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CILO - CiscoLoad Sane Bootloader for real ELF Files
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1. What is this?
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CILO, or CiscoLoad is a ROMMON bootloader replacement for Cisco Routers.
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The ROMMON bootloader will load CILO, which then can be used to boot IOS
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or an alternative operating system.
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2. Why do I need this?
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The ROMMON bootloader is extremely broken -- it is only capable of
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understanding a single ELF segment in an ELF file. Of course, because Linux
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and other operating systems rely fairly heavily on being able to have more
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than one segment in the output ELF file, this clearly isn't acceptable.
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CiscoLoad works around this by providing an ELF file that looks somewhat
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like an IOS image to ROMMON; from CiscoLoad, it is then possible to load an
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arbitrary standalone ELF file, such as a kernel image, or even an IOS image.
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3. How do I build CILO?
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Assuming you have a mips-elf toolchain installed (how to do this is beyond
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the scope of this document, but it should be simple to do. Just remember the
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target architecture is mips-elf and not mips-unknown-linux-gnu), just go
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to the root directory of the source distribution and type make. Everything
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should build from there.
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Copy the ciscoload.bin file to the router's flash along with your kernel and
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set the router boot image to be ciscoload.bin.
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4. How do I use CILO?
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Assuming you have one of the supported routers, it is really quite easy.
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In short, you must build CiscoLoad and a kernel then copy them to your
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device's flash, typically using IOS.
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When the router boots, it will load CILO; CILO then will prompt you to
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select the file you want to boot. Enter the file name you wish to boot, and
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away you go!
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5. What hardware is supported?
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At this time, the Cisco 3600 Series of routers (3620 and 3640 at least) are
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very well supported. As well, preliminary support is underway for the
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Cisco 1700 Series routers.
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6. What is ELFTool?
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ELFTool is a small app that can be used to analyze ELF32 files. It is used
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as a test case for the elf.h header and the ELF reading support in
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CiscoLoad. To build it, go to the elftool/ directory in the source dist-
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ribution, and type make.
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7. Who wrote CiscoLoad?
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CiscoLoad was the result of many wasted hours of Phil Vachon, who can be
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reached at philippe@cowpig.ca.
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The printf function was gracelessly lifted from the Linux Kernel.
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8. What License is CiscoLoad shipped under
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While CiscoLoad is a simple piece of software, the code is covered under the
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GNU General Public License version 2.
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