How do you fine duplicates? What if I want to know where the duplicates are?

The trick is to use count() and compare it to an integer.

SELECT count(*), locations.* FROM locations GROUP BY number HAVING COUNT(*) > 1

That will select a count of unique instances of a value from a table called “locations”, group them by a field called “number” where the count is greater than 1. In other words, it will return all the fields where there are more than one instance of the same value in the column “number”.

Using mysqladmin if there is no password:

$ mysqladmin -u root password <new password>

Using mysqladmin if there is a password:
$ mysqladmin -u root -p <old password> <new password>

Using mysql shell if there is no password
mysql -u root
mysql> update user set password=PASSWORD("<new password>") where User='root';
mysql> flush privileges;
mysql> quit

Using mysql shell if there is a password
mysql -u root -p
Password: <old password>
mysql> update user set password=PASSWORD("<new password>") where User='root';
mysql> flush privileges;
mysql> quit

Recover/reset the password if you don’t know it
There is no way to recover the password if you don’t know it, but you can reset it to something new.
You must have root on the box for this.

1. Kill the running server
2. Create a text file with the following contents:
   UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
FLUSH PRIVILEGES;
3. Run the mysql_safe binary with the --init-file option pointing to your new file like this:
   mysqld_safe --init-file=/path/to/file &
4. Delete the init file you created.
5. Stop and start MySQL normally.

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To update the group policy, run Gpupdate.exe from a cmd window.  This is refresh any changes in the Group Policy as they apply to that machine.  Run Gpupdate.exe /Force from a cmd window in order to force a full refresh of the Group Policy.

You have to check Event Log -> Application to see if it actually succeeded.

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If you qmail-smtpd under tcpserver, the following will update relay allow and relay forbid rules.

Create a file called /etc/tcp.smtp and put in it:

127.:allow,RELAYCLIENT=""
1.1.1.1:allow,RELAYCLIENT=""
2.2.:allow,RELAYCLIENT=""
2.2.2.5:deny

Qmail uses simple pattern matching so only classful subnets are allowed. Sorry, no CIDR notation.

The example above will allow/deny:

• Allow relaying from 127.* your localhost subnet of 127.0.0.0/8
• Allow the /32 address of 1.1.1.1
• Allow 2.2.* the /16 subnet of 2.2.0.0/16
• Specifically forbid 2.2.2.5

In order to implement these rules you need to update the server tcp.smpt.cbd file and restart Qmail.

First, back up /etc/tcp.smtp, then run the command:
tcprules /etc/tcp.smtp.cdb /etc/tcp.smtp.tmp < /etc/tcp.smtp

If the rules don’t update, make sure -x /etc/tcp.smtp.cdb is after tcpserver in your start script, then restart Qmail.

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Will give you:

$VAR1 = {
'key2' => 'value2',
'key1' => 'value1'
};
$VAR2 = {
'key2' => 'value2',
'key1' => 'value1'
};
$VAR3 = {
'key2' => 'value2',
'key1' => 'value1'
};


Snazzy!

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This post was updated on 8/29/2008 to clarify a few things

This is a heavily viewed page. Please leave me a comment if this was helpful or if something is missing or confusing.  I would like it to be more comprehensive.

Shouts to Lavrik for getting this started.

To calculate heat output (BTU) of your systems, you need to remember (or read below) your high school electrical class. There are three questions to answer.

1. How much power am I going to draw?
2. How much heat will that power useage generate?
3. How much cooling do I need for that heat?

How much power am I going to draw?

Power is measured in Watts and used in math as the letter ‘P’. The formula for calculating power requires Volts (How much juice you can provide) and Amperes (How hard you suck on the straw).

Power in Watts (P) = Volts (V) * Current in Amperes (I) or:

P = V * I

If you know how many Watts your power supplies can feed and you know how much voltage you have, you can figure out your Amperes.

Take a simple server:

- A server with a 1000 Watt power supply.
- 208 Volt service.
- Running at theoretical maximum load.

P = 1000
V = 208
I = ?

I = P/V or 1000/208 = 4.8 Amperes

So now that you know how much you’re tugging on the grid, find out how much heat that will produce.

