How to Promote(Master) and Demote(Worker) a docker swarm node by Raj Gupta

Master:-

To get more details about any node run the inspect command like below for Worker01

[root@ip-172-31-40-90 ~]# docker node inspect u9sg7rw8yvb75o5ybrnppeglo
[
    {
        "ID": "u9sg7rw8yvb75o5ybrnppeglo",
        "Version": {
            "Index": 33
        },
        "CreatedAt": "2019-07-24T09:41:36.258168494Z",
        "UpdatedAt": "2019-07-24T09:41:36.330025943Z",
        "Spec": {
            "Labels": {},
            "Role": "worker",
            "Availability": "active"
        },
        "Description": {
            "Hostname": "ip-172-31-43-91",
            "Platform": {
                "Architecture": "x86_64",
                "OS": "linux"
            },
            "Resources": {
                "NanoCPUs": 1000000000,
                "MemoryBytes": 1033723904
            },
            "Engine": {
                "EngineVersion": "18.06.1-ce",


-----------------------------------------------------------------------------------------

Now to Promote(Master) any node run the below command (promoted both worker node as master)

[root@ip-172-31-40-90 ~]# docker node promote af3y6rhgp328s777kw26g7co2 u9sg7rw8yvb75o5ybrnppeglo
Node af3y6rhgp328s777kw26g7co2 promoted to a manager in the swarm.
Node u9sg7rw8yvb75o5ybrnppeglo promoted to a manager in the swarm.
[root@ip-172-31-40-90 ~]# docker node ls
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
af3y6rhgp328s777kw26g7co2     ip-172-31-35-189    Ready               Active              Reachable           18.06.1-ce
rby7qdb8hc3ebuuy78vpl0i4v *   ip-172-31-40-90     Ready               Active              Leader              18.06.1-ce
u9sg7rw8yvb75o5ybrnppeglo     ip-172-31-43-91     Ready               Active              Reachable           18.06.1-ce
[root@ip-172-31-40-90 ~]#

Now we can run any command(like ls) on any node because both worker node become as master also

-------------------------------------------------------------------------------------------------------

Likewise we can Demote(Worker) any node just change promote command to demote

[root@ip-172-31-40-90 ~]# docker node demote af3y6rhgp328s777kw26g7co2 u9sg7rw8yvb75o5ybrnppeglo

Manager af3y6rhgp328s777kw26g7co2 demoted in the swarm.

Manager u9sg7rw8yvb75o5ybrnppeglo demoted in the swarm.

[root@ip-172-31-40-90 ~]# docker node ls

ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION

af3y6rhgp328s777kw26g7co2     ip-172-31-35-189    Ready               Active                                  18.06.1-ce

rby7qdb8hc3ebuuy78vpl0i4v *   ip-172-31-40-90     Ready               Active              Leader              18.06.1-ce

u9sg7rw8yvb75o5ybrnppeglo     ip-172-31-43-91     Ready               Active                                  18.06.1-ce

[root@ip-172-31-40-90 ~]#

Worker01:-




Worker02:-