A Linux machine will auto check the file system if the last shutdown was unclean (the system was powered off before the file system was unmounted) or if it has passed to much time since the last check.

This can be turned off in a few ways, here are some.

[never check] From /etc/fstab

If the sixth option is not 0 (or missing) then fsck will do automatic checking, so change the sixth option to a 0.
As root edit the /etc/fstab (use your favorite text editor or vi).

/dev/sda1		/home/files			ext3	defaults	0 0

[never check] By passing arguments via GRUB

It is possible to pass the option fastboot to the kernel at boot time, this will also prevent fsck from running at boot time.
Edit /boot/grub/menu.lst (use your favorite text editor or vi) [might also be called /etc/grub.conf]
So an example of this would look like

title           Debian GNU/Linux, kernel 2.6.26-1-686
root            (hd0,0)
kernel          /vmlinuz-2.6.26-1-686 root=/dev/mapper/root-root--volume ro fastboot
initrd          /initrd.img-2.6.26-1-686

[only skip once] By passing options to shutdown

If you only wish to bypass the automatic testing of the file system once, but keep the automatic settings saved you can use the shutdown command with the option “f”.
For instance to reboot without checking

shutdown -rf now