Android startup & rom/kernel structure questions - Android Q&A, Help & Troubleshooting

I'm after an overview of the startup process and structure of the rom/kernel interaction.
As I understand it we have:
Bootmanager -> loads Kernel, sets up filesystems?
Kernel -> sets up filesystems?, initialises devices/sensors and loads interface(aka rom)
rom then controls main user interface, invoking dalvik and apps etc.
Is this a reasonable accurate view?
Is there a document somewhere giving a little detail on this sort of thing?
Is there a standard naming convention or layout for the file systems in memory prior to their initialisation? Or is it dependent on the kernel?
Im interested in how we go from a layout in memory to a running system and how the system is laid out in the memory before the system starts. How fluid are the boundarys and sizes of the different components and how a developer can replace individual components.
I'm interested in learning a little about embedded systems and it strikes me that playing with a couple of android devices would be a good place to start learning.
thanks

Related

[REF] Information for Beginners

A great guide for newcommers and others alike, all credit goes to the original poster (appdroid)
Originally Posted by appdroid
I don't take any credit I Googled everything. I do take credit of modifying some stuff in word. The idea came from here. I may have took some of his work. SO credit him and Pirateghost for the information about Android.
ADB → Android Debug Bridge (adb) is a versatile command line tool that lets you communicate with an emulator instance or connected Android-powered device..
Android →Unveiled on 5 November 2007, Android is a mobile operating system running on the Linux kernel developed by Google.
ASOP → Android Open Source Project
Apps2SD → Move applications from the internal NAND memory on the device to a removable SD Card.
Bloatware → Software bloat is a process whereby successive versions of apps include an increasing proportion of unnecessary features that are not used by end users, or generally use more system resources than necessary, while offering little or no benefit to its users. Like all the crap that comes from At&t
Brick → When used in reference to consumer electronics, "brick" describes a device that cannot function in any capacity (such as a device with damaged firmware). This usage derives from the fact that some electronic devices (and their detachable power supplies) are vaguely brick-shaped, and so those which do not function are useful only as actual bricks. The term can also be used as a verb. For example, "I bricked my phone when I tried to modify its firmware."
Hard Brick → When your phone does not turn on at all. When you can’t get in to CWR/CWM Or Stock recovery. You are basically screwed.
Soft Brick → When your phone bootloops. When you can get into CWR/CWM. When You can use jigtag to get into download mode.
Busybox → BusyBox provides several stripped-down Unix tools in a single executable. It runs in a variety of POSIX environments such as Linux, Android, FreeBSD and others, such as proprietary kernels, although many of the tools it provides are designed to work with interfaces provided by the Linux kernel. It was specifically created for embedded operating systems with very limited resources. Platforms counterparts, but they are pretty close and useful nonetheless.
CWR OR CWM ClockworkMod Recovery →A custom recovery for Android phones and tablets that allows you to perform several advanced recovery, restoration, installation and maintenance operations on your Android device that aren’t possible with the stock recovery.
DEODEX → Apk files have respective odexes that devs use to supposedly save space. Deodexing means you convert it back to a .dex file and put it back inside the apk. This allows you to easily replace file (not having to worry about odexes), but the main point was to deodex services.jar so that you can change all text to different colors (such as the clock color to white) and to deodex services.jar, you need to deodex everything.
Flashing → The process of applying a firmware image (or ROM) to a device. It generally entails a very specific order of steps. Failing to complete any one of these steps properly may result in bricking the device.
Firmware ​→ is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices. Programs stored in the ROM, EPROM, or flash memory that usually control various internal electronic devices (Hard Drives, Keyboards, Displays, etc). Firmware is typically 'fixed' software that is not updated in consumer devices, however it is often updated (or 'flashed') by advanced users to fix bugs or add features to the device. Flashing firmware designed for one device onto a different device, or not following a specific procedure while flashing will often render the device unusable.
Kernel → is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources (the communication between hardware and software components
Radio → The cellular radio on the device which needs control software called firmware to control it.
ROM → Read Only Memory. In the context of an Android device, ROM is the internal flash memory where the core operating system resides. It can also refer to a specific version firmware that can be applied to a device through a process usually referred to as flashing. An improperly flashed ROM can often brick the device, rendering it unusable.
Superuser→ A program, which gives unlimited access privileges to perform any or all operations on the operating system.
ODIN → Odin is the Samsung software used to update Samsung phones. It does not work with any other devices other than official Samsung phones.
