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https://issues.apache.org/jira/browse/HDFS-7146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14161006#comment-14161006
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Allen Wittenauer commented on HDFS-7146:
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bg. See HDFS-4983.
That JIRA is sort of irrelevant to the discussion since HDFS (and therefore
WebHDFS) has no such restrictions on usernames since they are published as
strings. Unix does and we have to play by its rules since that's the space this
code plays.
bq. Seems the requirement on user name varies.
Not really. Some useradd's do not enforce the entire rule set, which is why I
said "most/all". Some Linux distributions include a useradd facility that do
not. If you look at the upstream Linux shadow utilities source, however,
(https://github.com/shadow-maint/shadow/blob/master/libmisc/chkname.c) you'll
find that all digit usernames are not legal. Other OSes follow similar rules
in their utilities ( e.g., Illumos:
https://hg.openindiana.org/upstream/illumos/illumos-gate/file/68f95e015346/usr/src/cmd/aset/tasks/pwchk.awk
). Just because some distributions allowed users to do incredibly dumb things
doesn't mean we need to as well.
FWIW, if you want true portability, you'll need to use the native system calls
to follow whatever rules are allowed on that machine. Otherwise, expect to
make some compatibility decisions. To me, this is an easy call: all numeric
usernames are super rare since they have unpredictable results (e.g., chown).
portability > naive admins who shot themselves in the foot.
> 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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