Monthly Archives: October 2010

How to change the timeout in GRUB2?

Sometimes booting your Linux system can be relatively long. It depends often on how many services your system needs to start while booting.

There’s also a phase which takes time: the boot-loader. It displays a menu in which you can choose which kernel to use or starting another operating system. If you don’t choose anything, there is a timeout and then the boot-loader picks up the default kernel/operating system.

Ubuntu 10.10 sets this timeout to 10 seconds which can be seen as long. It’s possible to change that.

How? Well the boot-loader used by Ubuntu is GRUB2. Since 9.10 (Karmic Koala) and the file for configuring it is /etc/default/grub.

In Ubuntu you need to use sudo for editing this file (replace emacs by your editor of choice):
sudo emacs /etc/default/grub

Then you need to find the setting GRUB_TIMEOUT and change its value to 3 seconds for instance:

Save the file and you have done most of the work!

To achieve it, you need now to run update-grub to update the file /boot/grub/grub.cfg:
~$ sudo update-grub
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-2.6.35-22-generic
Found initrd image: /boot/initrd.img-2.6.35-22-generic
Found linux image: /boot/vmlinuz-2.6.32-25-generic
Found initrd image: /boot/initrd.img-2.6.32-25-generic
Found memtest86+ image: /boot/memtest86+.bin
Found Windows 7 (loader) on /dev/sda1

You can now reboot your system if you want to test it 🙂

PHP: isset () vs strlen ()

How to test the length of a string in PHP ?  Well, PHP has a function called strlen () for this purpose.
So obviously, a simple if (strlen ($str) > 10) { ... } should do the trick, isn’t it?

Actually, there’s another way to do that: considering that a string is an array of characters, it’s possible to test if a character is set at the length we want to check with isset (). So the line of code above should be replace by if (isset ($str [10]) { ... }.

Why should we use isset () instead of strlen ()?

Well, it’s way faster: running the test above 100 000 times for each function gives me:
strlen () : 0.034812927246094 seconds
isset () : 0.0079290866851807 seconds