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From Alejandro Abdelnur <t...@cloudera.com>
Subject Re: validating user IDs
Date Mon, 11 Jun 2012 23:12:23 GMT

Would be possible using some kind of cmake config magic to set a macro to
the current OS limit? Even if this means detecting the OS version and
assuming its default limit.


On Mon, Jun 11, 2012 at 3:57 PM, Colin McCabe <cmccabe@alumni.cmu.edu>wrote:

> Hi all,
> I recently pulled the latest source, and ran a full build.  The
> command line was this:
> mvn compile -Pnative
> I was confronted with this:
> [INFO] Requested user cmccabe has id 500, which is below the minimum
> allowed 1000
> [INFO] FAIL: test-container-executor
> [INFO] ================================================
> [INFO] 1 of 1 test failed
> [INFO] Please report to mapreduce-dev@hadoop.apache.org
> [INFO] ================================================
> [INFO] make[1]: *** [check-TESTS] Error 1
> [INFO] make[1]: Leaving directory
> `/home/cmccabe/hadoop4/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/target/native/container-executor'
> Needless to say, it didn't do much to improve my mood.  I was even
> less happy when I discovered that -DskipTests has no effect on native
> tests (they always run.)  See HADOOP-8480.
> Unfortunately, it seems like this problem is popping up more and more
> in our native code.  It first appeared in test-task-controller (see
> MAPREDUCE-2376) and then later in test-container-executor
> (HADOOP-8499).  The basic problem seems to be the hardcoded assumption
> that all user IDs below 1000 are system IDs.
> It is true that there are configuration files that can be changed to
> alter the minimum user ID, but unfortunately these configuration files
> are not used by the unit tests.  So anyone developing on a platform
> where the user IDs start at 500 is now a second-class citizen, unable
> to run unit tests.  This includes anyone running Red Hat, MacOS,
> Fedora, etc.
> Personally, I can change my user ID.  It's a time-consuming process,
> because I need to re-uid all files, but I can do it.  This luxury may
> not be available to everyone, though-- developers who don't have root
> on their machines, or are using a pre-assigned user ID to connect to
> NFS come to mind.
> It's true that we could hack around this with environment variables.
> It might even be possible to have Maven set these environment
> variables automatically from the current user ID.  However, the larger
> question I have here is whether this UID validation scheme even makes
> any sense.  I have a user named "nobody" whose user ID is 65534.
> Surely I should not be able to run map-reduce jobs as this user?  Yet,
> under the current system, I can do exactly that.  The root of the
> problem seems to be that there is both a default minimum and a default
> maximum for "automatic" user IDs.  This configuration seems to be
> stored in /etc/login.defs.
> On my system, it has:
> SYSTEM_UID_MIN            100
> SYSTEM_UID_MAX            499
> UID_MIN                  500
> UID_MAX                 60000
> So that means that anything over 60000 (like nobody) is not considered
> a valid user ID for regular users.
> We could potentially read this file (at least on Linux) and get more
> sensible defaults.
> I am also curious if we could simply check whether the user we're
> trying to run the job as has a valid login shell.  System users are
> almost always set to have a login shell of /bin/false or
> /sbin/nologin.
> Thoughts?
> Colin


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