Ubuntu Live USB

Julio Batista Silva

Last updated on Jul 12, 2011 4 min read Linux, Tutorial

I bought a Vantec NexStar CX case to use a 2.5" HDD as an external drive.

Since the HDD has plenty of space and I always need a Linux Live CD to fix something, I decided to install Ubuntu at the beginning of this HDD.

This process is quite simple in Ubuntu, which has a “Disk Creator”, but here in Arch Linux I would need to download a similar program to “Disk Creator” or do it manually. Here I show how to do it manually.

Download the .iso image available at http://www.ubuntu.com/download

Install syslinux and ms-sys

julio@julio-acer ~> sudo pacman -S syslinux mtools
julio@julio-acer ~> yaourt ms-sys

Connect the external HDD to a USB port and check the device using fdisk -l (/dev/sdc here)

julio@julio-acer ~  $  sudo fdisk -l
  Disk /dev/sdc: 500.1 GB, 500107862016 bytes
  171 heads, 40 sectors/track, 142803 cylinders, total 976773168 sectors
  Units = sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  Disk identifier: 0x000de160

     Device Boot      Start         End      Blocks   Id  System
  /dev/sdc1            2048     2099199     1048576    b  W95 FAT32

Make sure the HDD does not contain anything important. Format it, create a partition of at least 1 GB, and mark it as bootable.

julio@julio-acer ~> sudo fdisk /dev/sdc
Command (m for help): d
Selected partition 1

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4, default 1): 1
First sector (2048-976773167, default 2048): 2048
Last sector, +sectors or +size{K,M,G} (2048-976773167, default 976773167): +1G

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): c
Changed system type of partition 1 to c (W95 FAT32 (LBA))

Command (m for help): a
Partition number (1-4): 1

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: If you have created or modified any DOS 6.x
partitions, please see the fdisk manual page for additional
information.
Syncing disks.

Use mkfs to create a FAT32 filesystem:

julio@julio-acer ~  $  sudo mkfs.vfat -F 32 /dev/sdc1

Rewrite the MBR

julio@julio-acer ~  $  sudo dd if=/dev/zero of=/dev/sdc bs=446 count=1
1+0 records in
1+0 records out
446 bytes (446 B) copied, 0.00234799 s, 190 kB/s

julio@julio-acer ~  $  sudo ms-sys -s /dev/sdc
Public domain syslinux master boot record successfully written to /dev/sdc

Mount the external HDD

julio@julio-acer ~  $  sudo mount /dev/sdc1 /media/pendrive/

Install GRUB on the first partition

julio@julio-acer ~  $  sudo grub-install - -no-floppy - -root-directory=/media/pendrive/ /dev/sdc

Mount the .iso image

julio@julio-acer ~  $  sudo mount -o loop ubuntu-11.04-desktop-i386.iso /media/iso/
mount: warning: /media/iso/ seems to be mounted read-only.

Copy the kernel and the initrd from the .iso to the /boot folder

julio@julio-acer ~> sudo cp /media/iso/casper/{vmlinuz,initrd.lz} /media/pendrive/boot/

Reserve a 512MB space for the casper-rw file, which will store all files and modifications made in the system.

julio@julio-acer ~>  sudo dd if=/dev/zero of=/media/pendrive/casper-rw bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 1.92945 s, 278 MB/s

julio@julio-acer ~>  sudo mkfs.ext3 -F /media/pendrive/casper-rw
mke2fs 1.41.14 (22-Dec-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
32768 inodes, 131072 blocks
6553 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=134217728
4 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304

Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 38 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

Create a second partition to store the .iso

julio@julio-acer ~> sudo fdisk /dev/sdc
    Command (m for help): n
    Command action
       e   extended
       p   primary partition (1-4)
    p
    Partition number (1-4, default 2): 2
    First sector (2099200-976773167, default 2099200):
    Using default value 2099200
    Last sector, +sectors or +size{K,M,G} (2099200-976773167, default 976773167): +730M

    Command (m for help): w
    The partition table has been altered!

    Calling ioctl() to re-read partition table.
    Syncing disks.

Copy the files from the .iso to the second partition

julio@julio-acer ~> sudo dd if=ubuntu-11.04-desktop-i386.iso of=/dev/sdc2
1403484+0 records in
1403484+0 records out
718583808 bytes (719 MB) copied, 116.572 s, 6.2 MB/s

Edit the Grub menu

julio@julio-acer .../pendrive/boot/grub> cat menu.lst
default         0
timeout         10

title           Ubuntu (Live)
root            (hd0,0)
kernel          /boot/vmlinuz boot=casper file=/preseed/ubuntu.seed persistent
initrd          /boot/initrd.lz

Unmount the disk, set the BIOS to boot from USB, and test your live USB.

Ubuntu Live USB

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Julio Batista Silva

Data Engineer