OTA or FOTA → (F)OTA stands for (Firmware) Over The Air and is the process by which required updates and enhancements to your phone's basic operating system can be sent to you through the cellular network. The Galaxy S II software update will be sent via FOTA and is available through Samsung Kies mini.0
ODEX → In Android file system, applications come in packages with the extension .apk. These application packages, or APKs contain certain .odex files whose supposed function is to save space. These ‘odex’ files are actually collections of parts of an application that are optimized before booting. Doing so speeds up the boot process, as it preloads part of an application. On the other hand, it also makes hacking those applications difficult because a part of the coding has already been extracted to another location before execution.
SDK → Software Development Kit.
Logcat → A debugging tool built into Android devices that displays system logs as they occur. See Logcat.
NANDroid → A set of tools that will enable anyone who has root on their Android device to make FULL system backups, in case something goes wrong or you want to try out that new experimental ROM/theme. NANDroid will backup (and restore) /system, /data, /cache, and /boot partitions.
Recovery Mode → A special environment that you can boot into for troubleshooting and upgrading purposes.
Kang → The process of creating a code based of someone else's code or reapplying code that someone else created into your own code (e.g. git cherry-pick)
Rooting → is a process that allows users of mobile phones and other devices running the Android operating system to attain privileged control (known as "root access") within Android's Linux subsystem with the goal of overcoming limitations that carriers and manufacturers put on some devices.
Click to expand...
Click to collapse
thanks.. there were a few in there I didn't know!
FYI, I'm fairly certain appdroid kanged this from the CyanogenMod wiki.

Rooting

Do Not Post Question in General Post in Q&A CLOSED
I'm not super educated, but I'm pretty sure I can explain the fundamentals of it (correct me if I'm wrong anyone)...
The Android operating systems runs ontop of a linux kernel... and just like any other linux distribution, there is a particular set of low level system files that you, the user, by default, don't have access too. This is to prevent you from breaking anything, as well as to prevent malicious software/intruders to compromise the security of your file system.
These same low level system files, however, are useful for many things. In order to make changes to a lot of things (overclock your processor, tweak speed and battery life, sometimes sideload applications outside the market; although most devices let you do this without rooting now, and in most cases install a non-stock system image).
This system image is known as a ROM; a rom can be pulled from another device and then modified to work on your own, or in some cases can be an original release from Google (Known as an AOSP) which is then 'cooked' by a developer to work on your device.
If you're familiar with reinstalling or installing Windows, it's a pretty easy concept. Once a device is rooted, a custom recovery can be flashed to the device. This custom recovery allows you to flash over your stock system image with a new ROM.
Rooting is basically taking control over your device for what can be installed, deleted, or altered.
Here is a link to give you much more info on rooting:
http://m.androidcentral.com/what-rooting

[INFO]Android Terms,Slang & Definitions

I found a very usefull thread. So i think it might be usefull here.
Original thread: http://forum.xda-developers.com/showthread.php?p=21856647#post21856647
Diablo67 said:
Check out this vid,this is the reason for my thread...
http://youtu.be/RzpixaIOwSg
I figured i would post this thread to help all of the new members and experienced understand the Android slang,there are actually a few i did'nt know the meaning of until i made this thread.I have compiled most of the terms,definitions and slang i could dig up,if theres anything i missed,let me know and i will add it to the thread,otherwise i will update this thread as new slang,terms and definitions are presented to me.
Apps2SD:A method of storing applications and cache on the device's microSD card.
ADB:Android Debug Bridge (adb) is a versatile command line tool that lets you communicate with an emulator instance or connected Android-powered device. It is a client-server program that includes three components:
•A client, which runs on your development machine. You can invoke a client from a shell by issuing an adb command. Other Android tools such as the ADT plugin and DDMS also create adb clients.
•A server, which runs as a background process on your development machine. The server manages communication between the client and the adb daemon running on an emulator or device.
•A daemon, which runs as a background process on each emulator or device instance.
Android:A Linux-based operating system for mobile devices such as HTC EVO.Versions are alphabetically codenamed after snacks: Donut, Eclair, Froyo, Gingerbread, Honeycomb, Ice Cream Sandwich, Jelly Donut.
AMOLED:Active Matrix Organic Light Emitting Diode. Basically, a very colorful, bright, display found in some smartphones.
APK:Android application package file. Each Android application is compiled and packaged in a single file that includes all of the application's code (.dex files), resources, assets, and manifest file. The application package file can have any name but must use the .apk extension. For example: myExampleAppname.apk. For convenience, an application package file is often referred to as an ".apk".
Alpha:The alpha phase of the release life cycle is the first phase to begin software testing (alpha is the first letter of the Greek alphabet, used as the number 1). In this phase, developers generally test the software using white box techniques. Additional validation is then performed using black box or gray box techniques, by another testing team. Moving to black box testing inside the organization is known as alpha release.[1]
Alpha software can be unstable and could cause crashes or data loss. The exception to this is when the alpha is available publicly (such as a pre-order bonus), in which developers normally push for stability so that their testers can test properly. External availability of alpha software is uncommon in proprietary software. However, open source software, in particular, often have publicly available alpha versions, often distributed as the raw source code of the software.
