GitLab clone over SSH not working on 'new machine' - ssh

Question

I'm having issues cloning a repository on a new machine. While git clone over SSH works perfectly fine on a machine which I had already setup (a while ago), I've now added my public key in the GitLab GUI and try git clone git#, but without success. The fact that it works on my other machine, suggests a client-side issue to me. What I'm trying:
ssh -vT git#<DOMAIN_NAME>.de
OpenSSH_7.2p2 Ubuntu-4ubuntu2.4, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: Connecting to <DOMAIN_NAME>.de [141.89.97.171] port 22.
debug1: Connection established.
debug1: identity file <HOME_DIR>/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file <HOME_DIR>/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file <HOME_DIR>/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file <HOME_DIR>/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file <HOME_DIR>/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file <HOME_DIR>/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file <HOME_DIR>/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file <HOME_DIR>/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1 Debian-5ubuntu1.10
debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1.10 pat OpenSSH_5* compat 0x0c000000
debug1: Authenticating to <DOMAIN_NAME>.de:22 as 'git'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: ecdh-sha2-nistp256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: aes128-ctr MAC: umac-64#openssh.com compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: umac-64#openssh.com compression: none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:QUDzLMIelWfaGrqQjj9O7DLHHeW/1mG/+b8fYvXck34
debug1: Host '<DOMAIN_NAME>.de' is known and matches the ECDSA host key.
debug1: Found key in <HOME_DIR>/.ssh/known_hosts:1
debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS received
debug1: pubkey_prepare: ssh_get_authentication_socket: Permission denied
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering RSA public key: <HOME_DIR>/.ssh/id_rsa
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: <HOME_DIR>/.ssh/id_dsa
debug1: Trying private key: <HOME_DIR>/.ssh/id_ecdsa
debug1: Trying private key: <HOME_DIR>/.ssh/id_ed25519
debug1: Next authentication method: password
git#<DOMAIN_NAME>.de's password:
I checked the public key in the GitLab GUI with the one in my .ssh/id_rsa.pub (they match), so I expect it to work without this password prompt. I've checked several SO posts (ssh clone not working with github) (I'm aware that gitlab and github are two different beasts), gitlab issue pages, etc., but haven't found a solution yet. Again; what particularly bothers me is that this is not working for an 'unseen' machine, and works for others, suggesting something on the client side. Still, I have restarted and reconfigured gitlab (gitlab-ctl restart and gitlab-ctl reconfigure) as well on the server, both before and after adding my new public key, but that didn't help either.
Any thoughts?

Answer 1

For future reference/anyone who runs into the same problem; I've fixed it with a gitlab-rake gitlab:shell:setup on the server that is hosting gitlab. No restart (of gitlab), reconfigure or re-generating/copying of the key file needed.