This chapter contains a brief overview of the build process and instructions for using the three most commonly used image types. The most versatile image type, iso-hybrid, may be used on a virtual machine, optical media or USB portable storage device. In certain special cases, usb-hdd may be more suitable for USB devices. The chapter finishes with instructions for building and using a net type image, which is a bit more involved due to the setup required on the server. This is a slightly advanced topic for anyone who is not familiar already with netbooting, but is included here because once the setup is done, it is a very convenient way to test and deploy images for booting on the local network without the hassle of dealing with image media.
A live system usually means an operating system booted on a computer from a removable medium, such as a CD-ROM or USB stick, or from a network, ready to use without any installation on the usual drive(s), with auto-configuration done at run time (see Terms).
With Debian Live, it's a Debian GNU/Linux operating system, built for one of the supported architectures (currently amd64, i386, powerpc and sparc). It is made from the following parts:
You can use live-build to build the system image from your specifications, set up a Linux kernel, its initrd, and a bootloader to run them, all in one media-dependant format (ISO9660 image, disk image, etc.).
The following sequence of live-build commands will create a basic ISO hybrid image containing just the Debian standard system without X.org. It is suitable for burning to CD or DVD media, and also to copy onto a USB stick (as per Copying USB/HDD image to a USB stick, specifying ".iso" extension where ".img" is indicated).
First, we run the lb config command which will create a "config/" hierarchy in the current directory for use by other commands:
$ lb config
By passing no parameters to lb config, we indicated that we wish to use the defaults (see The lb config command).
Now that we have a "config/" hierarchy, we may build the image with the lb build command:
# lb build
This process can take a while, depending on the speed of your network connection (see The lb build command).
Testing an ISO is simple:
# apt-get install qemu
$ qemu -cdrom binary.iso
In order to test the ISO with virtualbox-ose:
# apt-get install virtualbox-ose virtualbox-ose-dkms
$ virtualbox
Create a new virtual machine, change the storage settings to use binary.iso as the CD/DVD device, and start the machine.
Note: For live systems containing X.org that you want to test with virtualbox-ose, you may wish to include the VirtualBox X.org driver package, virtualbox-ose-guest-x11, in your live-build configuration. Otherwise, the resolution is limited to 800x600.
$ lb config --packages virtualbox-ose-guest-x11
Burning an ISO image is easy:
# apt-get install wodim
$ wodim binary.iso
The following sequence of commands will create a basic USB/HDD image containing just the Debian standard system without X.org. It is suitable for booting from USB sticks, USB hard drives, and various other portable storage devices. Normally, an ISO hybrid image can be used for this purpose instead, but if you have a BIOS which does not handle hybrid images properly, or want to use the remaining space on the media for a persistence partition, you need a USB/HDD image.
Note: if you created an ISO image with the previous example, you will need to clean up your working directory with the lb clean command (see The lb clean command):
# lb clean --binary
Run the lb config command with the parameters to configure the config/ hierarchy to create a USB/HDD image type:
$ lb config -b usb-hdd
Now build the image with the lb build command:
# lb build
The generated binary image contains a VFAT partition and the syslinux bootloader, ready to be directly written on a USB stick. Plug in a USB stick with a size larger than that of binary.img and type:
$ dd if=binary.img of=${USBSTICK}
where ${USBSTICK} is the device file of your key, like /dev/sdb (not a partition like /dev/sdb1!); you can find the right device name by looking in dmesg's output after plugging in the stick, for example, or better yet, ls -l /dev/disk/by-id.
This will definitely overwrite any previous contents on your stick!
Note: As discussed earlier, this same process can be used for iso-hybrid type images (suffixed -hybrid.iso), but not iso type images.
# apt-get install qemu
$ qemu -hda binary.img
If you want to use the remaining free space after you have installed the binary.img, you can use a partitioning tool such as gparted or parted to create a new partition on the stick. The first partition will be used by the Debian Live system.
# gparted ${USBSTICK}
After the creation of the partition, you have to create a filesystem on it. One possible choice would be ext4.
# mkfs.ext4 ${USBSTICK}
If you want to use this data partition with Windows, use FAT32.
# mkfs.vfat -F 32
Remember: Every time you install a new binary.img on the stick, all data on the stick will be lost because the partition table is overwritten by the contents of the image.
The following sequence of commands will create a basic netboot image containing the Debian standard system without X.org. It is suitable for booting over the network.
