There are many methods of computer security, such as the power-on password, file encryption, fingerprint recognition, and so on. Today, cows teach you a U disk boot system. Only plug in the U disk system to start, there is no U disk, then you manually guide it ~~~
The principle is very simple, because our ubuntu system is started with grub2, our grub boot program is written on mbr, if we clear the mbr and write boot information on our U disk, then you can only use U Disk boot system slightly. For the master to this method may be some pediatrics, but toss the next fun ~~~
First of all, you have to make sure that your USB drive can be used as a boot device to boot. Don't toss until your USB flash drive can't boot on your computer. Here we can look at their own boot BIOS to support USB devices.
1. Enter our Ubuntu system, where cows use ubuntu 10.10 as an example. Ubuntu 10.04 is 9.10 and 11.0 is the latest. Theoretically, it is okay.
Insert U disk, open the terminal
Fdisk -l looks at which device on the u disk is under /dev/. The cow uses the sdb device as an example.
Then reboot, change the order of boot to usb device over hard disk. See if you can boot into the system normally.
2. Theoretically it should be possible to boot normally, and then we need to make a backup of our ubuntu mbr.
Enter the <a href="http://Www.Guardian.Co.uk/search?q=terminal">terminal</a>
Sudo dd if=/dev/sda of=https://www.nenew.net/mbr.bak bs=446 count=1
Copy mbr.bak in the user directory to your USB flash drive to prevent errors from occurring and the boot is lost.
3. Continue to enter in the terminal
Sudo dd if=/dev/zero of=/dev/sda bs=446 count=1
Fill mbr with 0 to achieve the effect of emptying mbr.
<a href="http://www.Houzz.com/?search=Restart">Restart</a> to see if it can only start with a U disk.
This method suggests that friends who can fully understand can be tossing. Because it is very troublesome to guide Yan, it is not good that the last system can't enter God. If you can't get into the system when you toss it, you can use live-cd to fix the boot. For details, see cow article
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