How much heat will that power usage generate?

BTUs or British Thermal Units are heat measurements. Generally measured in per-hour increments. In common usage 12,000 BTU/h is considered a Ton. This is important because we cool and heat over time so we need to know how much cooling to throw in to the room per hour.

1 Watt will produce 3.412 BTU per hour

To calculate the BTU/heat output of a system, substitute BTUs for Watts and use the following equation:

BTU/h = (V * I) * 3.412

Using the example server above running full blast in a sealed room with no air moving in and out and no heat loss through the walls you can do the math:

BTU/h = 3.412 x 1000 = 3412BTU/h

How much cooling do I need for that heat?

About 1/3 Ton of cooling is required to cool this system. However, your actual requirements will probably be lower because we can assume you won’t run the equipment at full capacity and there is some energy loss through the walls, ceiling and floors.

Using the techniques above, you can make a simple worksheet to calculate your total theoretical maximum cooling requirements. Don’t forget to take in to account other sources of heat. Ambient building temperature (do you have hot walls from the boiler in the next room?), lights, cooling compressor (it should list it’s heat output) and other equipment.

You can probably undercut your requirements if your equipment does not run at full capacity, but be sure you leave enough room to grow and to keep up in case a cooling unit fails or you experience a period of heavy load and you do use your gear at capacity.

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Warning: Unknown: Releasing SysV semaphore id 58 key 0×152b in request cleanup in Unknown on line 0


This is not an error from WordPress, but from the WP Super Cache Plugin you forgot you installed. The error comes when from the cache directory is not writable.

Change the permissions on the wp-content/cache directory to allow the web user to write and the error will disappear.

The solution is obvious if you check the source code on the page when the error appears. WP Super Cache spits out the error, but it is hidden in HTML comment tags. Your source code will look something like this:

<!-- Dynamic Page Served (once) in 0.297 seconds -->
<!-- File not cached! Super Cache Couldn't write to: wp-content/cache/wp-cache-2876abde8ce3a2aa817c8289ea85486e.html -->

87
<br />
<b>Warning</b>: Unknown: Releasing SysV semaphore id 58 key 0x152b in request cleanup in <b>Unknown</b> on line <b>0</b><br />

The fastest way to deny based on RBL is to add it to whatever ACL you specify in acl_smtp_rcpt

However, you MUST put the declaration AFTER any relay allow definitions. ACLs are based on first-match which means they run in order and stop when they hit a match. Implicit allow.

Here is my ACL declared as acl_check_rcpt

acl_check_rcpt:
  accept  hosts = :
  deny    local_parts   = ^.*[@%!/|] : ^\\.
  accept  local_parts   = postmaster
          domains       = +local_domains
  require verify        = sender
  accept  domains       = +local_domains
          endpass
          message       = unknown user
          verify        = recipient
  accept  domains       = +relay_to_domains
          endpass
          message       = unrouteable address
          verify        = recipient
  accept  hosts         = +relay_from_hosts
  accept  authenticated = *
  deny    dnslists = zen.spamhaus.org
          message = Message rejected because $sender_fullhost is blacklisted at $dnslist_domain see $dnslist_text
  deny    message       = relay not permitted

The RBL definition is toward the bottom, after we allow everyone in that we want in. This lets people relay via SMTP-AUTH or explicit allow before checking the RBL. If they aren’t allowed via anything we allow, then we check the RBL and die with a nice message.

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The problem lies in escaping characters in your SQL queries. Do I addslashes()? Is magic_quotes_gpc enabled?

My quick-and-dirty solution is the following function:


function request_cleanup()
{
  if(get_magic_quotes_gpc() == 0)
  {
    foreach($_REQUEST as $req_key => $req_value)
    {
      $_REQUEST[$req_key]=addslashes($_REQUEST[$req_key]);
    }
  }
}


By calling that function on every page that deals with inserting content in to the database, I know will will get my content escaped correctly.

Of course it escapes all submitted content, including that which isn’t going in to the database so don’t forget to stripslashes() when you are working with data that doesn’t need it.

Example:

request_cleanup();

print “Your note was: $confirmation”;