antiX LiveCD/USB Tips and Techniques for creating LiveUSBs

LiveCD/USB Guide
Tips and Techniques for creating LiveUSBs

## Creating antiX LiveUSBs

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tl;dr:

- Label the boot partition and use bootlabel

- Align your partitions and use large block sizes

- Use a boot directory containing the antiX version in its name

- Leave space for remastering and/or root and home persistence

### Advantages

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A LiveUSB has many advantages over a LiveCD:

- It boots much faster

- It is smaller and more rugged

- It usually has a much larger capacity

- You can write to it so you can have persistence and remastering

- You can have multiple partitions, including swap

- You can have several different versions on the same USB stick

### Disadvantages

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But there are some disadvantages as well:

- A LiveCD is read-only so it can be more secure than a LiveUSB

- Many older computers can’t boot from a USB stick but they can boot from a CD

## Why re-invent the wheel?

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Many tools already exist to create a LiveUSB from a LiveCD iso image. Why don’t we just use the existing tools and be done with it? The answer is because the existing tools don’t let you take advantage of the new features that a LiveUSB makes possible, in particular: persistence, remastering and multiple operating systems. In addition, it is now possible to make LiveUSBs that boot more reliably.

### Game Plan

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The basic idea is to do a frugal install on a single large partition with the three basic files (vmlinuz, initrd.gz, and linuxfs) in a single directory that is labeled by the antiX version and kernel type (486 or 686). In addition, we label this partition so the bootstrap program doesn’t have to go searching for it. I like to use an ext2 or ext3 filesystem although it is possible to use a fat32 (or other) filesystem.

- Do a "Frugal Install" by copying the linuxfs file

- Put all three boot files in the same directory labeled by OS and version

- Add a label to the boot partition

### Example

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In this example we will put three different versions of antiX (12 686 full, 12 686 base, and 12 486 core) on the same USB stick. follow the convention that "686" and "full" are defaults and thus can be omitted from the directory names. Here is the file layout on the boot partition:

    /antiX-12
        vmlinuz
        initrd.gz
        linuxfs

    /antiX-12-base
        vmlinuz
        initrd.gz
        linuxfs

    /antiX-12-core-486
        vmlinuz
        initrd.gz
        linuxfs

    /boot/grub/
        menu.lst
        etc ...

    /boot/isolinux
        isolinux.cfg
        etc ...

Here are the three (partial) Grub entries:

    title antiX-12 Full 686
    kernel /antiX-12/vmlinuz blab=antiXlive bdir=antiX-12
    initrd /antiX-12/initrd.gz

    title antiX-12 Base 686
    kernel /antiX-12-base/vmlinuz blab=antiXlive bdir=antiX-12
    initrd /antiX-12-base/initrd.gz

    title antiX-12 Core 486
    kernel /antiX-12-core-486/vmlinuz blab=antiXlive bdir=antiX-12
    initrd /antiX-12-core-486/initrd.gz

I’ve used abbreviated versions of bootdir (bdir) and bootlabel (blab). You will generally need and want other boot parameters.

## Adding Goodies

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### MD5 Checksums

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We will perform an optional md5sum check on files in the directory containing the linuxfs file and files in the directory containing the ISO file (if the fromiso option is used). For every file you want checked, make a second fle with the `.md5` extension tacked on to the end of the file name containing the md5 checksum. For example:

    # md5sum linuxfs > linuxfs.md5

Typically, this will only be used for the linuxfs file and/or the ISO file but we’ll check every file that has a md5 checksum file. Since this check will delay the boot process, we only perform the check of the check boot parameter was given. You can create a Grub menu entry that enables this option if you want.

### Remastering

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The only thing the LiveUSB creator has to do to enable live-remastering is to make sure there is enough room on the boot partition for another linuxfs file. The standard antiX-12 linuxfs files range in size from 110 Meg to 670 Meg. The size of a new linuxfs file will depend on the size of the original linuxfs file and also on how much has been added or subtracted.

If the file system on the boot partition handles symlinks then you may want to name the linuxfs file either `linuxfs.00` or `linuxfs.orig` and create a symlink to it called `linuxfs`:

    # ln -s linuxfs.00 linuxfs

This will make it easier to keep track of which linuxfs file is which in the case when there is repeated remastering and the user wants to keep the previous versions either as backups or as snapshots.

### Persistent root and home

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## Gory Details

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### Partitioning

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alignment

    # mkfs.ext4 -q -m 0 -O ^has_journal -L LiveUSB -N 400 /dev/sdb1

### Copying Files

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???

### Installing Grub

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Install on both mbr and on boot partition

    # grub
    find /boot/memtest
    root (hd2,0)
    setup (hd2)
    setup (hd2,0)
    quit