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https://issues.apache.org/jira/browse/HDFS-7146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14160678#comment-14160678
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Yongjun Zhang commented on HDFS-7146:
-------------------------------------
Hi [~aw],
Thanks for the info you provided. Here is what the comment says (man getent):
{code}
group When no key is provided, use setgrent(3), getgrent(3), and
endgrent(3) to enumerate the group database. When one or more key arguments
are provided, pass each
numeric key to getgrgid(3) and each nonnumeric key to
getgrnam(3) and display the result.
passwd When no key is provided, use setpwent(3), getpwent(3), and
endpwent(3) to enumerate the passwd database. When one or more key arguments
are provided, pass each
numeric key to getpwuid(3) and each nonnumeric key to
getpwnam(3) and display the result.
{code}
If user name 123 has uid 456, and we do "getent passwd 123", it will think 123
is uid, and search for user with uid 123, which may not exist, this is when we
get back nothing.
About "id" command, I tested it on centos and mac (thanks for
[[email protected]]'s help), would you please comment whether it's good enough
and what could be missed? The nfs code is said to support linux and mac only.
Thanks.
> NFS ID/Group lookup requires SSSD enumeration on the server
> -----------------------------------------------------------
>
> Key: HDFS-7146
> URL: https://issues.apache.org/jira/browse/HDFS-7146
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: nfs
> Affects Versions: 2.6.0
> Reporter: Yongjun Zhang
> Assignee: Yongjun Zhang
> Attachments: HDFS-7146.001.patch, HDFS-7146.002.allIncremental.patch,
> HDFS-7146.003.patch
>
>
> The current implementation of the NFS UID and GID lookup works by running
> 'getent passwd' with an assumption that it will return the entire list of
> users available on the OS, local and remote (AD/etc.).
> This behaviour of the command is advised to be and is prevented by
> administrators in most secure setups to avoid excessive load to the ADs
> involved, as the # of users to be listed may be too large, and the repeated
> requests of ALL users not present in the cache would be too much for the AD
> infrastructure to bear.
> The NFS server should likely do lookups based on a specific UID request, via
> 'getent passwd <UID>', if the UID does not match a cached value. This reduces
> load on the LDAP backed infrastructure.
> Thanks [~qwertymaniac] for reporting the issue.
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