Debian is an operating system composed of free software mostly carrying the GNU General Public License. The operating system is developed by an internet collaboration of volunteers aligned with The Debian Project.
From debian site
As most of you know, Linux is just a kernel. And, for a long time, the Linux kernel ran only on the Intel x86 series of machines, from the 386 up.
However, this is no longer true, by any means. The Linux kernel has now been ported to a large, and growing, list of architectures. Following close behind, we have ported the Debian distribution to these architectures. In general, this is a process with a sticky start (as we get libc and the dynamic linker working smoothly), and then a relatively routine, if lengthy job, of attempting to recompile all our packages under the new architectures.
Debian is an operating system (OS), not a kernel (actually, it is more than an OS since it includes thousands of application programs)
How exactly this covers our beloved SGS3 (and countless number of other android arm-based phones)?
As you may (or even should!) know, Android operates on it's own Linux-based kernel. Android's kernel is literally a fork of Linux kernel, with a few special/unique functions which are required, mostly hardware-specific. Because of that kernel itself is VERY compatible with everything based on Linux.
However there have always existed one typical problem, lack of proper environment. We have a great kernel, great power, linux-based android environment, but this environment lacks of very common and required libraries/binaries. If you ever wondered what is or what does busybox, this is the answer. Busybox is just a small package which offers a few standalone GNU/Linux binaries, which are required to make certain things work. For example, swap priorities. Android knows what swap is, and nothing else. It doesn't know that swap could have a priority, so if you use android's swapon command on 4 devices, it will firstly fill first device, and then proceed to the next. That's why we need busybox in ALL custom kernels, because android environment isn't enough.
However busybox sometimes isn't enough. If we focus only on Android itself, it is. But if you for example want to run stricly linux-based service, I don't know, a web server for example... Is it possible to run a native linux web server on an android? No, it's not. You should firstly compile such service on arm architecture, including all dynamic and static libraries (wrrr
) in it only to finally get mad because of missing libraries or other dependencies. Of course if you're patient you'd finally compile everything and set up, however how long would it take? A few days maybe? If you're skilled in what you're doing...
This is why I included built-in "pocket" debian in ArchiDroid. It's FULLY
compatible with everything compiled/based on armhf/armel GNU/Linux architecture, for example Raspberry Pi. With two easy commands you can literally jump into debian environment and use every typical GNU/Linux utilities known from debian itself. Of course this means nothing for most of the users, because they'll never have any reason to use such debian environment but from the developer side, it's big step forward. The best example is with github. As you know ArchiDroid has it's own repo on github, from where you can download/manage stuff. There also exists git app for linux and windows. If you want to follow "expert" way of flashing experimental ArchiDroid version, such program is required. The scenario is the same as compiling web server for an android, it requires much more effort than it's worth. And even then you can end up with syncing external dependencies and searching for solutions for the problems you've never seen before... And with ArchiDroid's pocket debian? It's as simple as in any debian/ubuntu distro. "apt-get update && apt-get install git" and voila. Your git is installed and ready for work. Going further I've even included git in pocket debian itself. Okay, I have debian, I have git, and what next? With git utility I can for example provide you with delta updates
for ArchiDroid! ArchiDroid can easily use pocket debian to set up and sync ArchiDroid's repository and then pack and flash latest version without even needing of a PC, using 7-zip or anything else. Another example? A web server. I know that it's very dev-specific but if you for any reason need a web server running, just for example to test simple website, you can have it with just one command. Going further, VNC? MySQL server? PHP? Python? Perl? Ruby? Maybe conditional tasks with cron? Persistent minimal IRC client? rtorrent with rutorrent GUI over WWW? The list goes on... Anything based on linux will work. You can even host a server for your favourite game, as long as it has armhf/armel binaries (unfortunately most of the games don't).
So that's it. In short, debian is an operating system
built-in in ArchiDroid to provide you with (unfortunately missing) GNU/Linux environment, with full power, ready to handle anything you could request. I made my best to include fully working debian in ArchiDroid for a minimal cost. Whole OS is packed in one big tar file, compressed using highest bzip2. As for now pocket debian has ONLY
40 megabytes of size, maybe in future it will have up to 50 megabytes, but no more. It's a VERY small cost for having such great power, especially if you know how to use it.
This is a really cutting-edge feature, mostly because I have no limitiations what I can include in my ROM right now, and while other developers are dealing with OpenDelta updates and many Android-based problems, I'm just launching my pocket debian and manages linux stuff.
I'm SURE that most of the advanced ArchiDroid user will just LOVE this feature, as much as I love it. I'm looking forward to your responses how YOU use pocket debian with your ArchiDroid. It's also a great time to learn what does the debian offer and how you can simplify your common tasks with just one example debian utility
1. Pocket Debian does not cause any additional overhead
. We don't need to use emulation, neither virtualization to boot our monster. I used chroot technology to "jump" into debian environment with already running kernel and Android. That means additional required CPU/RAM is based on what you run in pocket debian. Booting itself doesn't require anything, just about one megabyte of ram for /bin/bash shell
2. Android has some restrictions, mostly sockets. It doesn't allow to create inet sockets by default, even for root users. You will need to add your custom debian users to special group called "inet" (GID 3003) to allow creating of inet sockets, and you may also need to add a group to net_raw group (GID 3004) to allow creating of raw sockets. Please keep in mind that it's only required if you're running an app which required it's own socket, for example mysql server. So apt-get install mysql-server will fail right after booting, you will need to use "addgroup mysql inet" and then apt-get -f install to complete installation. Of course "mysql" is the new user under which mysql-server really operates. I've added root to both of these groups by default.
3. The only "real" restriction is the kernel. Our debian uses Android kernel and it's filesystem. It should work with most common tasks but in some cases our kernel may lack specific modules or built-in code, for example tun/tap required for OpenVPN. Still it's enough to run pretty much everything and if you get in touch with your favourite kernel developer you can also kindly ask for specific missing things.
4. Debian is built and included thanks to debootstrap utility, ArchiDroid command used for creating debian environment is debootstrap --verbose --arch armhf --include=git,ca-certificates,ssh,htop,tightvncserver,xterm,xfonts-base --exclude=manpages,man-db,rsyslog,vim-common,vim-tiny testing debian http://ftp.fr.debian.org/debian
Pocket Debian contains two main terminal commands, "adlinux" and "debian". Both of them are described below. By adlinux and debian you boot and jump into debian's chroot, which means you can use any debian-specific commands.
- changes password of actual user. This is needed to login as specific user, for example through ssh.
service ssh start
- starts local SSH (secure shell) daemon on native port :22, to which you can easily access via any client supporting ssh, f.e. PuTTY. So basicly after you start shell you can literally connect to your local area network (LAN) IP on port 22 f.e. through PuTTY from your PC.
- prints network-related informations about online interfaces, including your local IP, which may be useful for connecting to SSH.
- Enhanced top utility. Gives you very good terminal-based view on actual running processes, used ram, load, and more.
- Syncs with debian's apt repository. This is mandatory to use many of apt commands because ArchiDroid's debian comes without local repo available, however fully configured to download and access it with just one command
apt-get install XXX
- installs packet XXX from debian's repository.
apt-cache search XXX
- searches for all packets including keyword "XXX". Ultra useful in terms of searching for specific packet.
Please note that pocket debian is VERY similar to normal native Debian/Ubuntu distribution, therefore above commands are not ArchiDroid's magic, they're very widely used in Debian/Ubuntu distros. If you want to learn more, most of the Debian/Ubuntu tutorials will be very helpful.