I've been silently learning from all of you for a long time. So thank you in advance for that! But now I got to a point where no google search can help with this issue I'm presented. I've found some info on these links, but sadly, it doesn't address exactly what I need (or at least I'm not seeing it):



Scenario: I have a Mac computer connected to a Ubuntu server through SSH. I'm testing RSA key authentication through it, and it works right. However ONLY if the client key file name for the key is id_rsa.pub. Whenever this name changes, the ssh handshake goes:

debug1: Next authentication method: publickey
debug1: Offering public key: rsa-key-2.pub RSA SHA256:********/s explicit
debug2: we sent a publickey packet, wait for reply
debug1: Server accepts key: rsa-key-2.pub RSA SHA256:*******/s explicit
Load key "rsa-key-2.pub": invalid format
debug2: we did not send a packet, disable method
debug1: Next authentication method: password

(rsa-key-2 is my second test key, I've .backup-ed the id_rsa original ones for testing purposes. As you can see, sshd seems to see the keys though, why doesn't it accept it?)

My issue is; what if I want to have more than one key to access different Linux machines? Can't I have a key1.pub, key2.pub, etc, file so I can store different keys on my computer for my different linux servers?

Workarounds attempted: I've been tinkering with sshd_config (host end) and ssh_config on the client end, but I didn't get to make it work (always restarting sshd after any changes).

PubkeyAuthenticationis set to yes. I tried adding HostKey /etc/ssh/name of the key I want to use but that didn't work either.

Do you think there's something I can do to have several local RSA keys that work with several different Linux machines (or the same, for testing purposes)?

I hope I explained my issue properly, and most importantly, thank you in advance for any input/help.


  • You tried the ssh -i flag?
    – user535733
    Jul 12, 2020 at 19:24
  • @user535733 The -i identity_file flag is to define the private rsa (id_rsa) file to use. The .pub files should not be used directly beyond the initial setup with a given host. They are usually added to the host's ~/.ssh/authorized_keys file to enable a specific private rsa key's access. @iPodClassic Have you copied the contents of the relevant id_rsa.pub file into the remote host's ~/.ssh/authorized_keys file?
    – SHawarden
    Jul 12, 2020 at 21:41
  • @user535733 Yes. The idea is to avoid using any flags. Just the username and the domain. My question is, why does the sshd recognise the key but does not accept it when the name is not id_rsa.pub? And why does it accept it when otherwise? <br/><br/> @SHawarden: Yes sir. authorized keys file shows both keys correctly .I´ve uploaded them vía ssh-copy-id Jul 12, 2020 at 21:44
  • @iPodClassic if you want to use a non-default identity file name, then assuming the Mac client is also OpenSSH based, you either pass the private key file name on the command line with the -i switch, or create a ~/.ssh/config file with an IdentityFile entry for the target host. Please show the SSH command plus any .ssh/config that you are using on the Mac so that we can confirm that's what you are doing. Jul 12, 2020 at 22:07
  • Hello @steeldriver! How would I go tinkering with the ~/.ssh/config file? On my host machine there is no such file. I've read about that file, but wasn't really sure how to setup IdentifyFile entry. Was it supposed to be on a root level? User level? So many questions! --- (Apologies in advance for my noobity, I guess we're all been there once, so thanks for your patience!) Jul 14, 2020 at 15:05


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