How to find the name of supergroup in hadoop and list all the members of the group?

[#1]

Hi there,

How to find the name of supergroup in hadoop and list all the members of the group?

I know hdfs is the super user in hadoop, but SuperGroup name

[#2]

Is dfs.permissions.superusergroup in hdfs-site.xml what you are looking for?

[#3]

yes. But, how to list all the users in the superusergroup?

I found superusergroup : hdfs in hdfs-site.xml. But, how to find the users in the group hdfs.

[#4 · Accepted solution]

@Jeeva Jeeva - There is a property "dfs.permissions.superusergroup" in hdfs-site.xml which specifies the superusergroup.

Please see below apache guide for HDFS Permissions:

https://hadoop.apache.org/docs/r2.4.1/hadoop-project-dist/hadoop-hdfs/HdfsPermissionsGuide.html

To list all the users belonging to the supergroup, its just like getting users belonging to a group in linux. Below is good article on that:

https://www.cyberciti.biz/faq/linux-list-all-members-of-a-group/

[#5]

Hi Namit Maheshwari,

Thanks for your time to reply. Your answer saved my life and one more question

How to see the members of the superusergroup for a namenode?

In my case, the super user is "hdfs".

I have been asked to find all the members of the superuser group.

/etc/group file is not for the namenode. So, there should be some other way.

[#6]

Hi Jeeva,

Find the superusergroup value in hdfs-site.xml. Lets say for instance this value is 'hadoop'

Once you find that value, you need to do is "grep 'superusergroup:' /etc/group"

i.e if that value is hadoop, it will be:

grep 'hadoop:' /etc/group

This should return you the list of all users belonging to the supergroup.

[#7]

Hi Maheshwari,

Our superusergroup is hdfs

That's what i did. He asked me where i got these members from and i told from /etc/group file. But, Technical Lead said something different. Here is the conversation we had below.

Jeeva:I got it from /etc/group file

Fred: that is correct for this particular server

how about what namenode?

that's where 'hdfs groups' tell you

[#8]

I think what he means is to check the same on the namenode hosts.

[#9]

Could you suggest me how to check on the namenode?

[#10]

You just need to logon to the namenode hosts and run the same grep command on the /etc/group file

[#11]

Also to find the namenode hosts, just look at the property value for dfs.namenode.rpc-address in hdfs-site.xml

[#12]

Is there any way to find it from ambari without logging to NameNode?

If it is not, how to log on to the namenode from linux(edge node)? sorry for the trivial questiion.

I tried to login from putty, i got exception.

[#13]

I dont think we can get this from Ambari as this is a Linux file, and Ambari is not involved in maintaining that.

As far as logging on to the Namenode, it should be the similar as how you logged on to any other host on the cluster.

We use ssh with a keypair to logon, but thats your environment specific. So, if you have the IP, you should be able to logon to the Namenode host.

[#14]

Anyway.. Thanks for your involvement on this issue. Once i resolved it, I will let you know. I used putty to login but got exception.

[#15]

Ok sure. Yeah I cant say how to logon to your Namenode linux machine. Someone, in your team over there might help.

Also, can you please accept the answer for how to find the supergroup in Hdfs. As, I think you found that information. Thanks!

[#16]

Hi Mahesh,

There is no way to list all members of supergroup. But, we can run for individual user to see if they are belong to the group by using the below command.

hdfs groups <username>

Once again, thanks for time .