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Apache rewrite rule: conditionally strip HTTP header

With mod_headers, you can set, unset, and modify HTTP headers in Apache.

To conditionally set / unset a header, you have to do a bit of a roundabout process and make use of environment variables. In other words, you have to do a test for the condition and set an environment variable based on the result. Then, you can use a RequestHeader directive based on the environment variable.

In this specific example, I wanted to strip an X-Forwarded-Host header only for a specific subdomain. This is because the subdomain was being used to proof the site through a proxy, but I didn’t want the content management system (CMS) behind it to generate links based on the subdomain; I wanted the CMS to generate links based on the normal site domain / URL.

RewriteRule ^.*$ - [ENV=ISPROOFSITE:true]
RequestHeader unset X-Forwarded-Host env=ISPROOFSITE

You can do something similar with the mod_setenvif Apache module together with the mod_headers module.

SetEnvIf X-Forwarded-Host proof\.yoursite\.com ISPROOFREQUEST
RequestHeader unset X-Forwarded-Host env=ISPROOFSITE

Bonus notes: here’s an example of how to block traffic based on an X-Forwarded-For header. This is useful if you are behind a reverse proxy such as Akamai or Varnish and you cannot block the source IP directly (since the source IP is of the reverse proxy); in these cases, usually you have an X-Forwarded-For or True-Client-IP HTTP header that represents the end client’s IP address.

RewriteCond %{HTTP:X-Forwarded-For}i 123\.127\.77\.38 [OR]
RewriteCond %{HTTP:X-Forwarded-For}i 124\.127\.45\.59 [OR]
RewriteCond %{HTTP:X-Forwarded-For}i 87\.164\.134\.73
RewriteRule ^(.*) - [F]

Transferring a dual-boot hard drive to an SSD (Samsung Evo 840)

When I upgraded my standard “spinning disk” hard drive to an SSD, I didn’t want to have to re-install the operating systems and all of the applications. The particular SSD I bought (Samsung Evo 840) came with a specific application aptly called “Samsung Data Migration” for transferring all of the data. It has very straightforward steps, enabling you to size the partitions on the new drive based on the existing partitions on the old drive and of course copy the data. In my case, I had a dual-boot setup with Windows 7 and Ubuntu but Samsung Data Migration did not recognize the Ubuntu partition. It only recognized the Windows 7 partitions.

I had previously used a program called DriveImage XML to migrate data from an old to a new hard drive with good success. However, it had the same problem in that it did not show the Ubuntu partition.

I ended up successfully using another program called Clonezilla. It is a free and open source program that runs a bit differently than Samsung Data Migration or DriveImage XML. With Clonezilla, you have to burn it onto a bootable CD/DVD or make a bootable USB drive. Then, you reboot your computer and the Clonezilla distribution / operating system will do a live boot on the CD/DVD or USB drive. (There is another option: you can also put Clonezilla on the new hard drive so that you don’t need a separate disk or USB device.) Clonezilla recognized all of my hard drive partitions and successfully copied both the Windows 7 and Ubuntu operating systems to my new hard drive (which I’d plugged in to the computer via a USB hard drive enclosure). Once the copy is complete, you can turn off your computer, physically install the new drive in place of the old drive, and you’re done!

Clonezilla is much more powerful than the Samsung Data Migration program but definitely less user-friendly. However, Clonezilla is very well documented on its website, and not just for the setup process. For example, there is step-by-step documentation for the disk-to-disk clone, complete with screenshots.

CanadianForex review: great foreign exchange rates and support

I’ve been using XE Trade for a few years for personal currency exchange and international funds transfers for my small business. I started to try CanadianForex a few months ago and have been very pleased with its rates and support.

The basic premise is relatively straightforward and the same as XE Trade: you submit currency exchange deals through their online interface, send them the money in the source currency, and they deliver the money in the destination currency to your account or a foreign account within a few days. Therefore, you can use it for currency exchanges between your own accounts, or to send money internationally (as long as it’s between different currencies). Especially for sending money internationally on a regular basis, using an online service is often much more convenient than a traditional bank.

Here’s my review of CanadianForex, specifically compared against XE Trade.


Creating an account at CanadianForex is very straightforward, although just like XE Trade, you have to provide (for a business account, at least) some sensitive information to them, including:

  • A signed bank statement
  • A client agreement form signed by 2 directors
  • A copy of your driver’s licence

Exchange rates

I’ve found CanadianForex’s exchange rates to be better than XE Trade, at least for transferring between Canadian dollars and: US dollars, Euros, and Australian dollars. CanadianForex’s standard fee is $15 for transactions under $10,000 (and no fees for transactions above $10,000); while XE Trade usually charges no fees at all, CanadianForex is still better (as of January 2015) by a significant amount for trades that are more than a few hundred dollars.

Some example comparisons between CanadianForex and XE Trade after deducting the CanadianForex fee:

  • Sending approximately $5,500 CAD to Australia (AUD): the recipient got 40 AUD more with CanadianForex
  • Sending approximately $8,000 CAD to Germany (EUR): the recipient got 48 EUR more with CanadianForex
  • Sending approximately $7,000 CAD to the United States (USD): the recipient got 50 USD more with CanadianForex

In the case of sending money to Brazil, CanadianForex still charges the same $15 fee, whereas XE Trade charges an additional $22 wire fee. This resulted in similar savings as above with CanadianForex.