The alpha phase usually ends with a feature freeze, indicating that no more features will be added to the software. At this time, the software is said to be a feature complete.
Boot Animation:Boot animation is a term for a graphical representation of the boot process of the operating system.
Boot animation can be a simple visualisation of the scrolling boot messages in the console, but it can also present graphics or some combinations of both.
Unlike splash screens, boot screen or boot animation is not necessarily designed for marketing purposes, but can be to enhance the experience of the user as eye candy, or provide the user with messages (with an added advantage of color coding facility) to diagnose the state of the system.
Bootloader:This small program's only job is to load other data and programs which are then executed from RAM.Often, multiple-stage boot loaders are used, during which several programs of increasing complexity load one after the other in a process of chain loading.
Bootloop:When your system recycles over and over without entering the main OS.
Beta: is the software development phase following alpha. It generally begins when the software is feature complete. Software in the beta phase will generally have many more bugs in it than completed software, as well as speed/performance issues. The focus of beta testing is reducing impacts to users, often incorporating usability testing. The process of delivering a beta version to the users is called beta release and this is typically the first time that the software is available outside of the organization that developed it.
The users of a beta version are called beta testers. They are usually customers or prospective customers of the organization that develops the software, willing to test the software without charge, often receiving the final software free of charge or for a reduced price.
Beta version software is often useful for demonstrations and previews within an organization and to prospective customers. Some developers refer to this stage as a preview, prototype, technical preview (TP), or early access.
Some software is kept in perpetual beta—where new features and functionality is continually added to the software without establishing a firm "final" release.
CPU:It stands for Central Processing Unit and handles all the complex mathematical formulas necessary to do everyday things like surfing the Internet.
Custom:Independent developers who like to customize their devices beyond the standard options provided often tend to release the fruits of their labor for the rest to enjoy, in form of custom ROMs.
Cache:A component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere. If requested data is contained in the cache (cache hit), this request can be served by simply reading the cache, which is comparatively faster. Otherwise (cache miss), the data has to be recomputed or fetched from its original storage location, which is comparatively slower. Hence, the greater the number of requests that can be served from the cache, the faster the overall system performance becomes.
CDMA:Mobile phone standards called cdmaOne, CDMA2000 (the 3G evolution of cdmaOne) and WCDMA (the 3G standard used by GSM carriers), which are often referred to as simply CDMA, and use CDMA as an underlying channel access method.
CIQ:Carrier IQ. A piece of preinstalled software that runs with elevated access in the background of portable devices by default and records everything. Potentially can be exploited to steal information.
Dual Core:A dual core processor is a central processing unit (CPU) that has two separate cores on the same die, each with its own cache. It essentially is two microprocessors in one. This type of CPU is widely available from many manufacturers. Other types of multi-core processors also have been developed, including quad-core processors with four cores each, hexa-core processors with six, octa-core processors with eight and many-core processors with an even larger number of cores.
Dalvik:The Android platform's virtual machine. The Dalvik VM is an interpreter-only virtual machine that executes files in the Dalvik Executable (.dex) format, a format that is optimized for efficient storage and memory-mappable execution.
Dalvik Cache:Writable cache that contains the optimized bytecode of all apk files (apps) on your Android device. Having the information in it's own cache makes applications load faster and perform better.
EXT2:The ext2 or second extended filesystem is a file system for the Linux kernel. It was initially designed by Rémy Card as a replacement for the extended file system (ext).
ext2 was the default filesystem in several Linux distributions, including Debian and Red Hat Linux, until supplanted more recently by ext3, which is almost completely compatible with ext2 and is a journaling file system. ext2 is still the filesystem of choice for flash-based storage media (such as SD cards, and USB flash drives) since its lack of a journal minimizes the number of writes and flash devices have only a limited number of write cycles. Recent kernels, however, support a journal-less mode of ext4, which would offer the same benefit along with a number of ext4-specific benefits.
EXT3:Third extended filesystem, is a journaled file system that is commonly used by the Linux kernel. It is the default file system for many popular Linux distributions, including Debian. Stephen Tweedie first revealed that he was working on extending ext2 in Journaling the Linux ext2fs Filesystem in a 1998 paper and later in a February 1999 kernel mailing list posting, and the filesystem was merged with the mainline Linux kernel in November 2001 from 2.4.15 onward.Its main advantage over ext2 is journaling, which improves reliability and eliminates the need to check the file system after an unclean shutdown. Its successor is ext4.
