UmVirt Linux From Scratch Virtual Machines

💽	ULFSVM

🔙	Parent Directory	-

About

ULFSVM - UmVirt Linux From Scratch virtual machine disk images and Live CD/DVD/USB disk images.

These images can be installed on real disks and be used as bare metal systems.

Download

Name	Last modified	Size

📁0.1	2024-04-01 03:43	-
📁0.2	2024-04-23 12:38	-
📁0.2.1	2024-09-14 03:29	-
📁0.2.2	2024-02-21 05:07	-
📁4145625122	2024-11-12 03:38	-

Virtual machine disk images

A Linux From Scratch build from sources is too resource expensive. It is requires:

Spending hardware
Spending time
Spending electricity

But, Linux From Scratch from source code can be build from virtual machines. This aproach is more simple and reliable than using real harware.

To reduce costs, we create VMs disk images and share it with the public. If desired, any user can make their own disk images with their own package set.

We use the QEMU hypervisor (emulator) as a back-end for virualization because QEMU is powerful open-source software.

QEMU uses disk images in raw and qcow2 format as VM disk images. It is then possible to convert those disk images from any one format to another other with the qemu-img command-line program.

Raw format

The Raw format is a format where all disk contents stored in a file as-is in bytes sequence.

Pros:

Much better performance than other formats.
Can be transfered to real disks or logical volumes (LVM) with the dd command.
Image does not grow durring usage. If needed, all data will be rewritten.

Cons:

Consumes the entire ammount of storage assigned. The empty space is also reserved.
There is no snapshot support.

QCOW2

The qcow2 format is 'copy on write' format. This format is allows for storing snapshots and modifications separately. In opposition to the raw format, it reserves disk space only when write operations are performed.

Pros:

Lower performance cost than most other formats.
Less disk space needed to get started.
There is snapshot support.

Сons:

Consumes more space if many snapshots are created.
Can't be transfered to real disks or logical volumes (LVM) with dd command. But, the qemu-img program can be used.
Image grows durring usage. If no free disk space available, the virtual machine is paused.

Live CD/DVD/USB disk images

Any UmVirt Linux From Scratch instance can be converted to Live CD/DVD/USB disk images via Linux Live Kit. Images converted with the Live Kit allows for booting UmVirt Linux From Scratch without using HDD/SDD. Also, these images can be used as virtual machine disk images.

A key feature of live CD/DVD/USB disk images is the read only root file system. After every reboot, any modifications are reset. Additional local or remote devices can be used to preserve information.

Disk image flavors

There are many disk images on each release:

lfs - basic Linux From Scratch disk images produced by Umvirt LFSAutoBuilder.
ulfs - advanced lfs disk images produced by Umvirt LFSCustomizer and contain various package sets.
ulfsbe - Umvirt Linux From Scratch Build Environment - Live CD/DVD/USB with Umvirt LFSAutoBuilder and LFSCustomizer.
samples - various sample disk images.

How ULFS disk images are made

Environment

ULFSBE
We use a dedicated server as a virtualization node to run ULFSBE as a virtual machine on the qemu64 platform (we use this platform to avoid any invalid istructions errors).
We use a Local repository to eliminate network influence on the build process.

Build process

LFSAutoBuilder from ULFSBE is used to produce lfs disk images for the i686 and amd64 platforms.
LFSCustomizer is used to upgrade lfs disk images to the initial ulfs disk images.
LFSCustomizer is used to build the console disk images from the initial ulfs disk images by installing additional packages.
LFSCustomizer is used to build the x (XOrg) disk images from the console ulfs disk images by installing additional packages.
LFSCustomizer is used to build the lxde disk images from the x ulfs disk images by installing additional packages.
LFSCustomizer is used to build mate disk images from the lxde ulfs disk images for the qemu64 platform. the mate disk image for the i686 platform is installed manually.

Initial configuration in LFSCustomizer is started with the command:

    ./autoconfig

Additional packages in LFSCustomizer are installed with the commands:

Console
```
./installpackages console
```
Xorg (TWM)
```
./installpackages x
```
Xorg (LXDE)
```
./installpackages lxde
```
Xorg (Mate)
```
./installpackages mate
```

LFSCustomizer tips

To avoid Internet access, turn off dns resolving by running:
```
    systemctl stop systemd-resolved
```
To install packages from local repository, edit ./env.sh

Runing disk images

decompress disk imagse using the gunzip command
attach the disk image to a virtual machine as an IDE/SATA drive
boot the VM
login as root without a password
edit .xinitrc if needed. Then, run:
```
    startlxde
```
or
```
    mate-session
```
run:
```
    startx
```

Creating snapshots

To create the snapshot 'init' on 'x.qcow2' run:
```
    qemu-img snapshot -c init x.qcow2
```
To list the snapshots for 'x.qcow2' run:
```
    qemu-img snapshot -l x.qcow2
```
To load the snapshot 'init' on 'x.qcow2' run:
```
    qemu-img snapshot -a init x.qcow2
```
To delete the snapshot 'init' on 'x.qcow2' run:
```
    qemu-img snapshot -d init x.qcow2
```

Quality Control

In ULFS, no package installation verification is implemented.

To check the package installation logs run the command:

    wc -l /var/log/ulfs-packages/*/files.txt | grep " 0"

This comand will print all the packages where no files were installed.

You can inspect configure.log, build.log, install.log to get more info.

Reduce disk image size

Filling by zeroes

To reduce the disk image size, you can fill unused space with zeroes by using an empty file. Such a file can be created with the command:

    dd if=/dev/zero of=zero.img bs=16384 && rm -v zero.img

    chimp zerofill

After compresson, a Raw disk will consume less disk space. QCOW starts to consume more disk space as write operations are performed. To reduce a QCOW disk image, convert it with the qemu-img command from qcow2 to qcow2.

    qemu-img convert -O qcow2 x.qcow2 new.qcow2

Installation logs removal

You can remove the installation logs directories in /var/log:

lfsautobuilder - LFSAutobuilder logs
lfscustomizer - LFSCustomizer logs
ulfs-packages - ULFS packages logs

Linux kernel sources removal

You can remove the Linux kernel sources directory in /usr/src/linux.

Because the Linux kernel is a particularly important part of the operating system which performs various critical operations like hardware interactions, removing it makes hardware support and reconfiguration more difficult.

Be careful about removing the Linux kernel sources from disk image.