sending authorized_keys to localhost from an account being created with adduser --disabled-password [was] Re: Need a tutorial

[Stephan Beck <sbeck@secure.mailbox.org>]

Hi

tomas@tuxteam.de:
> On Thu, Sep 22, 2016 at 03:35:00PM +0000, Stephan Beck wrote:
> 
> 
>> tomas@tuxteam.de:
> 
> [mumble]
> 
>>> This is the bird's view. Ask if you get stuck.
> 
> 
>> Sorry, Tomas, it's not Gene, it's me who has a special question
> 
> No need to be sorry :-)

Fine! :-)
> 
> But I see you found a solution and other chimed in with sage advice.
> 

Well, I have another one :-), a question, not a solution yet.


I have created a new user account with
adduser --disabled-password
What do I want to do?
I'd like to login to this account "test" from my normal user account by
ssh via pubkey authentication. My (normal) user account has its keys
generated and properly deposited on localhost. I logged into the account
"test" via su - test, creating a keypair. Fine.

How do I get this public key onto localhost?
I mean, I can create an authorized_keys file manually, copying the
public key into this authorized_keys file, but it's still in the user's
directory where it has been generated, it needs to be sent (or get
somehow) to localhost.

I have tried:
test@mymachine cat .ssh/id_rsa.pub | ssh localhost 'cat >>
.ssh/authorized_keys'

But it's asking me a password. There is none.
If I disable Password Authentication in sshd_config, and then try to
send it to localhost, it fails with something like "denied access
publickey required". No mystery at all, because this very public key is
being sent to localhost in this very moment and can't be used in the
same act for authentication purposes.

I've been reading a bunch of related docs in the man pages, debian wiki,
in the exquisite and very readable Debian Administrator's Handbook by
Raphael Mas and Raphaël Hertzog, and other linux ssh documentation. I
can't find my specific use case and I'm stuck.

Any hints (also from other people) welcome.

Stephan

on Debian-Jessie