[Lustre-discuss] need help debuggin an access permission problem

Tina Friedrich Tina.Friedrich at diamond.ac.uk
Thu Sep 23 07:03:23 PDT 2010


thanks for the answer. I found it in the meantime; one of our ldap 
servers had a wrong size limit entry.

The logs I had of course already looked at - they didn't yield much in 
terms of why, only what (as in, I could see it was permission errors, 
but they do of course not really tell you why you are getting them. 
There weren't any log entries that hinted at 'size limit exceeded' or 

Still - could someone point me to the bit in the documentation that best 
describes how the MDS queries that sort of information (group/passwd 
info, I mean)? Or how to best test that it's mechanisms are working? For 
example, in this case, I always thought one would only hit the size 
limit if doing a bulk 'transfer' of data, not doing a lookup on one user 
- plus I could do these sort lookups fine on all machines involved 
(against all ldap servers).


On 23/09/10 11:20, Ashley Pittman wrote:
> On 23 Sep 2010, at 10:46, Tina Friedrich wrote:
>> Hello List,
>> I'm after debugging hints...
>> I have a couple of users that intermittently get I/O errors when trying
>> to ls a directory (as in, within half an hour, works ->  doesn't work ->
>> works...).
>> Users/groups are kept in ldap; as far as I can see/check, the ldap
>> information is consistend everywhere (i.e. no replication failure or
>> anything).
>> I am trying to figure out what is going on here/where this is going
>> wrong. Can someone give me a hint on how to debug this? Specifically,
>> how does the MDS look up this sort of information, could there be a
>> 'list too long' type of error involved, something like that?
> Could you give an indication as to the number of files in the directory concerned?  What is the full ls command issued (allowing for shell aliases) and in the case where it works is there a large variation in the time it takes when it does work?
> In terms of debugging it I'd say the log files for the client in question and the MDS would be the most likely place to start.
> Ashley,

Tina Friedrich, Computer Systems Administrator, Diamond Light Source Ltd
Diamond House, Harwell Science and Innovation Campus - 01235 77 8442

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