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I followed the following steps from https://docs.ceph.com/en/latest/cephadm/install/ to setup a ceph cluster on Centos 8.1

curl --silent --remote-name --location https://github.com/ceph/ceph/raw/octopus/src/cephadm/cephadm chmod +x cephadm ./cephadm add-repo --release octopus ./cephadm install

After the above command I found out that ceph requires either docker or podman to run. So I installed the community version of docker from https://docs.docker.com/engine/install/centos/ and continued the steps below.

./cephadm install mkdir -p /etc/ceph cephadm bootstrap --mon-ip *ip_of_the_current_machine (host1)* cephadm install ceph-common ssh-copy-id -f -i /etc/ceph/ceph.pub root@host2* ceph orch host add host2

The above command fails with the error

[root@host1 home]# ceph orch host add host2 INFO:cephadm:Inferring fsid 12345678-2345-6789-1011-000129110013 INFO:cephadm:Inferring config /var/lib/ceph/12345678-2345-6789-1011-000129110013/mon.host1/config INFO:cephadm:Using recent ceph image ceph/ceph:v15 Error EINVAL: Failed to connect to host2 (host2). Check that the host is reachable and accepts connections using the cephadm SSH key you may want to run: > ceph cephadm get-ssh-config > ssh_config > ceph config-key get mgr/cephadm/ssh_identity_key > key > ssh -F ssh_config -i key root@host2

I am able to login to host2 using the above steps. Could someone please tell if I am doing something wrong. How do I solve this problem.

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  • Hello everyone, I would like to point out that any comments are welcome. If you plan to downvote this question, please make sure to add a comment so that helps me put this question in a better way. Commented Nov 11, 2020 at 9:51
  • It's unclear to me where your setup could be wrong. I just deployed a cluster with cephadm bootstrap and added a second node successfully. Did you install cephadm on the second node, too? Did you check if your ssh connection worked passwordless? I should mention that I installed cephadm directly from the repository (openSUSE Leap 15.2), not with the github script. But it worked flawlessly for me. Commented Nov 12, 2020 at 13:05
  • Also does the name resolution work? At least having both hosts in /etc/hosts should be sufficient. Commented Nov 12, 2020 at 14:33

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So after days of debugging I figured out that python3 was missing on the node I wanted to add. All I had to do was check the last few logs using the command.

ceph log last cephadm

This gave the following log messages.

Traceback (most recent call last): File "/usr/share/ceph/mgr/cephadm/module.py", line 1036, in _remote_connection raise execnet.gateway_bootstrap.HostNotFound(msg) execnet.gateway_bootstrap.HostNotFound: Can't communicate with remote host `host2`, possibly because python3 is not installed there: cannot send (already closed?) The above exception was the direct cause of the following exception: Traceback (most recent call last): File "/usr/share/ceph/mgr/orchestrator/_interface.py", line 295, in _finalize next_result = self._on_complete(self._value) File "/usr/share/ceph/mgr/cephadm/module.py", line 103, in <lambda> return CephadmCompletion(on_complete=lambda _: f(*args, **kwargs)) File "/usr/share/ceph/mgr/cephadm/module.py", line 1201, in add_host return self._add_host(spec) File "/usr/share/ceph/mgr/cephadm/module.py", line 1187, in _add_host error_ok=True, no_fsid=True) File "/usr/share/ceph/mgr/cephadm/module.py", line 1104, in _run_cephadm with self._remote_connection(host, addr) as tpl: File "/lib64/python3.6/contextlib.py", line 81, in __enter__ return next(self.gen) File "/usr/share/ceph/mgr/cephadm/module.py", line 1055, in _remote_connection raise OrchestratorError(msg) from e orchestrator._interface.OrchestratorError: Failed to connect to host2 (host2). Check that the host is reachable and accepts connections using the cephadm SSH key

Next to add the node I ran.

ceph orch host add host2 ip_address
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I've faced with the same issue but my top error message was

2021-01-13T15:21:13.071913+0000 mgr.ha1.qzzjzw (mgr.18492) 167366 : cephadm [ERR] _Promise failed Traceback (most recent call last): File "/lib/python3.6/site-packages/execnet/gateway_bootstrap.py", line 48, in bootstrap_exec s = io.read(1) File "/lib/python3.6/site-packages/execnet/gateway_base.py", line 402, in read raise EOFError("expected %d bytes, got %d" % (numbytes, len(buf))) EOFError: expected 1 bytes, got 0

and workaround helps me as well

ceph orch host add host2 ip_address
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I faced the same issue as Oleg using cephadm on debian 10.

The workaround was to add the IP address.

sudo ./cephadm shell ceph orch host add host2 ip_address Added host 'host2'
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You may just run without 'cephadm shell', i.e.: $ sudo ceph orch host add host2 ip_address

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