EXT4:It was born as a series of backward compatible extensions to ext3, many of them originally developed by Cluster File Systems for the Lustre file system between 2003 and 2006, meant to extend storage limits and add other performance improvements.However, other Linux kernel developers opposed accepting extensions to ext3 for stability reasons,and proposed to fork the source code of ext3, rename it as ext4, and do all the development there, without affecting the current ext3 users. This proposal was accepted, and on 28 June 2006, Theodore Ts'o, the ext3 maintainer, announced the new plan of development for ext4.
FC/FC's:Short for "force close," meaning an app that has crashed.
Fastboot:A diagnostic protocol used primarily to modify the flash filesystem in Android smartphones from another computer over a USB connection. It is part of the Android Debug Bridge library.
Utilizing the Fastboot protocol requires that the device be started in a boot loader or Second Program Loader mode in which only the most basic hardware initialization is performed. After enabling the protocol on the device itself it will accept any command sent to it over USB via a command line. Some of most commonly used fastboot commands include:
•flash - Overwrites a partition in flash with a binary image stored on the host computer.
•erase - Erases a partition in flash.
•reboot - Reboots the device into the either the main operating system or the system recovery partition.
•devices - Displays a list of all devices (with Serial #) connected to the host computer.
Flashing:The ROM memory used in smartphones and tablets etc. is often same as flash memory found in SD cards and USB flash drives, simply optimized for better speed and performance while running the operating system.
Hotspot:A spot that offers Internet access over a wireless local area network through the use of a router connected to a link to an Internet service provider. Hotspots typically use Wi-Fi technology.You can connect wifi campatible devices to it.
HDMI:High-Definition Multimedia Interface) is a compact audio/video interface for transmitting encrypted uncompressed digital data.It is a digital alternative to consumer analog standards, such as radio frequency (RF) coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA (also called D-sub or DE-15F). HDMI connects digital audio/video sources (such as set-top boxes, DVD players, HD DVD players, Blu-ray Disc players, AVCHD camcorders, personal computers (PCs), video game consoles (such as the PlayStation 3 and Xbox 360), AV receivers, tablet computers, and mobile phones) to compatible digital audio devices, computer monitors, video projectors, and digital televisions.
Hboot:It’s mainly responsible for checking and initializing the hardware and starting the phone’s software. It can also be used for flashing official software releases, as well as a few other things. HBoot can be compared to the BIOS on a computer.
HAVS:a control system that dynamically adjusts the voltage based on CPU load. This has proven to be a battery saver, but it can actually have the opposite effect when multiple control systems are operating (like setCPU).
JIT:The Just-in-Time Compiler. Released with Android 2.2, it's a method of greatly speeding up apps in Android on the software side.
Kang:Someone writes a code,someone else modifies the code to make their own release,its concidered a kang release.
Kernel:A kernel is a layer of code that allows the OS and applications to interface with your phone's hardware. The degree in which you can access your phone's hardware features depends on the quality of code in the kernel. The homebrew (rooting) community for HTC has made several kernel code improvements that give us additional features from our hardware that the stock kernel does not. When you flash a custom ROM, you automatically get a kernel. But you can also flash a standalone kernel ROM on top of the existing one, effectively overwriting it. These days, the difference in custom kernels is less about new features and more about alternate configurations. Choosing a custom kernel is basically choosing one that works best with your ROM.
Launcher:Collectively, the part of the Android user interface on home screens that lets you launch apps, make phone calls, etc. Is built in to Android, or can be purchased in the Android Market.
LCD Density:Pixel density is a measurement of the resolution of devices in various contexts; typically computer displays, image scanners, and digital camera image sensors.
First of all you need to understand that the Android User Interface uses something called a "display independent pixel" or a "dip" (yes, it's confusing because the density settings are in "dots per inch" or "dpi" which are considered the same as "ppi" or "pixels per inch" as well).
The default LCD Density setting on Android is 160 dpi. As far as the operating system is concerned 1 dip @ 160 dpi = 1 screen pixel. It doesn't mean that's actually true, but you've gotta start somewhere. In my opinion it would have been a lot nicer if they'd chosen 100 dpi because then it would be an easy percentage thing, but they didn't so we're stuck with this formula.
Mod:The act of modifying a piece of hardware or software or anything else for that matter, to perform a function not originally conceived or intended by the designer.
Nandroid:To backup the current running rom.
Nightly:A build that is performed at the end of each day of development. If you use a continuous integration server, it will generally be configured to build the code and run the unit tests on every check in. At the end of each day you may want to run more extensive tests, regression test and integration tests for example, which take too long to run on each check in and these would be triggered after the nightly build. If you have a full continuously delivery pipeline the nightly build may also be used to deploy the built code to environments for user testing.
