Server Restarting Every 2 Hours

Hi there,

First of all, let me say that I'm a web developer and have very limited knowledge on server management but am a fast learner, so I've done a lot of research on what needs to be done to fix this issue, but I can't for the life of me figure it out.

So I started noticing that every 2 hours or so, the server "reboots" itself for a few minutes to the point where even linode graphs are showing the gap. There is an actual gap and not that the statistics have dropped to zero. Here's the screenshot - notice the two hour gaps between 5am onwards:

~~http://i.imgur.com/TOfnwKL.png" />

Before this, as you can see in the IO rate, I thought that, that was the cause of the issue. Disk thrashing - but even after fixing that issue (I was accidentally saving cache to disk instead of APC), the restarts were still persistent.

Now thinking this was a memory issue, I had our server migrated to Dallas so that we could upgrade to 1GB from 512MB. Now let me add here that this is a server that is only running a single wordpress site. It's nothing too fancy, but seems to be taking up a lot for some reason.

I setup the server using https://github.com/okor/LEMPress - LEMPress as suggested by one of the users on the Linode IRC channel.

Now I'm thinking that the server is running out of memory, but I don't see any errors that would suggest so.

Here is my my.cnf config - http://p.linode.com/7571

I've run mysqltuner and go the following results:

-------- General Statistics --------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.5.29-0ubuntu0.12.04.2
[OK] Operating on 64-bit architecture

-------- Storage Engine Statistics -------------------------------------------
[--] Status: -Archive -BDB -Federated +InnoDB -ISAM -NDBCluster
[--] Data in MyISAM tables: 357K (Tables: 18)
[--] Data in InnoDB tables: 18M (Tables: 25)
[--] Data in PERFORMANCE_SCHEMA tables: 0B (Tables: 17)
[!!] Total fragmented tables: 26

-------- Performance Metrics -------------------------------------------------
[--] Up for: 29m 48s (1K q [0.582 qps], 106 conn, TX: 3M, RX: 106K)
[--] Reads / Writes: 100% / 0%
[--] Total buffers: 192.0M global + 2.7M per thread (40 max threads)
[OK] Maximum possible memory usage: 299.5M (30% of installed RAM)
[OK] Slow queries: 0% (0/1K)
[OK] Highest usage of available connections: 5% (2/40)
[OK] Key buffer size / total MyISAM indexes: 16.0M/217.0K
[OK] Query cache efficiency: 28.6% (247 cached / 863 selects)
[OK] Query cache prunes per day: 0
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 105 sorts)
[!!] Temporary tables created on disk: 30% (136 on disk / 449 total)
[OK] Thread cache hit rate: 98% (2 created / 106 connections)
[OK] Table cache hit rate: 24% (85 open / 344 opened)
[OK] Open file limit used: 8% (84/1K)
[OK] Table locks acquired immediately: 100% (756 immediate / 756 locks)
[OK] InnoDB data size / buffer pool: 18.5M/128.0M

-------- Recommendations -----------------------------------------------------
General recommendations:
    Run OPTIMIZE TABLE to defragment tables for better performance
    MySQL started within last 24 hours - recommendations may be inaccurate
    Enable the slow query log to troubleshoot bad queries
    When making adjustments, make tmp_table_size/max_heap_table_size equal
    Reduce your SELECT DISTINCT queries without LIMIT clauses
Variables to adjust:
    tmp_table_size (> 16M)
    max_heap_table_size (> 16M)

It just seems a bit weird that it happens every two hours consistently. I've run the script crontab -l and it said there were no cronjobs for the root user - so I'm at a loss. I was hoping that someone would be able to point me in the right direction?

Thank you in advance for any help you can provide.~~