users logged in  0 Memory usage  53  IP address for eth0  199 95 30 220 Swap usage  16  IP address for docker0  172 17 0 1 Graph this data and manage this system at  https   landscape canonical com  Last login  Wed Mar 23 02 07 29 2016 from 103 200 41 50   hostname qt

[ubuntu] How to establish ssh key pair when "Host key verification failed"

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