Note: if you performed any previous examples, you will need to clean up your working directory with the lb clean command:
# lb clean --binary
Run the lb config command as follows to configure your image for netbooting:
$ lb config -b net --net-root-path "/srv/debian-live" --net-root-server "192.168.0.1"
In contrast with the ISO and USB/HDD images, netbooting does not, itself, serve the filesystem image to the client, so the files must be served via NFS. The --net-root-path and --net-root-server options specify the location and server, respectively, of the NFS server where the filesytem image will be located at boot time. Make sure these are set to suitable values for your network and server.
Now build the image with the lb build command:
# lb build
In a network boot, the client runs a small piece of software which usually resides on the EPROM of the Ethernet card. This program sends a DHCP request to get an IP address and information about what to do next. Typically, the next step is getting a higher level bootloader via the TFTP protocol. That could be pxelinux, GRUB, or even boot directly to an operating system like Linux.
For example, if you unpack the generated binary-net.tar.gz archive in the /srv/debian-live directory, you'll find the filesystem image in live/filesystem.squashfs and the kernel, initrd and pxelinux bootloader in tftpboot/debian-live/i386.
We must now configure three services on the server to enable netboot: the DHCP server, the TFTP server and the NFS server.
We must configure our network's DHCP server to be sure to give an IP address to the netbooting client system, and to advertise the location of the PXE bootloader.
Here is an example for inspiration, written for the ISC DHCP server isc-dhcp-server in the /etc/dhcp/dhcpd.conf configuration file:
# /etc/dhcp/dhcpd.conf - configuration file for isc-dhcp-server
ddns-update-style none;
option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;
default-lease-time 600;
max-lease-time 7200;
log-facility local7;
subnet 192.168.0.0 netmask 255.255.255.0 {
range 192.168.0.1 192.168.0.254;
next-server servername;
filename "pxelinux.0";
}
This serves the kernel and initial ramdisk to the system at run time.
You should install the tftpd-hpa package. It can serve all files contained inside a root directory, usually /srv/tftp. To let it serve files inside /srv/debian-live/tftpboot, run as root the following command:
# dpkg-reconfigure -plow tftpd-hpa
and fill in the new tftp server directory when being asked about it.
Once the guest computer has downloaded and booted a Linux kernel and loaded its initrd, it will try to mount the Live filesystem image through a NFS server.
You need to install the nfs-kernel-server package.
Then, make the filesystem image available through NFS by adding a line like the following to /etc/exports:
/srv/debian-live *(ro,async,no_root_squash,no_subtree_check)
and tell the NFS server about this new export with the following command:
# exportfs -rv
Setting up these three services can be a little tricky. You might need some patience to get all of them working together. For more information, see the syslinux wiki at ‹http://syslinux.zytor.com/wiki/index.php/PXELINUX› or the Debian Installer Manual's TFTP Net Booting section at ‹http://d-i.alioth.debian.org/manual/en.i386/ch04s05.html›. They might help, as their processes are very similar.
Netboot image creation is made easy with live-build magic, but testing the images on physical machines can be really time consuming.
To make our life easier, we can use virtualization. There are two solutions.
Edit /etc/qemu-ifup:
#!/bin/sh
sudo -p "Password for $0:" /sbin/ifconfig $1 172.20.0.1
echo "Executing /etc/qemu-ifup"
echo "Bringing up $1 for bridged mode..."
sudo /sbin/ifconfig $1 0.0.0.0 promisc up
echo "Adding $1 to br0..."
sudo /usr/sbin/brctl addif br0 $1
sleep 2
Get, or build a grub-floppy-netboot (in the svn).
Launch qemu with "-net nic,vlan=0 -net tap,vlan=0,ifname=tun0"
#!/usr/bin/vmware
config.version = "8"
virtualHW.version = "4"
memsize = "512"
MemAllowAutoScaleDown = "FALSE"
ide0:0.present = "FALSE"
ide1:0.present = "FALSE"
floppy0.present = "FALSE"
sound.present = "FALSE"
tools.remindInstall = "FALSE"
ethernet0.present = "TRUE"
ethernet0.addressType = "generated"
displayName = "Test Boot PXE"
guestOS = "other"
ethernet0.generatedAddress = "00:0c:29:8d:71:3b"
uuid.location = "56 4d 83 72 5c c4 de 3f-ae 9e 07 91 1d 8d 71 3b"
uuid.bios = "56 4d 83 72 5c c4 de 3f-ae 9e 07 91 1d 8d 71 3b"
ethernet0.generatedAddressOffset = "0"