Make a live USB Key running Ubuntu with large persistent storage for persistent mode

Today we are going to make a live USB key with persistent mode. This is a USB key that contain an operating system that runs just like the one on your computer.

A live USB key is a USB key that can boot from your computer. Not all live USB keys can boot right from the key : some are just used to install an OS on your computer, just like a CD. The mode where you can actually run the OS right from the USB key is called persistent mode.
Usual live USB keys with persistent mode made using Linux distributions usually cannot use more than 4GB of data for persistent mode, whatever the size of your USB key is. This is because of some FAT32 restriction. We are going to bypass these limitations so you can use as much space as you want for your portable live and persistent OS.

Installing the OS

• Download LinuxLive USB Creator (LiLi for short).
• Insert your USB Key and launch LiLi USB Creator. Select your USB key. Then, either choose an ISO you downloaded, or use the download button to let LiLi download the latest release of you selected OS. Here, we are going to use Ubuntu 14.04. Allow for some persistent space (the size does not matter, we are going to modify it later). The setup should look like this:Now you are ready to click the lightning icon to start the installation.
• Go to your USB key. You should have only one folder visibleThe installed files are actually hidden so you do not modify them too much. Go to  View -> Options -> View -> Disable temporarily Hide Protected operating system files. Now you should see the installed files on the key.Go to boot/grub/ and open grub.cfg to modify it. grub.cfg is the file used when the key boot, to show the options you have when running the key. Add the new entry below as the first menuentry:

menuentry "Run persistent mode" {
set gfxpayload=keep
linux      /casper/vmlinuz.efi persistent file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash --initrd     /casper/initrd.lz
}
Save and exit.

Make a secondary partition

Key to allow for more than 4GB persistent storage is to make a secondary partition that will be used to store persistent data. Making multiple partition on USB keys is not common, and most OS do not cope with it. Windows for example will simply ignore secondary partitions. We will thus need EaseUS Partition Manager Software to do so. You can download it freely here.

By default, a file is created on the primary partition for storing all those files. Its name is “casper-rw” and it is located in the root of the key. Delete it.

Let’s create a secondary partition now. Open EaseUS Partition software, select your USB key partition and click Resize-Move partition. Resize to the size you want (free the space on the right, as the second partition must come after the primary one). The primary partition will be used for the basic files of the OS and for usual USB key usage. The space you spare will be used for the persistent files only. It will be invisible to most OS. I personally used a 64GB USB key, kept 30GB for the primary partition and the rest for the persistent mode.

Then, format the free space you just spared. Use EXT3 or EXT4 format, name it casper-rw, and cluster size 4KB. Apply the modifications. The partition must be set to primary partition.

Boot from the USB drive

Now, you should be all set to use your new OS! It is now important to ensure that the computer you will use accept to boot using USB keys. You should look into the bios of your computer to ensure that USB-Storage is one of the possible boot option.

Most recent computers running Windows 8 or newer use secure mode to boot. This mode usually only allow you to boot from Windows, preventing other external system to take control of the computer. This mode can prevent the system from booting into your USB drive, even if you specify USB-Storage as one of your boot options. You will have to disable secure boot in order to boot from the Key. This setting can be found in the boot section of your bios.

If your computer still boots to your usual OS, press F12 repeatedly while the computer boots until you arrive on such screen:

There, select USB Storage Device.

Once this is done, you should be able to boot and have the grub menu showing. Enter the persistent mode.

You should now be able to use your Ubuntu OS and do whatever you want right from your USB key. Enjoy!

If you encounter any problem during the creation of the USB key or the booting, put a comment below to get some help.

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