Troubleshooting

You might need to investigate why a cephadm command failed or why a certain service no longer runs properly.

Cephadm deploys daemons as containers. This means that troubleshooting those containerized daemons might work differently than you expect (and that is certainly true if you expect this troubleshooting to work the way that troubleshooting does when the daemons involved aren’t containerized).

Here are some tools and commands to help you troubleshoot your Ceph environment.

Pausing or disabling cephadm

If something goes wrong and cephadm is behaving badly, you can pause most of the Ceph cluster’s background activity by running the following command:

ceph orch pause

This stops all changes in the Ceph cluster, but cephadm will still periodically check hosts to refresh its inventory of daemons and devices. You can disable cephadm completely by running the following commands:

ceph orch set backend ''
ceph mgr module disable cephadm

These commands disable all of the ceph orch ... CLI commands. All previously deployed daemon containers continue to exist and will start as they did before you ran these commands.

See Disabling automatic deployment of daemons for information on disabling individual services.

Per-service and per-daemon events

In order to help with the process of debugging failed daemon deployments, cephadm stores events per service and per daemon. These events often contain information relevant to troubleshooting your Ceph cluster.

Listing service events

To see the events associated with a certain service, run a command of the and following form:

ceph orch ls --service_name=<service-name> --format yaml

This will return something in the following form:

service_type: alertmanager
service_name: alertmanager
placement:
  hosts:
  - unknown_host
status:
  ...
  running: 1
  size: 1
events:
- 2021-02-01T08:58:02.741162 service:alertmanager [INFO] "service was created"
- '2021-02-01T12:09:25.264584 service:alertmanager [ERROR] "Failed to apply: Cannot
  place <AlertManagerSpec for service_name=alertmanager> on unknown_host: Unknown hosts"'

Listing daemon events

To see the events associated with a certain daemon, run a command of the and following form:

ceph orch ps --service-name <service-name> --daemon-id <daemon-id> --format yaml

This will return something in the following form:

daemon_type: mds
daemon_id: cephfs.hostname.ppdhsz
hostname: hostname
status_desc: running
...
events:
- 2021-02-01T08:59:43.845866 daemon:mds.cephfs.hostname.ppdhsz [INFO] "Reconfigured
  mds.cephfs.hostname.ppdhsz on host 'hostname'"

Checking cephadm logs

To learn how to monitor the cephadm logs as they are generated, read Watching cephadm log messages.

If your Ceph cluster has been configured to log events to files, there will exist a cephadm log file called ceph.cephadm.log on all monitor hosts (see Ceph daemon logs for a more complete explanation of this).

Gathering log files

Use journalctl to gather the log files of all daemons:

Note

By default cephadm now stores logs in journald. This means that you will no longer find daemon logs in /var/log/ceph/.

To read the log file of one specific daemon, run:

cephadm logs --name <name-of-daemon>

Note: this only works when run on the same host where the daemon is running. To get logs of a daemon running on a different host, give the --fsid option:

cephadm logs --fsid <fsid> --name <name-of-daemon>

where the <fsid> corresponds to the cluster ID printed by ceph status.

To fetch all log files of all daemons on a given host, run:

for name in $(cephadm ls | jq -r '.[].name') ; do
  cephadm logs --fsid <fsid> --name "$name" > $name;
done

Collecting systemd status

To print the state of a systemd unit, run:

systemctl status "ceph-$(cephadm shell ceph fsid)@<service name>.service";

To fetch all state of all daemons of a given host, run:

fsid="$(cephadm shell ceph fsid)"
for name in $(cephadm ls | jq -r '.[].name') ; do
  systemctl status "ceph-$fsid@$name.service" > $name;
done

List all downloaded container images

To list all container images that are downloaded on a host:

Note

Image might also be called ImageID

podman ps -a --format json | jq '.[].Image'
"docker.io/library/centos:8"
"registry.opensuse.org/opensuse/leap:15.2"

Manually running containers

Cephadm writes small wrappers that run a containers. Refer to /var/lib/ceph/<cluster-fsid>/<service-name>/unit.run for the container execution command.

ssh errors

Error message:

execnet.gateway_bootstrap.HostNotFound: -F /tmp/cephadm-conf-73z09u6g -i /tmp/cephadm-identity-ky7ahp_5 root@10.10.1.2
...
raise OrchestratorError(msg) from e
orchestrator._interface.OrchestratorError: Failed to connect to 10.10.1.2 (10.10.1.2).
Please make sure that the host is reachable and accepts connections using the cephadm SSH key
...