I’ve also found CanadianForex’s exchange rates to be slightly better than RBC’s foreign exchange rates, at least for transferring US dollars to Canadian dollars within my business account. However, the difference was only a few dollars for some of sample amounts I tested.


The trades happen completely online, although you have to speak to a CanadianForex representative over the phone to complete your initial account setup, and you also receive a verification phone call from them after your first trade.

To book a trade, you must first set up recipients, including their bank account information. Then, you get a quote for the exchange you’d like to make, and click a “Finalise” button. If you’ve set up direct debit, the money will be removed from your account by the next business day. Otherwise, you send CanadianForex the money using your bank’s bill payment system. Once CanadianForex receives the money, they will send an Electronic Funds Transfer (EFT) or wire payment, depending on the destination country, to the recipient.

Customer service

You can contact CanadianForex by phone or e-mail. This is the same as with XE Trade. However, CanadianForex really emphasizes personal contact by assigning you a specific account manager (for a business account at least) and making you speak to them so that they can walk you through their services over the phone. With XE Trade you can set up your account and trade for years without ever needing talking to a person, let alone be assigned a specific contact.

I once had an issue when XE Trade mysteriously removed one of my recipient records without notifying me, and refused to tell me why when I phoned them. After I pushed for some explanation over the phone, they promised to follow up and never did. The recipient was eventually re-instated, although I was never notified about this. Of course, there is a chance that this could happen with CanadianForex, but I expect that they would be more communicative and cooperative with me in such a case. And to be fair, the situation with XE Trade might have been an edge case.

Other notes

  • Weekends and holidays: CanadianForex is closed on weekends and holidays. In other words, you can sign in to your account but you cannot submit any trades. This is probably a good thing; with XE Trade I discovered that the exchange rate spread was much worse on weekends and holidays versus normal business days.

Sony VAIO Y Series RAM: use 2Rx8 instead of 1Rx8

I recently upgraded a Sony VAIO Y Series laptop’s RAM from 4GB (2 sticks of 2GB) to 8GB (2 sticks of 4GB). (For those who have the VPCY216FD model, 8GB is the maximum supported amount of RAM.)

There are a few main things to look out for when upgrading RAM:

  • Size: laptop RAM is typically 200-pin and labelled “SODIMM” whereas desktop RAM is typically 240-pin
  • Speed part 1: DDR2 vs DDR3 for example
  • Speed part 2: PC3-8500 for example

All 3 of the above are usually clearly stated in retail listings and classifieds such as Craigslist or eBay. The first 2 elements are usually obvious and the third is usually OK if you get a speed equal or higher than what your computer supports.

There is another factor called memory rank that has to do with the physical density of the RAM. In my case, the possible ranks were 2Rx8 (roughly allowing 8 memory “nodes” on each side of the RAM stick) and 1Rx8 (again with 8 memory “nodes” but only on one side of the RAM stick).


For most newer laptops, the difference in memory rank does not matter. For the particular Sony VAIO Y Series model I had, the memory that I bought for the upgrade did not work — the laptop would not start booting Windows and would automatically reboot after a few seconds.

The online listing for the RAM I purchased never mentioned the memory rank; as it turns out, the RAM I had received was 1Rx8 and I found no available documentation stating that the laptop would not support 1Rx8. (In fact, the pictured clearly showed 2Rx8 on the sticker, but I received something different.) After much Googling, I found a forum post where someone else mentioned that their Sony laptop only worked with the 2Rx8 memory rank. I returned the 1Rx8 RAM and made sure to buy 2Rx8 RAM. Sure enough, the 2Rx8 RAM worked!

CTRL+Shift keyboard language change in Windows 7

For quite a while I couldn’t figure out why my keyboard would suddenly switch to French mode. The question mark would turn into a capital, accented É; the “#” symbol would turn into a forward slash; and more. I had to close the program I was in and re-open it to restore the standard US keyboard layout. As it turns out, pressing CTRL+Shift on the keyboard is a common shortcut for changing the keyboard language on Windows 7. If you find yourself with your keyboard language layout suddenly changed, just press CTRL+Shift until the correct layout returns.

You can check your keyboard language settings by clicking “Region and Language” in the control panel…

Control panel region and language settings

… then click on the “Keyboards and Languages” tab and click the “Change keyboards…” button:

Keyboards and languages

You can then see the configured keyboard layouts and the “hot key” for changing languages:

Advanced Key Settings

I was accidentally triggering the layout change by using the CTRL+Shift+V shortcut to paste text and remove the formatting (bold, italics, headers, and so on) in the source text.

Copy and paste but remove formatting

CTRL+V is the standard shortcut to paste text, but most programs will try to preserve the formatting, which you don’t always want; and when you want to preserve the formatting, sometimes the destination program messes it up! In programs that support it, CTRL+Shift+V strips the formatting so that you don’t first have to paste into another program such as Notepad and then copy and paste into the destination program. Just be careful about accidentally changing your keyboard language if you press CTRL+Shift instead of CTRL+Shift+V!