question Re: How to find the name of supergroup in hadoop and list all the members of the group? in Archives of Support Questions (Read Only)

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

JeevaKrish — Thu, 23 Mar 2017 22:56:58 GMT

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

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

deepesh1 — Thu, 23 Mar 2017 23:10:17 GMT

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

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

namaheshwari — Thu, 23 Mar 2017 23:18:54 GMT

@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/

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

JeevaKrish — Fri, 24 Mar 2017 00:01:11 GMT

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.

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

namaheshwari — Fri, 24 Mar 2017 00:15:30 GMT

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.

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

JeevaKrish — Fri, 24 Mar 2017 00:23:38 GMT

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

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

namaheshwari — Fri, 24 Mar 2017 00:27:14 GMT

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

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

JeevaKrish — Fri, 24 Mar 2017 00:37:49 GMT

Could you suggest me how to check on the namenode?

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

JeevaKrish — Fri, 24 Mar 2017 00:41:01 GMT

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.

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

namaheshwari — Fri, 24 Mar 2017 00:58:44 GMT

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

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

namaheshwari — Fri, 24 Mar 2017 01:01:40 GMT

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

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

JeevaKrish — Fri, 24 Mar 2017 01:14:35 GMT

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.

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

namaheshwari — Fri, 24 Mar 2017 01:25:01 GMT

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.

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

JeevaKrish — Fri, 24 Mar 2017 01:43:50 GMT

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.

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

namaheshwari — Fri, 24 Mar 2017 01:53:27 GMT

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!

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

JeevaKrish — Fri, 24 Mar 2017 02:31:22 GMT

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 .