Open GL:An open source 3D graphics library used in many devices, including Android devices.
Open & Closed Beta:Developers release either a closed beta or an open beta; closed beta versions are released to a select group of individuals for a user test and are invitation only, while open betas are from a larger group to the general public and anyone interested. The testers report any bugs that they find, and sometimes suggest additional features they think should be available in the final version.
Overclock:To increase the speed of your CPU.
Partition:The phone's internal memory (not the SD card) is solid-state (flash) memory, AKA NAND. It can be partitioned much like a normal hard drive can be partitioned. The bootloader exists in its own partition. Recovery is another partition; radio, system, cache, etc are all partitions.
Here are the standard partitions on an Android phone:
/misc - not sure what this is for.
/boot - bootloader, kernel
/recovery - holds the recovery program (either clockworkmod or RA recovery for a rooted Evo)
/system - operating system goes here: Android, Sense, boot animation, Sprint crapware, busybox, etc
/cache - cached data from OS usage
/data - user applications, data, settings, etc.
The below partitions are not android-specific. They are tied to the hardware of the phone, but the kernel may have code allowing Android to interact with said hardware.
/radio - the phone's radio firmware, controls cellular, data, GPS, bluetooth.
/wimax - firmware for Sprint's flavor of 4G, WiMax.
PRL:The Preferred Roaming List, basically a way of telling your phone which towers to connect to first.
RUU:a complete software package released by HTC, it can contain many things they are trying to update. Radio, ROM, bootloader, etc... Installing an ruu is like installing an image on a hard drive it wipes the phone and installs the image. It will wipe everything data and all so if you install one be prepared.
Recovery Mode:A small separate operating mode you can boot your device into, used for device administration. Two popular custom recovery modes are Amon Ra and Clockwork.
Rom/Firmware:Read-Only Memory and technically speaking, it refers to the internal storage of a device, which is supposed to contain the operating system instructions that needn’t be modified at all during the device’s normal operation.
Radios:On the HTC side of things,the radios persist of:
•WiFi, which operates at 2.4-5ghz depending on what channel it's running
•Cellular/3G, which carries voice and data
•4G/WiMAX, which only carries data
•GPS, which is receive-only
•Bluetooth, which talks to WiiMotes and headsets
Flashing a radio means updating the code that controls the phones way of sending and recieving a signal.
Ram:(Random Access Memory) A group of memory chips, typically of the dynamic RAM (DRAM) type, which function as the computer's primary workspace. When personal computers first came on the market in the late 1970s, 64KB (64 kilobytes) of RAM was the upper limit. Today, 64MB (64 megabytes) of SDRAM is entry level for a desktop computer, a thousand times as much (see SDRAM).
The "random" in RAM means that the contents of each byte of storage in the chip can be directly accessed without regard to the bytes before or after it. This is also true of other types of memory chips, including ROMs and PROMs. However, unlike ROMs and PROMs, RAM chips require power to maintain their content, which is why you must save your data onto disk before you turn the computer off. To learn about the types of RAM chips and how to upgrade your memory, see memory module. To learn how memory is used to process data, see computer or memory. See also dynamic RAM and static RAM.
Recovery:RecoverySystem contains methods for interacting with the Android recovery system (the separate partition that can be used to install system updates,wipe user data,etc).
Root:The first level of a folder.
Rooting:A process allowing users of mobile phones, tablet PCs, and other devices running the Android operating system to attain privileged control (known as "root access") within Android's subsystem. Rooting is often performed with the goal of overcoming limitations that carriers and hardware manufacturers put on some devices, resulting in the ability to alter or replace system applications and settings, run specialized apps that require administrator-level permissions, or perform other operations that are otherwise inaccessible to a normal Android user. Rooting is analogous to jailbreaking devices running the Apple iOS operating system or the Sony PlayStation 3. On Android, rooting can also facilitate the complete removal and replacement of the device's operating system.
SBC:(the ability to charge your battery beyond the default safe limit). The concept is similar to overclocking a processor: you're overriding the safety limits established to achieve additional performance. The benefit here is that you may gain more use of your battery per charge. The drawback is that you can damage the battery and significantly reduce its longevity. Some kernels claim they are using a safe technique to prevent battery damage. Just be aware of the potential risks.
Sideloading:It means installing applications without using the official Android Market.
Splash Screen:A splash screen is an image that appears while android is loading.Splash screens cover the entire screen or simply a rectangle near the center of the screen. The splash screens of operating systems and some applications that expect to be run full-screen usually cover the entire screen.
Superuser/SU:On many computer operating systems, the superuser is a special user account used for system administration. Depending on the operating system, the actual name of this account might be: root, administrator or supervisor.
