Difference between revisions of "Netboot-scratchpad"
From Funtoo Linux
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</pre> | </pre> | ||
| − | * Recompile a Linux kernel and put the modules in the cramfs directory | + | * Recompile a Linux kernel and put the modules in the cramfs directory structure (make modules_install INSTALL_MOD_PATH=/path/to/ramdisk/tree) |
| − | + | ** Don't forget to put a default argument init=... (if is is suitable to keet the init deployed by busybox as is) | |
| − | * put something useful in /bin/ | + | ** Put something useful in the cutomized init (can be a script) like |
| + | <pre> | ||
| + | #!/bin/ash | ||
| + | echo "Hello world" | ||
| + | </pre> | ||
| + | * Build the cramfs, name it root.img and put it in /usr/src | ||
| + | * Build the tftpboot image => cd /usr/src/linux && make tftpboot.img | ||
| + | * Put the image on a tftpserver | ||
[[Category:Labs]] | [[Category:Labs]] | ||
Revision as of 02:40, 8 February 2011
Draft for an experiment in progress. Accuracy here is random!
Contents |
Warning
Information here may vary from day to day and hour to hour. It is a "pad" to help us to take various notes on a future and more complete tutorial on how produce netboot images for SPARC machines. Free feel to annotate if you wish.
Tools
- Tilo (seems a bit buggy especially with large image => segfaults)
- Linux kernel in itself
The Linux kernel way
- Magic command (/in /usr/src/linux) : make tftpboot.img
- Scans System.map to get ELF entries (espcially _star and _end)
- Requires a root.img file in /usr/src. This file is a ramdisk image (!= initrd ?). The smaller the better, so cramfs can be used therem of course busybox is required.
- cramfs must be included built-in
- Some Sun machines does not initialize their MMU so everything must fit in 4 Mb in their case (1 page)
Cramfs
- Designed for having a small footprint, ideal (to check with rw mount points ? The Fs is readonly and limited around 272Mb in size, no possibility to remount it rw...).
- Must be built in in kernel !
- Basic structure:
├── bin ├── dev ├── etc ├── lib ├── lib64 -> lib ├── mnt │ ├── cdrom │ ├── floppy │ └── funtoo ├── proc ├── sbin ├── sys ├── tmp ├── usr │ ├── bin │ └── sbin └── var
- Creation (mkdir and cd into it first) :
# mkdir -p bin sbin lib usr/bin usr/sbin usr/lib etc var sys proc sys dev etc mnt/floppy mnt/cdrom mnt/funtoo # chmod -R 755 * # chmod 1777 tmp # ln -s lib64 lib
- Emerge busybox in this subtree and remove unwanted files (eg. /usr/share/doc, and such). Ok because we ask for a static build (this stuff can be built with ulibc also... see also buildroot)
# CFLAGS="-O2 -pipe -mcpu=v9" USE="static make-symlinks" emerge --nodeps --root=/path/to/ramdisk/tree busybox
- Recompile a Linux kernel and put the modules in the cramfs directory structure (make modules_install INSTALL_MOD_PATH=/path/to/ramdisk/tree)
- Don't forget to put a default argument init=... (if is is suitable to keet the init deployed by busybox as is)
- Put something useful in the cutomized init (can be a script) like
#!/bin/ash echo "Hello world"
- Build the cramfs, name it root.img and put it in /usr/src
- Build the tftpboot image => cd /usr/src/linux && make tftpboot.img
- Put the image on a tftpserver
