HTTP Error 400: Size of a request header field exceeds server limit

- by admin

I have got an error generated by Apache while configuring Plexcel (PHP Active Directory module):
Error 400: Your browser sent a request that this server could not understand.
Size of a request header field exceeds server limit.

The solution was an easy one: to increase allowed request field size in Apache configuration (/etc/httpd/conf/httpd.conf for RHEL):
LimitRequestFieldSize 16380

Just for information: the default value for LimitRequestFieldSize is equal to 8190.

If you cannot change server settings just try to clean up your browser cookies and limit the size of cookies stored in your browser. It may prevent your browser to send too big request.


Google Chrome Spell Check - crazy message after update

- by admin

I have updated Google Chrome on Red Hat Linux. And to my surprise after restarting Google Chrome I got this:

Google crazy hint







"bettar spell chek" - o la la!

The first idea: maybe there is a problem with my Linux box? But trying Chrome update on Mac and Windows I have got the same results!

I guess they did it on purpose. Just imagine how many Chrome new downloads would be soon!


NetBeans 7.3: Cannot execute Google Chrome

- by admin

I have got today an error in NetBeans 7.3 while starting a HTML5 application in Google Chrome:
Cannot execute /opt/google/chrome/chrome.
Check external browser configuration.

The solution was simple: just change Chrome in Tools / Options / General / Web Browser to

Voilà :-)


How to check DNS cache status in Mac OS X

- by admin

As a follow-up to How to Flush DNS Cache in Mac OS X I have received a question:

how do I know if it worked? In other words, is there a way to check if the DNS cache is cleared?

To see the DNS cache status you may run
sudo killall -INFO mDNSResponder

Thus the SIGINFO signal will dump a snapshot summary of the DNS internal state to

Voilà :-)


.PFX certificate installation on Apache

- by admin

I have got a PFX made with Windows Certificate Services to be installed on Apache. So, using OpenSSL the file (source.pfx) has been converted to Apache compatible format:
openssl pkcs12 -in source.pfx -clcerts -nokeys -out dest.cer

openssl pkcs12 -in source.pfx -nocerts -nodes -out dest.key

The first command extracts public key to dest.cer, the second one extracts private key to dest.key.

The last but not the least is to update Apache configuration file:
SSLEngine on
SSLCertificateFile /path/to/dest.cer
SSLCertificateKeyFile /path/to/dest.key

and to restart Apache :-)

Apache Solr non-ASCII characters

- by admin

This day I had a problem while indexing French and Russian content with Apache Solr: French and Russian characters where corrupted.

The solution was very simple: I added

attribute to the Connector tag which runs Solr in Tomcat's server.xml. Something like
<Connector port="8080" protocol="HTTP/1.1" 
redirectPort="8443" URIEncoding="UTF-8" />

Then Tomcat has to be restarted :-)

Samba start / restart error: smbd_open_once_socket: open_socket_in: Addr

- by admin

Once I have got this problem with samba in Oracle Linux 6 (the same I could reproduce in RedHat 6 as well):

On start or restart of smb service var/log/samba/log.smbd reports:
smbd/server.c:501(smbd_open_one_socket) smbd_open_once_socket: open_socket_in: Address already in use

The solution was:
sysctl net.ipv6.bindv6only=1

as it looks like the problem happens on systems which IPv6 support where :: also listens for IPv4 connections. So the bind to fails.

Your branch is ahead of 'origin/master' by 3 commits or dangling commits

- by admin

Once upon a time, namely today, I run
# git status

and to my big surprise I have got:
# On branch master
# Your branch is ahead of 'origin/master' by 3 commits.
nothing to commit (working directory clean)

Actually I have not done any commits in this local master branch - only pulls from remote. So, next I did
git fsck --no-reflogs

which helped me to get so called ‘dangling commits’ - commits that are under no particular branch:
git fsck --no-reflogs
dangling commit be6b64ba93d9e292b2aeec0a9d3c5209ee83c96f
dangling commit 3229271230d1315924ddd99c5962247d3c3f103b
dangling commit 95c0a7b1611ad0c4c101ff1fa1504d622fa1d2c3

What is exactly in the dangling commit? To get it I run:
git show be6b64ba93d9e292b2aeec0a9d3c5209ee83c96f

Next question: how to delete these dangling commits?

The answer is: wait :-)

Once your reflog entries are expired, those objects will then also be cleaned up by
git gc

Expiry settings are in gc.pruneexpire, gc.reflogexpire and gc.reflogexpireunreachable.

