dalixOS

Packages

Sources

We will be using our own sources format detailed in Developer Info

Pkg Bundle Structure

For an example package of libsqsh

/System/Packages/libsqsh---1.2.3/
├── pkg-info
└── root
	├── usr
	│	└── ...
	└── ... (basically an app installed to a chroot)

Metadata file

# ./pkg-info

# currently only type 1 description files are supported.
InfoType = 1
DepsIncluded = false

# Neccesary fields
[Package]

Name = "Your Package Name"
Version = "4.5.6"
Architecture = "Architecture in the same format as debians e.g. amd64 arm64 etc."
Maintainer = "You/Your company's name"
Description = '''
The first line is the short description.
All the other lines are a description
which can span multiple lines.
'''

Depends = "libsqsh (>= 1.2.3), python (>= 3.10) | python3 (>= 3.10), joy, happiness, love, etc."
# A mix of Enhances, Suggests,
Recommends = "peace"
Suggests = "family"
PreDepends = "life"

# For use in automated scripts so there only has to be one meta-data file
[Other]
source = "deb"
manually_installed = true

When (a) package(s) are/is pulled in by an app.

Their are two methods for starting this container, the symlink method and the overlayfs method. The current implementation is currently working on implementing the overlayfs method due to its’ simplicity and security, but potentially in the future the symlink method may be implemented.

Symlink method

First, all of the packages are added to a list of needed ones, this prevents recursion issues. Then, in an involved process, pkg calulates bwrap arguments. This process goes as follows.

~~- First, We ```overlay``` the base system read-only with a tmpfs overtop so we can bind mount without changing the base system. e.g. ``` ... --overlay-src / --tmp-overlay / ... ```~~

Then we bind mount the System, Users, and Volumes.

	--bind /System /System
	--bind /Users /Users
	--bind /Volumes /Volumes

Then we develop a tree of all the files and folders that need to be symlinked, along with their occurence count. As a bare minimum example.

 usr             = 2
 usr/bin         = 2
 usr/bin/bwrap   = 1
 usr/bin/bash    = 1
 usr/share/bwrap = 1
 usr/share/bash  = 1

Any files or folders that have an occurence count of 1 can be symlinked. For files with an occurence count greater then 1, the file closest to the main package in the dependency tree will be chosen. For folders with an occurence count greater then 1, they will be created in the argument list

Then we symlink those. For example

	--mkdir usr
	--mkdir usr/bin
	--mkdir usr/share
	--symlink /System/Packages/bubblewrap0.11.0/root/usr/bin/bwrap /usr/bin/bwrap
	--symlink /System/Packages/bash5.6.7/root/usr/bin/bash /usr/bin/bash
	--symlink /System/Packages/bubblewrap0.11.0/root/usr/share/bubblewrap /usr/share/bubblewrap
	--symlink /System/Packages/bash5.6.7/root/usr/share/bash /usr/share/bash

Potentially, if the cost of preforming the symlinks for every package/application gets to high, a static solution may have to be implemented. For now it will be done for each package/application.

OverlayFS Method

The overlayfs method involves overlaying all of the packages overtop of one another. It will be a large amount of packages but there are potential optimizations. The general procedure is as follows.

First, we calculate all of the directories that need to be overlayed. For example.

/System/Packages/liba---1.2.3/root
/System/Packages/libqt---4.5.6/root
/System/Packages/qt-tools---4.5.6/root
...

We also need to add the base package to that list
```
/System/Packages/base---0.1.0/root
```
Then we overlay them together with a tmpfs over the top. For example.

--overlay-src /System/Packages/liba---1.2.3/root
--overlay-src /System/Packages/libqt---4.5.6/root
--overlay-src /System/Packages/qt-tools---4.5.6/root
--overlay-src /System/Packages/base---0.1.0/root
--tmp-overlay /

Also, there is a special package in the system called base, it is not the system but rather a special package that is pulled in by all the others, it is nothing more then a pkg-info and (optionaly) a debian rootfs. An application with sufficient priveleges, can add itself/another package to base’s dependencies, to get automatically pulled in. For instance, an application installing a font, would create a package for the font, and add it into base’s deps.

base
├── pkg-info
└── root

The base system is also added to base’s dependencies. More info in MakeISO

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