migrating ssh keys intra-machine

[shu2462]

Desire to migrate (copy) ssh keys to another op-sys on the same machine. More specifically, have Lubuntu 18.04 on partition 1. Then installed Debian 9 on partition 2 and Debian 10 on partition 3. Same computer, same hostname, same domainname, same login name, same passwords. Have copied Lubuntu /home/me/.ssh/* into /home/me/.ssh of other partitions. Desire to ssh to<>from other machines around the LAN without regard to what op-sys is active on this machine. Do not mind presenting password for login, but having to wipe the known_hosts is becoming a major bother.

Have stumbled/searched around the web on this issue but - rather surprisingly - found nothing that seems to address it. - shu

[SeijiSensei]

Usually having the same .ssh directory is all you need. Are you getting errors?

[shu2462]

Thanks for the reply, Sensei.

//charlie is the machine at issue. //bravo is my Win10 principal machine, running WSL bash.
Desired outcome is ssh from //bravo to //charlie regardless of what op-sys is running on //charlie.

booted //charlie to well established install of Lubuntu 18.04
then at //bravo:
$ rm ~/.ssh/known_hosts ............#to start clean
$ ssh charlie .............#ordinary first-time ssh procedure, no problem

boot //charlie to fresh install of Debian 9.9
[create mount point; mount Lubuntu partition; copy Lubuntu/home/rick/.ssh/* to Debian/home/rick/.ssh]

back at //bravo:
rick@BRAVO:~$ ssh charlie
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @@@@@@@@@
@ 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 a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
SHA256:BbqaAgZE1fBiMp+XgO5tlftwNIxg97pkXkN1pPikv+s .
Please contact your system administrator.
Add correct host key in /home/rick/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /home/rick/.ssh/known_hosts:1
remove with:
ssh-keygen -f "/home/rick/.ssh/known_hosts" -R "charlie"
ECDSA host key for charlie has changed and you have requested strict checking.
Host key verification failed.
rick@BRAVO:~$

To clear the error I can either
do the suggested "ssh-keygen -f ...." or simply
rm ~/.ssh/known_hosts.

[The Cog]

I think maybe the host id is in /etc/ssh. You could try copying these across, but make sure you keep the originals to restore if it doesn't work.

[shu2462]

Indeed! Fixdit!

Per usual practice, made a safety fallback copy at //charlie
$ sudo cp -r /etc/ssh /etc/ssh.af ................#(=as found)

Two config files in the new Debian /etc/ssh were different from those in the established Lubuntu partition. Those I left intact. Copied from the established Lubuntu partition to the new Debian partition
..all /etc/ssh/ssh_host*
..an /etc/ssh/ssh_import_id ............#for no password login to the Synology NAS

Done, and thank you. -shu