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I have two servers, one of them runs Ubuntu 14, another one runs 16.04.4. I'm trying to log in via ssh (Windows, Putty + Pageant) as a simple user, not as root. /etc/ssh/sshd_config files are identical on both machines, as well as ~/.ssh/authorized_keys and its permissions (700 to ~/.ssh, 600 to ~/.ssh/authorized_keys). Password authorization works ok.

Login to Ubuntu 14 works as charm, that to Ubuntu 16 doesn't. What could be the reason of this problem? Smth was changed in the policies in Ubuntu 16?

  • Do you have openssh-server running on the 16.04? By default (if desktop) only the client is installed; so you must install & enable on both? Maybe you only did it on Ubuntu 14.04? – guiverc Jul 19 '18 at 10:59
  • @guiverc, yes, it's a usual server, it runs sshd of course, otherwise I couldn't reach the server at all – George Hazan Jul 19 '18 at 11:31
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I had a similar problem today -- been using Windows, Putty and Pageant to auto login to my Ubuntu 14.04 server for years. But when I upgraded to Ubuntu 18.04, it stopped working.

Checking /var/log/auth.log, I found the following error:

sshd[30093]: userauth_pubkey: key type ssh-dss not in PubkeyAcceptedKeyTypes [preauth]

Googling that error message led me to the fix on this site: http://asystemengineersnotebook.blogspot.com/2017/09/fixing-key-type-ssh-dss-not-in.html

The fix for this is adding the following line /etc/ssh/sshd_config file and restarting the ssh service:

PubkeyAcceptedKeyTypes=+ssh-dss

This solved my problem.

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