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Chapter 38. The pcs command-line interface
The pcs
command-line interface controls and configures cluster services such as corosync
, pacemaker
,booth
, and sbd
by providing an easier interface to their configuration files.
Note that you should not edit the cib.xml
configuration file directly. In most cases, Pacemaker will reject a directly modified cib.xml
file.
38.1. pcs help display
You use the -h
option of pcs
to display the parameters of a pcs
command and a description of those parameters.
The following command displays the parameters of the pcs resource
command.
# pcs resource -h
38.2. Viewing the raw cluster configuration
Although you should not edit the cluster configuration file directly, you can view the raw cluster configuration with the pcs cluster cib
command.
You can save the raw cluster configuration to a specified file with the pcs cluster cib filename
command. If you have previously configured a cluster and there is already an active CIB, you use the following command to save the raw xml file.
pcs cluster cib filename
For example, the following command saves the raw xml from the CIB into a file named testfile
.
# pcs cluster cib testfile
38.3. Saving a configuration change to a working file
When configuring a cluster, you can save configuration changes to a specified file without affecting the active CIB. This allows you to specify configuration updates without immediately updating the currently running cluster configuration with each individual update.
For information about saving the CIB to a file, see Viewing the raw cluster configuration. Once you have created that file, you can save configuration changes to that file rather than to the active CIB by using the -f
option of the pcs
command. When you have completed the changes and are ready to update the active CIB file, you can push those file updates with the pcs cluster cib-push
command.
Procedure
The following is the recommended procedure for pushing changes to the CIB file. This procedure creates a copy of the original saved CIB file and makes changes to that copy. When pushing those changes to the active CIB, this procedure specifies the diff-against
option of the pcs cluster cib-push
command so that only the changes between the original file and the updated file are pushed to the CIB. This allows users to make changes in parallel that do not overwrite each other, and it reduces the load on Pacemaker which does not need to parse the entire configuration file.
Save the active CIB to a file. This example saves the CIB to a file named
original.xml
.# pcs cluster cib original.xml
Copy the saved file to the working file you will be using for the configuration updates.
# cp original.xml updated.xml
Update your configuration as needed. The following command creates a resource in the file
updated.xml
but does not add that resource to the currently running cluster configuration.# pcs -f updated.xml resource create VirtualIP ocf:heartbeat:IPaddr2 ip=192.168.0.120 op monitor interval=30s
Push the updated file to the active CIB, specifying that you are pushing only the changes you have made to the original file.
# pcs cluster cib-push updated.xml diff-against=original.xml
Alternately, you can push the entire current content of a CIB file with the following command.
pcs cluster cib-push filename
When pushing the entire CIB file, Pacemaker checks the version and does not allow you to push a CIB file which is older than the one already in a cluster. If you need to update the entire CIB file with a version that is older than the one currently in the cluster, you can use the --config
option of the pcs cluster cib-push
command.
pcs cluster cib-push --config filename
38.4. Displaying cluster status
There are a variety of commands you can use to display the status of a cluster and its components.
You can display the status of the cluster and the cluster resources with the following command.
# pcs status
You can display the status of a particular cluster component with the commands parameter of the pcs status
command, specifying resources
, cluster
, nodes
, or pcsd
.
pcs status commands
For example, the following command displays the status of the cluster resources.
# pcs status resources
The following command displays the status of the cluster, but not the cluster resources.
# pcs cluster status
38.5. Displaying the full cluster configuration
Use the following command to display the full current cluster configuration.
# pcs config
38.6. Modifying the corosync.conf file with the pcs command
As of Red Hat Enterprise Linux 8.4, you can use the pcs
command to modify the parameters in the corosync.conf
file.
The following command modifies the parameters in the corosync.conf
file.
pcs cluster config update [transport pass:quotes[transport options]] [compression pass:quotes[compression options]] [crypto pass:quotes[crypto options]] [totem pass:quotes[totem options]] [--corosync_conf pass:quotes[path]]
The following example command udates the knet_pmtud_interval
transport value and the token
and join
totem values.
# pcs cluster config update transport knet_pmtud_interval=35 totem token=10000 join=100
Additional resources
- For information about adding and removing nodes from an existing cluster, see Managing cluster nodes.
- For information about adding and modifying links in an existing cluster, see Adding and modifying links in an existing cluster.
- For information about modifyng quorum options and managing the quorum device settings in a cluster, see Configuring cluster quorum and Configuring quorum devices.
38.7. Displaying the corosync.conf file with the pcs command
The following command displays the contents of the corosync.conf
cluster configuration file.
# pcs cluster corosync
As of Red Hat Enterprise Linux 8.4, you can print the contents of the corosync.conf
file in a human-readable format with the pcs cluster config
command, as in the following example.
The output for this command includes the UUID for the cluster if the cluster was created in RHEL 8.7 or later or if the UUID was added manually as described in Identifying clusters by UUID.
[root@r8-node-01 ~]# pcs cluster config
Cluster Name: HACluster
Cluster UUID: ad4ae07dcafe4066b01f1cc9391f54f5
Transport: knet
Nodes:
r8-node-01:
Link 0 address: r8-node-01
Link 1 address: 192.168.122.121
nodeid: 1
r8-node-02:
Link 0 address: r8-node-02
Link 1 address: 192.168.122.122
nodeid: 2
Links:
Link 1:
linknumber: 1
ping_interval: 1000
ping_timeout: 2000
pong_count: 5
Compression Options:
level: 9
model: zlib
threshold: 150
Crypto Options:
cipher: aes256
hash: sha256
Totem Options:
downcheck: 2000
join: 50
token: 10000
Quorum Device: net
Options:
sync_timeout: 2000
timeout: 3000
Model Options:
algorithm: lms
host: r8-node-03
Heuristics:
exec_ping: ping -c 1 127.0.0.1
As of RHEL 8.4, you can run the pcs cluster config show
command with the --output-format=cmd
option to display the pcs
configuration commands that can be used to recreate the existing corosync.conf
file, as in the following example.
[root@r8-node-01 ~]# pcs cluster config show --output-format=cmd
pcs cluster setup HACluster \
r8-node-01 addr=r8-node-01 addr=192.168.122.121 \
r8-node-02 addr=r8-node-02 addr=192.168.122.122 \
transport \
knet \
link \
linknumber=1 \
ping_interval=1000 \
ping_timeout=2000 \
pong_count=5 \
compression \
level=9 \
model=zlib \
threshold=150 \
crypto \
cipher=aes256 \
hash=sha256 \
totem \
downcheck=2000 \
join=50 \
token=10000