Print-screen (screenshots) in Mac OS X

- by admin

Keyboard shortcuts

  • Command-Shift-3: Take a screenshot of the screen, and save it as a file on the desktop

  • Command-Shift-4, then select an area: Take a screenshot of an area and save it as a file on the desktop

  • Command-Shift-4, then space, then click a window: Take a screenshot of a window and save it as a file on the desktop

  • Command-Control-Shift-3: Take a screenshot of the screen, and save it to the clipboard

  • Command-Control-Shift-4, then select an area: Take a screenshot of an area and save it to the clipboard

  • Command-Control-Shift-4, then space, then click a window: Take a screenshot of a window and save it to the clipboard

In Leopard and later, the following keys can be held down while selecting an area (via Command-Shift-4 or Command-Control-Shift-4):

  • Space, to lock the size of the selected region and instead move it when the mouse moves

  • Shift, to resize only one edge of the selected region

  • Option, to resize the selected region with its center as the anchor point


Different versions of Mac OS X have different formats for screenshots.

  • Mac OS X 10.2 (Jaguar): jpg

  • Mac OS X 10.3 (Panther): pdf

  • Mac OS X 10.4 (Tiger) and later: png

In Mac OS X 10.4 and later, the default screenshot format can be changed, by opening Terminal (located at /Applications/Utilities/Terminal) and typing in:
defaults write type image_format
killall SystemUIServer

Where image_format is one of jpg, tiff, pdf, png, bmp or pict (among others). If you omit the second line, you will need to log out and in again for the change to take effect.

Grab and Preview

Instead of using the keyboard shortcuts above, screenshots can be taken by using the Grab application included with Mac OS X. It is located at /Applications/Utilities/Grab.

In Mac OS X 10.4, the Preview application can also be used to take screenshots, by using the Grab submenu in the File menu.

From the Terminal

The screencapture command in the Terminal can also be used to capture screenshots, and is useful for scripts. Here is an example.
screencapture -iW ~/Desktop/screen.jpg

How to Disable iOS 6 Users Tracking

- by admin

Here is an article I just read, o-la-la - what a scandal...

The most funny thing it how a simple setting is hidden in the menus :-)

Apple Has Quietly Started Tracking iPhone Users Again, And It's Tricky To Opt Out

Apple's launch of the iPhone 5 in September came with a bunch of new commercials to promote the device.

But Apple didn't shout quite so loud about an enhancement to its new mobile operating system, iOS 6, which also occurred in September: The company has started tracking users so that advertisers can target them again, through a new tracking technology called IFA or IDFA.

Previously, Apple had all but disabled tracking of iPhone users by advertisers when it stopped app developers from utilizing Apple mobile device data via UDID, the unique, permanent, non-deletable serial number that previously identified every Apple device.

For the last few months, iPhone users have enjoyed an unusual environment in which advertisers have been largely unable to track and target them in any meaningful way.

In iOS 6, however, tracking is most definitely back on, and it's more effective than ever, multiple mobile advertising executives familiar with IFA tell us. (Note that Apple doesn't mention IFA in its iOS 6 launch page).

Users can switch off that targeting, but it's tricky, as we discovered a couple of days ago. Although at least iOS 6 users are able to turn off tracking, which they weren't before.

Here's how it works.

IFA or IDFA stands for "identifier for advertisers." It's a random, anonymous number that is assigned to a user and their device. It is temporary and can be blocked, like a cookie.

When you look at an app, or browse the web, your presence generates a call for an ad. The publisher's site that you're looking at then passes the IFA to the ad server. The advertiser is then able to know that a specific iPhone user is looking at a specific publication and can serve an ad targeting that user. IFA becomes particularly useful, for instance, if an ad server notices that a particular IFA is looking at a lot of different car sites. Perhaps that user is interested in buying a new car. They'll likely start seeing a lot of car ads on their iPhone.

More importantly, IFA will allow advertisers to track the user all the way to "conversion" — which for most advertisers consists of an app download. Previously, advertisers had no idea whether their ads actually drove people to download apps or buy things. Now IFA will tell them.

The IFA does not identify you personally — it merely provides a bunch of aggregate audience data that advertisers can target with ads.

iOS 6 Settings menu

Tracking is on by default

The new iPhone operating system comes with three things that make tracking easier for advertisers and reduce the likelihood that you'll opt out.

  • iOS 6 comes in a default "tracking on" position. You have to affirmatively switch it off if you do not want advertisers to see what you're up to.

  • The tracking control in iPhone's settings is NOT contained where you might expect it, under the "Privacy" menu. Instead, it's found under "General," then "About," and then the "Advertising" section of the Settings menu.

  • The tracking control is titled "Limit Ad Tracking," and must be turned to ON, not OFF, in order to work. That's slightly confusing — "ON" means ads are off! — so a large number of people will likely get this wrong.

Those three factors combined mean that a huge proportion of iPhone users are unlikely to ever opt out of tracking.

"It's a really pretty elegant, simple solution," says Mobile Theory CEO Scott Swanson. "The biggest thing we're excited about is that it's on by default, so we expect most people will leave it on."

(His take on IFA's capabilities was confirmed by two other mobile ad execs at rival companies.)

Again, IFA doesn't identify you as a person to advertisers. What it does do, however, is provide advertisers with "a really meaningful inference of behavior," Swanson says. "We haven't had access to that information before."

Author: Jim Edwards,

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