aurora git commit: Explain observer `--mesos-root` configuration.

[js...@apache.org]

Repository: aurora
Updated Branches:
  refs/heads/master 7d57cf4d7 -> 17ddc484f


Explain observer `--mesos-root` configuration.

This adds a note about configuration of the observer's `--mesos-root` to
match the Mesos master `--work_dir` for proper observer functioning.

Bugs closed: AURORA-1617

Reviewed at https://reviews.apache.org/r/43534/


Project: http://git-wip-us.apache.org/repos/asf/aurora/repo
Commit: http://git-wip-us.apache.org/repos/asf/aurora/commit/17ddc484
Tree: http://git-wip-us.apache.org/repos/asf/aurora/tree/17ddc484
Diff: http://git-wip-us.apache.org/repos/asf/aurora/diff/17ddc484

Branch: refs/heads/master
Commit: 17ddc484f732285d3c8811dde1bbf5dd0fbcf821
Parents: 7d57cf4
Author: John Sirois <js...@apache.org>
Authored: Fri Feb 12 12:42:08 2016 -0700
Committer: John Sirois <js...@apache.org>
Committed: Fri Feb 12 12:42:08 2016 -0700

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 docs/installing.md | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)
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http://git-wip-us.apache.org/repos/asf/aurora/blob/17ddc484/docs/installing.md
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diff --git a/docs/installing.md b/docs/installing.md
index 1620a6f..c4e25c5 100644
--- a/docs/installing.md
+++ b/docs/installing.md
@@ -220,9 +220,33 @@ For more detail on this topic, see the dedicated page on
         sudo yum install -y aurora-executor
 
 ### Configuration
-The executor and observer typically do not require much configuration.  Command line arguments can
+The executor typically does not require configuration.  Command line arguments can
 be passed to the executor using a command line argument on the scheduler.
 
+The observer needs to be configured to look at the correct mesos directory in order to find task
+sandboxes. You should 1st find the Mesos working directory by looking for the Mesos master
+`--work_dir` flag. You should see something like:
+
+        ps -eocmd | grep "mesos-master" | grep -v grep | tr ' ' '\n' | grep "\--work_dir"
+        --work_dir=/var/lib/mesos
+
+The value you find for `--work_dir`, `/var/lib/mesos` in this example, should match the Aurora
+observer value for `--mesos-root`.  You can look for that setting in a similar way on a worker
+node by grepping for `thermos_observer` and `--mesos-root`.  If the flag is not set, you can view
+the default value like so:
+
+        thermos_observer -h
+        Options:
+          ...
+          --mesos-root=MESOS_ROOT
+                                The mesos root directory to search for Thermos
+                                executor sandboxes [default: /var/lib/mesos]
+          ...
+
+In this case the default is `/var/lib/mesos` and we have a match. If there is no match, you can
+either adjust the mesos-master start script(s) and restart the master(s) or else adjust the
+Aurora observer start scripts and restart the observers.
+
 ## Installing the client
 ### Ubuntu Trusty