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#1 2007-01-27 11:23:34

qn1234
Member
Registered: 2006-08-18
Posts: 94

pivot_root from USB Memory Stick

I noticed beattie's modification section in the initscripts-0.1/rc.sh file.  Looks like it tries to execute the .DSM-G600-USB-KEY-init file if exists on a USB memory stick labelled DSMG600_KEY.

It would be nice if it looks for the existence of a directory to be used as the pivot_root.  Something like:

mkdir /usbmnt && mount -L DSMG600_KEY /usbmnt
if [ -d /usbmnt/DSMG600_ROOT ]; then
    cd /usbmnt/DSMG600_ROOT
    /sbin/pivot_root . <oldroot>
    ...
fi

At this time, the initrd is already loaded into memory, we need to free it up using:
   fd = open("/dev/ram0", O_RDWR);
   ioctl(fd, BLKFLSZBUF);
   close(fd);

--
Quang

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#2 2007-01-27 19:23:13

beattie
Member / Developer
From: West Coast, USA
Registered: 2006-11-17
Posts: 92
Website

Re: pivot_root from USB Memory Stick

qn1234 wrote:

I noticed beattie's modification section in the initscripts-0.1/rc.sh file.  Looks like it tries to execute the .DSM-G600-USB-KEY-init file if exists on a USB memory stick labelled DSMG600_KEY.

It would be nice if it looks for the existence of a directory to be used as the pivot_root.  Something like:

mkdir /usbmnt && mount -L DSMG600_KEY /usbmnt
if [ -d /usbmnt/DSMG600_ROOT ]; then
    cd /usbmnt/DSMG600_ROOT
    /sbin/pivot_root . <oldroot>
    ...
fi

Could you explain how this is an improvement?.

qn1234 wrote:

At this time, the initrd is already loaded into memory, we need to free it up using:
   fd = open("/dev/ram0", O_RDWR);
   ioctl(fd, BLKFLSZBUF);
   close(fd);

--
Quang

I'll look into this.

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#3 2007-01-28 03:33:54

qn1234
Member
Registered: 2006-08-18
Posts: 94

Re: pivot_root from USB Memory Stick

beattie wrote:

Could you explain how this is an improvement?

This allows you to use your own ramdisk freeing up the original one.

--
Quang

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#4 2007-01-28 08:58:48

beattie
Member / Developer
From: West Coast, USA
Registered: 2006-11-17
Posts: 92
Website

Re: pivot_root from USB Memory Stick

qn1234 wrote:

beattie wrote:

Could you explain how this is an improvement?

This allows you to use your own ramdisk freeing up the original one.

--
Quang

I guess, unless there is a reason otherwise I'd suggest that you what you need to do in /mnt/pivot_root/.DSM-G600-USB-KEY-init, which is what I did.  I don't want to place any restrictions on what can be done in that file. For Instance here is one version of .DSM-G600-USB-KEY-init. that I tested:

Code:

#! /bin/sh

cd /mnt/pivot_root
umount /sys/crfs
losetup -d /dev/loop0
umount /proc
pivot_root /mnt/pivot_root /mnt/pivot_root
exec chroot / /bin/ash
echo $0

Last edited by beattie (2007-01-28 09:10:43)

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#5 2007-01-28 09:22:04

qn1234
Member
Registered: 2006-08-18
Posts: 94

Re: pivot_root from USB Memory Stick

What you have right now would work just fine. 

By the way, you probably fixed it - I noticed you have a command misspelled in the rc.sh file.  It's supposed to be "unmount".

--
Quang

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#6 2007-01-29 00:25:24

beattie
Member / Developer
From: West Coast, USA
Registered: 2006-11-17
Posts: 92
Website

Re: pivot_root from USB Memory Stick

qn1234 wrote:

What you have right now would work just fine. 

By the way, you probably fixed it - I noticed you have a command misspelled in the rc.sh file.  It's supposed to be "unmount".

--
Quang

Are you saying I have a command named "unmount" in my script? or the command "umount" is misspelled?

There is no command "unmount", the correct command is "umount" this spelling goes back to early Unix versions.

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#7 2007-01-29 00:41:42

sala
Member / Site Admin
From: Estonia
Registered: 2006-07-28
Posts: 731
Website

Re: pivot_root from USB Memory Stick

Relax guys big_smile
There was "uount /sys/cfs" or something like that.
And about Dlink, they like to use "ehco" commands and empty if and do statements big_smile


DSM-G600 - NetBSD hdd-boot - 80GB Samsung SP0802N
NSA-220 - Gentoo armv5tel 20110121 hdd-boot - 2x 2TB WD WD20EADS

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#8 2007-01-29 04:34:29

qn1234
Member
Registered: 2006-08-18
Posts: 94

Re: pivot_root from USB Memory Stick

sala wrote:

Relax guys big_smile
There was "uount /sys/cfs" or something like that.
And about Dlink, they like to use "ehco" commands and empty if and do statements big_smile

Yeah, I meant to say I saw "uount /sys/cfs".  Sometimes being up too late at night you got to misspell something. smile

--
Quang

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