Troubleshooting¶

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

Cephadm deploys daemons within containers. This means that troubleshooting those containerized daemons will require a different process than traditional package-install daemons.

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 facilitate debugging failed daemons, 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 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 be a ceph.cephadm.log file on all monitor hosts (see Ceph daemon logs for a more complete explanation).

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 uses small wrappers when running 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 Ceph administrators can do:

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 -

Ensure that the SSH config is correct:

[root@mon1 ~]# cephadm shell -- ceph cephadm get-ssh-config > config

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

Running Various Ceph Tools¶

To run Ceph tools like ceph-objectstore-tool or ceph-monstore-tool, invoke the cephadm CLI with cephadm shell --name <daemon-name>. For example:

root@myhostname # cephadm unit --name mon.myhostname stop
root@myhostname # cephadm shell --name mon.myhostname
[ceph: root@myhostname /]# ceph-monstore-tool /var/lib/ceph/mon/ceph-myhostname get monmap > monmap
[ceph: root@myhostname /]# monmaptool --print monmap
monmaptool: monmap file monmap
epoch 1
fsid 28596f44-3b56-11ec-9034-482ae35a5fbb
last_changed 2021-11-01T20:57:19.755111+0000
created 2021-11-01T20:57:19.755111+0000
min_mon_release 17 (quincy)
election_strategy: 1
0: [v2:127.0.0.1:3300/0,v1:127.0.0.1:6789/0] mon.myhostname

The cephadm shell sets up the environment in a way that is suitable for extended daemon maintenance and running daemons interactively.

Restoring the Monitor Quorum¶

If the Ceph monitor daemons (mons) cannot form a quorum, cephadm will not be able to manage the cluster until quorum is restored.

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

Stop all mons. For each mon host:

ssh {mon-host}
cephadm unit --name mon.`hostname` stop

Identify a surviving monitor and log in to that host:
```
ssh {mon-host}
cephadm enter --name mon.`hostname`
```
Follow the steps in Removing Monitors from an Unhealthy Cluster

Manually Deploying a Manager Daemon¶

At least one manager (mgr) daemon is required by cephadm in order to manage the cluster. If the last mgr in a cluster has been removed, follow these steps in order to deploy a manager called (for example) mgr.hostname.smfvfd on a random host of your cluster manually.

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

ceph config-key set mgr/cephadm/pause true

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

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

Analyzing Core Dumps¶

When a Ceph daemon crashes, cephadm supports analyzing core dumps. To enable core dumps, run

ulimit -c unlimited

Core dumps will now be written to /var/lib/systemd/coredump.

Note

Core dumps are not namespaced by the kernel, which means they will be written to /var/lib/systemd/coredump on the container host.

Now, wait for the crash to happen again. To simulate the crash of a daemon, run e.g. killall -3 ceph-mon.

Install debug packages including ceph-debuginfo by entering the cephadm shelll:

# cephadm shell --mount /var/lib/systemd/coredump
[ceph: root@host1 /]# dnf install ceph-debuginfo gdb zstd
[ceph: root@host1 /]# unzstd /mnt/coredump/core.ceph-*.zst
[ceph: root@host1 /]# gdb /usr/bin/ceph-mon /mnt/coredump/core.ceph-...
(gdb) bt
#0  0x00007fa9117383fc in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007fa910d7f8f0 in std::condition_variable::wait(std::unique_lock<std::mutex>&) () from /lib64/libstdc++.so.6
#2  0x00007fa913d3f48f in AsyncMessenger::wait() () from /usr/lib64/ceph/libceph-common.so.2
#3  0x0000563085ca3d7e in main ()