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MacGyver031
Tux's lil' helper
Joined: 11 Jul 2004
Posts: 141
Location: Ilavalai, Sri Lanka
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 Posted: Tue Jan 31, 2012 10:30 am Post subject: [Solved] Gentoo on compactflash card |
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Hi folks,
I have been playing around with gentoo on compactflash. So far I have managed to set up and run Gentoo on squashfs but I have failed in getting the system to run on flashdisk with the known structure (/bin /boot ....).
For those who do not want to read long threads to get to the question:
How can I mount /dev/sda1 readonly and overlay with aufs.ko so that I can mount /dev/sda1 to manually commit changes without using genkernel? I would be happy if I could mount /dev/sda1 to /mnt/sda1 on the "newroot", but I doesn't work (reported error: "/dev/sda1 is already mounted on /mnt/disk", force mounting results in empty /mnt/sda1).
My approach was create initrd.gz (includes busybox and modprobe), mount the flash readonly at /mnt/flash, create a tmpfs on /tmp, and use aufs to overlay /mnt/disk with /tmp to /mnt/root (this is my "newroot") so that changes are faked to write on disk. Then handover to /mnt/root and startup /sbin/init. This works well, but I am unable to mount /dev/sda1 on "newroot"/mnt/sda1 so that I can manually commit changes to /etc.
As I have said, as soon as I would like to mount "newroot"/mnt/sda1, mount denies to do so.
init (softlinked to linuxrc) thus far:
| Code: |
#!/bin/sh
mount none /proc -t proc
mount none /sys -t sysfs
mount /dev/sda1 /mnt/flash -o ro
modprobe aufs
mount none /tmp -t tmpfs
mount none /mnt/root -t aufs -o dirs=/tmp:/mnt/flash
umount /sys
umount /proc
exec switch_root /mnt/root /sbin/init
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_________________
Sincerely your
Joanand K.
MacBook Pro 5.1: 2.4GHz Core2 Duo, 4096MB, 500GB, NVidia 9400/9600 M GT
Gentoo, Kernel 3.4.9, XOrg, Fluxbox.
Last edited by MacGyver031 on Thu Feb 02, 2012 2:43 pm; edited 1 time in total |
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MacGyver031
Tux's lil' helper
Joined: 11 Jul 2004
Posts: 141
Location: Ilavalai, Sri Lanka
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| Posted: Thu Feb 02, 2012 2:42 pm Post subject: [Solved] Gentoo on compactflash card |
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Hi,
After some trial and kernel panics, I got it working:
Basically you have to mount the drive to /mnt/flash in RAM, create /newroot in RAM, bind /mnt/flash/tmp (which lies on the flash) to tmpfs.
Then you overlay with AUFS /mnt/flash and /mnt/flash/tmp to /newroot, then move the mount to /newroot/mnt/sda1 and then switch_root.
Effectively (I have made everything modular, so I had to load necessary modules manually)
| Code: |
#!/bin/sh
## Project: Embedded Gentoo (mini- and micro-servants)
## Date: February 01, 2012
## Author: Joanand Kuharajasekaram
## Copyright: 1995-2012, Mac Industries
##
## Description: Gentoo on Wrap, Alix, Acer, Dell and others with flash and aufs.
clear
echo "Mac Industries Five Thousand"
mount none /proc -t proc -o noexec,nosuid,nodev >/dev/null 2>&1
mount none /sys -t sysfs -o noexec,nosuid,nodev >/dev/null 2>&1
modprobe -q sd_mod
modprobe -q ext2
## Qemu-KVM:
modprobe -q ata_piix
## Wrap:
#modprobe -q pata_sc1200
## Alix:
#modprobe -q pata_cs5536
mount /dev/sda1 /mnt/flash -o ro
modprobe -q aufs
mount none /mnt/flash/tmp -t tmpfs
mkdir -p /newroot
mount none /newroot -t aufs -o dirs=/mnt/flash/tmp:/mnt/flash
mkdir -p /newroot/mnt/sda1
mount --move /mnt/flash /newroot/mnt/sda1
umount /sys
umount /proc
exec switch_root /newroot /sbin/init
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With this, I now have the possibility to remount /mnt/sda1 rw and save changes. I have also seen the approach of Gentoo-LiveCD, which creates links to read-only directories and copies of /etc, /root and /home to the tmpfs /. This approach uses more memory in my application than aufs.
Aufs: Total memory usage 22MB
Tmpfs with copy (ala LiveCD, with squashfs): Total memory usage 80MB
If someone needs help in creating initrd, do not hesistate to ask.
_________________
Sincerely your
Joanand K.
MacBook Pro 5.1: 2.4GHz Core2 Duo, 4096MB, 500GB, NVidia 9400/9600 M GT
Gentoo, Kernel 3.4.9, XOrg, Fluxbox. |
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Installing Gentoo