Normal work on such a system is done using ordinary user accounts, and because these do not have the ability to make system-wide changes any viruses and other malware - or simple user errors - do not have the ability to adversly affect a whole system. In organizations, administrative privileges are often reserved for authorized experienced individuals.
Script:The Scripting Layer for Android (abridged as SL4A, and previously named Android Scripting Environment or ASE) is a library that allows the creation and running of scripts written in various scripting languages directly on Android devices. SL4A is designed for developers and is still alpha quality software.
These scripts have access to many of the APIs available to normal Java Android applications, but with a simplified interface. Scripts can be run interactively in a terminal, in the background, or via Locale.
SDK:(SDK or "devkit") is typically a set of software development tools that allows for the creation of applications for a certain software package, software framework, hardware platform, computer system, video game console, operating system, or similar platform.
Stock:This is the operating system in its default form, without any modifications made to it except for any device-specific support required to run it on the particular device.
S-On:Security on,means no acces to the phones operating system.
S-Off:Security was exploited,now have access to the operating system.
Tethering:Means sharing the Internet connection of an Internet-capable mobile phone with other devices. This sharing can be offered over a wireless LAN (Wi-Fi), Bluetooth, or by physical connection using a cable. In the case of tethering over wireless LAN, the feature may be branded as a mobile hotspot.The Internet-connected mobile phone acts as a portable router when providing tethering services to others.
Underclock:To reduce the speed of your CPU.
Undervolt:Undervolting means taking some of the voltage from the CPU which in return gives a longer battery life and lower temperature during intensive use of the CPU.
USB:Stands for Universal Serial Bus. Is a method of connecting devices to a computer. Most smartphones now use microUSB cables to charge and sync.
Updater Script:When Android devices install updates via 'update.zip' files using recovery mode they have to perform a wide range of functions on files and permissions. Instead of using a minimal shell such as {b,d,c}sh the Android designers decided to create a small functional language that can be extended by device manufacturers if necessary. Since the Android "Donut" release (v1.6) the scripting language is called Edify and is defined primarily in the bootable/recovery/{edify,edifyscripting,updater} directories of the Android source-code tree.
Wireless N:Wireless N technology increases wireless internet connection. Wireless 'N' routers also work with Wireless 'G' and 'B' wireless adapters.
WiiMax:(Worldwide Interoperability for Microwave Access) is a communication technology for wirelessly delivering high-speed Internet service to large geographical areas.
YAFFS:Yaffs1 is the first version of this file system and works on NAND chips that have 512 byte pages + 16 byte spare (OOB;Out-Of-Band) areas.[clarification needed] These older chips also generally allow 2 or 3 write cycles per page,which YAFFS takes advantage of - i.e. dirty pages are marked by writing to a specific spare area byte.
Newer NAND flash chips have larger pages, 2048 bytes + 64 bytes spare areas, and stricter write requirements.Each page within an erase block (128 kilobytes) must be written to in sequential order, and each page must be written only once.YAFFS2 was designed to accommodate these newer chips.YAFFS2 is based on the YAFFS1 source code,with the major difference being that internal structures are not fixed to assume 512 byte sizing,and a block sequence number is placed on each written page. In this way older pages can be logically overwritten without violating the "write once" rule.[clarification needed]
YAFFS is a robust log-structured file system that holds data integrity as a high priority.A secondary YAFFS goal is high performance.YAFFS will typically outperform most alternatives.It is also designed to be portable and has been used on Linux, WinCE, pSOS, eCos,ThreadX and various special-purpose OSes.A variant 'YAFFS/Direct' is used in situations where there is no OS, embedded OSes and bootloaders: it has the same core filesystem but simpler interfacing to the OS and NAND flash hardware.
Zipalign: An archive alignment tool introduced first time with 1.6 Android SDK (software development kit). It optimizes the way an Android application package (APK) is packaged. Doing so enables the Android operating system to interact with the application more efficiently, and hence has the potential to make the application and overall the whole system much faster. Execution time is minimized for zipaligned applications, resulting is lesser amount of RAM consumption when running the APK.
Click to expand...
Click to collapse
Thans man;i thing and this is useful:
Let’s start with a list of standard internal memory partitions on Android phones and tablets. These are:
/boot
/system
/recovery
/data
/cache
/misc
In addition, there are the SD card partitions.
/sdcard
/sd-ext
Note that only /sdcard is found in all Android devices and the rest are present only in select devices. Let’s now take a look at the purpose and contents of each of these partitions.
/boot
This is the partition that enables the phone to boot, as the name suggests. It includes the kernel and the ramdisk. Without this partition, the device will simply not be able to boot. Wiping this partition from recovery should only be done if absolutely required and once done, the device must NOT be rebooted before installing a new one, which can be done by installing a ROM that includes a /boot partition.
