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doc:techref:bootloader [2013/07/03 19:39]
lorema
doc:techref:bootloader [2015/04/26 08:57] (current)
theoradicus fix link
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 The [[wp>​Bootloader]] is a piece of software that is executed every time the hardware device is powered up. It is executable machine code and thus [[doc/​hardware/​cpu#​the.isa.instruction.set.architecture|ARCH]]-specific. It's quite heavily device-specific because its main task is to initialize all the low-level hardware details. The bootloader can be contained on a separate [[wp>​EEPROM]] (very seldom) or directly on flash storage (most common). The [[wp>​Bootloader]] is a piece of software that is executed every time the hardware device is powered up. It is executable machine code and thus [[doc/​hardware/​cpu#​the.isa.instruction.set.architecture|ARCH]]-specific. It's quite heavily device-specific because its main task is to initialize all the low-level hardware details. The bootloader can be contained on a separate [[wp>​EEPROM]] (very seldom) or directly on flash storage (most common).
  
-| {{:​meta:​icons:​tango:​dialog-information.png?​nolink}} | Being a piece of software, the bootloader is considered part of the firmware, but <color red>​**the bootloader is not part of OpenWrt!**</​color>​\\ Only on seldom occasions a change of the //​bootloader settings// or the //​bootloader code// is necessary to allow for booting/​installing OpenWrt\\ There are a number of bootloaders under diverse [[wp>​software license]]s ​|+<WRAP round tip> 
 +Being a piece of software, the bootloader is considered part of the firmware, but <color red>​**the bootloader is not part of OpenWrt!**</​color>​\\ Only on seldom occasions a change of the //​bootloader settings// or the //​bootloader code// is necessary to allow for booting/​installing OpenWrt\\ There are a number of bootloaders under diverse [[wp>​software license]]s 
 +</​WRAP>​
  
 ===== Main Function ===== ===== Main Function =====
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     * once the bootloader has fulfilled its main function - chainload the Kernel - it does not run any longer, so to play with it, you have to login to it before it loads the Kernel and you may also have to prevent it from loading the Kernel, i.e. to stop the boot process.     * once the bootloader has fulfilled its main function - chainload the Kernel - it does not run any longer, so to play with it, you have to login to it before it loads the Kernel and you may also have to prevent it from loading the Kernel, i.e. to stop the boot process.
   * boot from USB   * boot from USB
-    * Like the Kernel requires the module ''​kmod-fs-ext4''​ to read/write to a EXT3 filesystem, so a bootloader requires such a module to do the same. [[wp>​GRUB2]] has this functionality implemented,​ so with it, you can very comfortably configure your boot options and also update and maintain your OS. The lightweight bootloaders we use with OpenWrt, usually do not have this functionality. But see [[doc:​techref:​Flash Layout]] for further reference. One exception is the U-Boot implementation of the [[toh:​seagate:​dockstar]]. It can not only initialize the USB (like all the rest of the hardware) but additionally utilize the USB and also understand the EXT2 filesystem. Thus, the dockstar can be booted directly from an ext2-formated harddisc/​usb-stick connected to any of it's USB-ports.+    * Like the Kernel requires the module ''​kmod-fs-ext4''​ to read/write to a EXT3 filesystem, so a bootloader requires such a module to do the same. [[wp>​GRUB2]] has this functionality implemented,​ so with it, you can very comfortably configure your boot options and also update and maintain your OS. The lightweight bootloaders we use with OpenWrt, usually do not have this functionality. But see [[doc:​techref:​flash.layout]] for further reference. One exception is the U-Boot implementation of the [[toh:​seagate:​dockstar]]. It can not only initialize the USB (like all the rest of the hardware) but additionally utilize the USB and also understand the EXT2 filesystem. Thus, the dockstar can be booted directly from an ext2-formated harddisc/​usb-stick connected to any of it's USB-ports.
   * [[inbox:​netboot|net booting]] functionality via [[wp>​Bootstrap Protocol|BOOTP]] or [[wp>​Preboot Execution Environment|PXE]] or DHCP or NFS or [[wp>​Trivial File Transfer Protocol|TFTP]]   * [[inbox:​netboot|net booting]] functionality via [[wp>​Bootstrap Protocol|BOOTP]] or [[wp>​Preboot Execution Environment|PXE]] or DHCP or NFS or [[wp>​Trivial File Transfer Protocol|TFTP]]
  
doc/techref/bootloader.1372873161.txt.bz2 · Last modified: 2013/07/03 19:39 by lorema