Things users can do:

  1. Ensure cephadm has an SSH identity key:

    [root@mon1~]# cephadm shell -- ceph config-key get mgr/cephadm/ssh_identity_key > ~/cephadm_private_key
    INFO:cephadm:Inferring fsid f8edc08a-7f17-11ea-8707-000c2915dd98
    INFO:cephadm:Using recent ceph image docker.io/ceph/ceph:v15 obtained 'mgr/cephadm/ssh_identity_key'
    [root@mon1 ~] # chmod 0600 ~/cephadm_private_key
    

If this fails, cephadm doesn’t have a key. Fix this by running the following command:

[root@mon1 ~]# cephadm shell -- ceph cephadm generate-ssh-key

or:

[root@mon1 ~]# cat ~/cephadm_private_key | cephadm shell -- ceph cephadm set-ssk-key -i -
  1. Ensure that the ssh config is correct:

    [root@mon1 ~]# cephadm shell -- ceph cephadm get-ssh-config > config
    
  2. Verify that we can connect to the host:

    [root@mon1 ~]# ssh -F config -i ~/cephadm_private_key root@mon1
    

Verifying that the Public Key is Listed in the authorized_keys file

To verify that the public key is in the authorized_keys file, run the following commands:

[root@mon1 ~]# cephadm shell -- ceph cephadm get-pub-key > ~/ceph.pub
[root@mon1 ~]# grep "`cat ~/ceph.pub`"  /root/.ssh/authorized_keys

Failed to infer CIDR network error

If you see this error:

ERROR: Failed to infer CIDR network for mon ip ***; pass --skip-mon-network to configure it later

Or this error:

Must set public_network config option or specify a CIDR network, ceph addrvec, or plain IP

This means that you must run a command of this form:

ceph config set mon public_network <mon_network>

For more detail on operations of this kind, see Deploying additional monitors

Accessing the admin socket

Each Ceph daemon provides an admin socket that bypasses the MONs (See Using the Admin Socket).

To access the admin socket, first enter the daemon container on the host:

[root@mon1 ~]# cephadm enter --name <daemon-name>
[ceph: root@mon1 /]# ceph --admin-daemon /var/run/ceph/ceph-<daemon-name>.asok config show

Restoring the MON quorum

In case the Ceph MONs cannot form a quorum, cephadm is not able to manage the cluster, until the quorum is restored.

In order to restore the MON quorum, remove unhealthy MONs form the monmap by following these steps:

  1. Stop all MONs. For each MON host:

    ssh {mon-host}
    cephadm unit --name mon.`hostname` stop
    
  2. Identify a surviving monitor and log in to that host:

    ssh {mon-host}
    cephadm enter --name mon.`hostname`
    
  3. Follow the steps in Removing Monitors from an Unhealthy Cluster

Manually deploying a MGR daemon

cephadm requires a MGR daemon in order to manage the cluster. In case the cluster the last MGR of a cluster was removed, follow these steps in order to deploy a MGR mgr.hostname.smfvfd on a random host of your cluster manually.

Disable the cephadm scheduler, in order to prevent cephadm from removing the new MGR. See Enable Ceph CLI:

ceph config-key set mgr/cephadm/pause true

Then get or create the auth entry for the new MGR:

ceph auth get-or-create mgr.hostname.smfvfd mon "profile mgr" osd "allow *" mds "allow *"

Get the ceph.conf:

ceph config generate-minimal-conf

Get the container image:

ceph config get "mgr.hostname.smfvfd" container_image

Create a file config-json.json which contains the information neccessary to deploy the daemon:

{
  "config": "# minimal ceph.conf for 8255263a-a97e-4934-822c-00bfe029b28f\n[global]\n\tfsid = 8255263a-a97e-4934-822c-00bfe029b28f\n\tmon_host = [v2:192.168.0.1:40483/0,v1:192.168.0.1:40484/0]\n",
  "keyring": "[mgr.hostname.smfvfd]\n\tkey = V2VyIGRhcyBsaWVzdCBpc3QgZG9vZi4=\n"
}

Deploy the daemon:

cephadm --image <container-image> deploy --fsid <fsid> --name mgr.hostname.smfvfd --config-json config-json.json