/system
This partition basically contains the entire operating system, other than the kernel and the ramdisk. This includes the Android user interface as well as all the system applications that come pre-installed on the device. Wiping this partition will remove Android from the device without rendering it unbootable, and you will still be able to put the phone into recovery or bootloader mode to install a new ROM.
/recovery
The recovery partition can be considered as an alternative boot partition that lets you boot the device into a recovery console for performing advanced recovery and maintenance operations on it. To learn more about this partition and its contents, see the ‘About Android Recovery’ section of our guide to ClockworkMod recovery.
/data
Also called userdata, the data partition contains the user’s data – this is where your contacts, messages, settings and apps that you have installed go. Wiping this partition essentially performs a factory reset on your device, restoring it to the way it was when you first booted it, or the way it was after the last official or custom ROM installation. When you perform a wipe data/factory reset from recovery, it is this partition that you are wiping.
/cache
This is the partition where Android stores frequently accessed data and app components. Wiping the cache doesn’t effect your personal data but simply gets rid of the existing data there, which gets automatically rebuilt as you continue using the device.
/misc
This partition contains miscellaneous system settings in form of on/off switches. These settings may include CID (Carrier or Region ID), USB configuration and certain hardware settings etc. This is an important partition and if it is corrupt or missing, several of the device’s features will will not function normally.
/sdcard
This is not a partition on the internal memory of the device but rather the SD card. In terms of usage, this is your storage space to use as you see fit, to store your media, documents, ROMs etc. on it. Wiping it is perfectly safe as long as you backup all the data you require from it, to your computer first. Though several user-installed apps save their data and settings on the SD card and wiping this partition will make you lose all that data.
On devices with both an internal and an external SD card – devices like the Samsung Galaxy S and several tablets – the /sdcard partition is always used to refer to the internal SD card. For the external SD card – if present – an alternative partition is used, which differs from device to device. In case of Samsung Galaxy S series devices, it is /sdcard/sd while in many other devices, it is /sdcard2. Unlike /sdcard, no system or app data whatsoever is stored automatically on this external SD card and everything present on it has been added there by the user. You can safely wipe it after backing up any data from it that you need to save.
/sd-ext
This is not a standard Android partition, but has become popular in the custom ROM scene. It is basically an additional partition on your SD card that acts as the /data partition when used with certain ROMs that have special features called APP2SD+ or data2ext enabled. It is especially useful on devices with little internal memory allotted to the /data partition. Thus, users who want to install more programs than the internal memory allows can make this partition and use it with a custom ROM that supports this feature, to get additional storage for installing their apps. Wiping this partition is essentially the same as wiping the /data partition – you lose your contacts, SMS, market apps and settings.
Here is original treath:http://www.addictivetips.com/mobile...plained-boot-system-recovery-data-cache-misc/
and this:http://www.addictivetips.com/mobile...-and-how-to-use-it-on-android-complete-guide/
Nice..
And i get the 3rd post..
I think that jelly donut, called to jelly bean
Sent from my Neo V with supercharged ICS ^^

RFC: Android boot environments, advice and comments please

OK, I am starting this thread for a general discussion related to some development work I am currently doing. It involves some fairly low level components of the Android architecture.
I am basing this on CM9, CM being my preferred flavour of Android, but it applies to other flavours too. It will be developed first for an Allwinner A10 tablet (A Momo9 clone) as this is the least important Android device I have lying around, the one which I am least bothered about breaking, but I plan to make these updates as generic as possible to allow easy porting.
OK, on to my objectives:
Make a flexible boot environment system, allowing a device to be booted into different ROMs/configurations, using LVM as a base. This would also allow more flexible use of internal memory, snapshots, and non-persistent data configurations.
*EDIT* By the way, the first part of this (getting LVM2 onto Android) has been completed already by steven676 (see his github repo)
Make additions to CWM recovery to allow management of LVM volumes and boot environments. I have no idea where to start on this one, seeing as I can't even find the source for CWM, but it is necessary to make the project work well.
Make additions to vold and the Android storage settings to allow management of volumes and boot environments from within Android, and to recognise logical volumes for use as internal "SD card". This will probably have to be accomplished using an additional daemon due to license incompatibilities between vold (Apache) and LVM (GPL), but I would like the main interface to my work to be within vold as it is the logical place.
The idea would be that you create an LVM volume group using your internal storage (probably system, data, cache and internal SD partitions), and then define your sys/data/cache/sd etc. as logical volumes within this group. As stated above in objective 1, this gives you flexibility (you can size them as you wish) and access to the snapshot functionality. Snapshots would be great in testing software (you can easily get your device back to a known good config), and would also allow a non-persistent configuration (all changes discarded on reboot, great for handing a device to another person e.g. your kids).
The reason I wish to do this is as a base for my next project, which needs the kind of flexibility this will bring, but I want to keep this discussion on track, so I wont muddy the waters with the details of it yet. However, it will also aid those with small system partitions, developers, and those with small children (or partners... ) who install loadsa rubbish and screw up your device.
The mods I plan to make in CWM should also make it much easier to make update packages for different devices, as I plan to include methods for the updater-script to determine where things should be going (where the system/data/boot etc. devices live), rather than having to hard code them in the script.
So: Thoughts? Advice? Please don't just leave comments of "This is a good/bad idea", I am looking for a constructive discussion.
Thanks in advance
Mouse
I'm not quite following you. Are you planing to boot from an LVM volume? If so, you'll more or less require GRUB2, and does GRUB2 support ATAGS? I believe you'll need 'em both for this to succeed.
Hi
Not quite.
The plan is to use the standard Android boot mechanism to load the kernel and initrd. Within this initrd, the mounting of filesystems (system/data/cache etc) is moved into a separate daemon which chooses them from LVM (or anywhere really). This is limitted, of course, to using just one kernel & initrd (unless kexec can be used, which is beyond the scope of what I need for this project), but it allows much greater flexibility.
drmouse81 said:
The plan is to use the standard Android boot mechanism to load the kernel and initrd. Within this initrd, the mounting of filesystems (system/data/cache etc) is moved into a separate daemon which chooses them from LVM (or anywhere really). This is limitted, of course, to using just one kernel & initrd (unless kexec can be used, which is beyond the scope of what I need for this project), but it allows much greater flexibility.
Click to expand...
Click to collapse
Ah, ok, you are making it easy for you. I do something similar myself. After I boot my custom initramfs, it performs a switchroot to the SDcard, continuing the execution of the real init there. This gives about the same flexibility you are seeking, but also with the same limitation the kernel must stay the same for all systems. This way I can change the system by replacing the SDcard, without the need of LVM.
Yes, this is very similar to what I am in the process of doing. I just think that, especially in devices with large amounts of internal storage (my tab has 16GB) as well as an SD card slot, LVM is a much more flexible solution. Snapshots are the main benefit, but I also plan to use LVM for another project.
Really, the LVM part is pretty simple. The project mentioned on github has the majority of the work done, I am simply extending it at the moment to include some additional features. The majority of the work involved here will be integrating it more closely with both Android and CWM (I expect a steep learing curve: I already develop in both C/C++ and Java, but am not very familliar with the internal workings of Android, and can't even find the sources for CWM).
I do believe it is worth the effort, however. Who knows, it may even make it into CM, or even official Android, at some point... Doubt it, but it is possible

[Q] Android RAM-terms and explanation?

Hi I wanted to see what you guys make of these apps. Does anyone know where I could get a reference guide specifically pertaining to such apps.
Even the "Performance control" feature found in most AOPK Custom Rom's have these weird terms.
Any help would be great.
Here's a picture for reference...sorta
WestxtseW said:
Hi I wanted to see what you guys make of these apps. Does anyone know where I could get a reference guide specifically pertaining to such apps.
Even the "Performance control" feature found in most AOPK Custom Rom's have these weird terms.
Any help would be great.
Here's a picture for reference...sorta
Click to expand...
Click to collapse
init.d -- a system that allows for running services at boot that are not run by the init.rc scripts
swap -- virtual memory. unlike ram, swap is stored on disk/flash storage, and as a result is slower but larger.
dirty -- memory that may need to be written to disk/flash. consider it used.
soft reboot -- a reboot that only restarts high-level system functions (essentially, the android part of android rather than the linux part)
couldn't tell you about the other options in android tweaker. see if it has a help file or similar.
hope it helps!
--ultraviolet
ultravioletnanokitty said:
init.d -- a system that allows for running services at boot that are not run by the init.rc scripts
swap -- virtual memory. unlike ram, swap is stored on disk/flash storage, and as a result is slower but larger.
dirty -- memory that may need to be written to disk/flash. consider it used.
soft reboot -- a reboot that only restarts high-level system functions (essentially, the android part of android rather than the linux part)
couldn't tell you about the other options in android tweaker. see if it has a help file or similar.
hope it helps!
--ultraviolet
Click to expand...
Click to collapse
Thanks! :good: that's pretty much what I'm looking for; leads that help me get my mind around it a bit more
iglo a109 problem
se.. all of those aren`t checked, when i tried to connect, in the photo, they are like that because it was i made a mistake when i created the print screen, so... i don't see how that's the problem, when i connect my phone and then after 2 sec it disconnects itself and starts charging

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