* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-20 2:32 ` Johnny Hung
@ 2010-01-20 7:12 ` Matthias Kaehlcke
2010-01-20 7:15 ` Ricard Wanderlof
2010-01-20 7:57 ` Marco Stornelli
2 siblings, 0 replies; 20+ messages in thread
From: Matthias Kaehlcke @ 2010-01-20 7:12 UTC (permalink / raw)
To: Johnny Hung
Cc: Ricard Wanderlof, kernelnewbies, linux-mtd@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-embedded@vger.kernel.org
El Wed, Jan 20, 2010 at 10:32:15AM +0800 Johnny Hung ha dit:
> 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
> > El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
> >
> >> On Tue, 19 Jan 2010, Johnny Hung wrote:
> >>
> >>> Okay, I think the steps is below if my rootfs is ramdisk and configure
> >>> files in jffs2,
> >>>
> >>> 1. cp /etc/* /mnt/mtd/etc/ (/mnt/mtd is my jffs2 fs)
> >>> 2. rm -rf /etc/*
> >>> 3. make symbolic links from all /etc/xx to /mnt/mtd/etc/xxx
> >>> 4. remake ramdisk rootfs
> >>>
> >>> It seems all files in ramdisk rootfs /etc all links to /mnt/mtd/etc/
> >>> and try to modify these files is effective after reboot.
> >>> But is this a common way in embedded linux ?
> >>
>
> Thanks, I understand.
>
> >> In principle, but it is easier (and cleaner) to make a symbolic link from
> >> (say) /etc -> /mnt/mtd/etc without linking every individual file and
> >> directory.
> >
> > i totally agree with ricard when you want to move the entire directory
> > to jffs2 and not only some selected files
> >
> >> You could also use a jffs2 file system in flash for your rootfs, that way
> >> you wouldn't need a ramdisk at all.
> >
> > i'd also recommend you to consider if you really need the
> > ramdisk. when using a ram disk its entire content is loaded to the RAM
> > occupying space, even if you don't use certain files (or part of
> > them). other filesystems are more efficient in this aspect.
> > if the main purpose is to have a read only rootfs, i'd suggest a look
> > at squashfs.
>
> I consider to use ramdisk as rootfs because worry about wrong
> operation in rootfs (is use jffs2 rootfs) and it will cause system
> boot up failed.
you could set up a rootfs partition with a read-only file system
(squashfs, jffs2 mounted ro) and a second partition that's writable.
> Another query, does the syslogd/klogd log files also store in jffs2
> rootfs? Write to jffs2 frequently will reduce flash life cycle.
by default the log files will be written to /var/log, if this
directory happens to be on a jffs2 partition writes will go there and
produce wear out. to avoid this you could set up a small tmpfs (in
RAM) and mount it on /var
--
Matthias Kaehlcke
Embedded Linux Developer
Barcelona
We can't solve problems by using the same kind
of thinking we used when we created them
(Albert Einstein)
.''`.
using free software / Debian GNU/Linux | http://debian.org : :' :
`. `'`
gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `-
^ permalink raw reply [flat|nested] 20+ messages in thread* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-20 2:32 ` Johnny Hung
2010-01-20 7:12 ` Matthias Kaehlcke
@ 2010-01-20 7:15 ` Ricard Wanderlof
2010-01-20 7:17 ` Matthias Kaehlcke
2010-01-22 3:01 ` Johnny Hung
2010-01-20 7:57 ` Marco Stornelli
2 siblings, 2 replies; 20+ messages in thread
From: Ricard Wanderlof @ 2010-01-20 7:15 UTC (permalink / raw)
To: Johnny Hung
Cc: Ricard Wanderlöf, linux-embedded@vger.kernel.org,
kernelnewbies, linux-mtd@lists.infradead.org, Matthias Kaehlcke,
linuxppc-dev@lists.ozlabs.org
On Wed, 20 Jan 2010, Johnny Hung wrote:
>> i'd also recommend you to consider if you really need the
>> ramdisk. when using a ram disk its entire content is loaded to the RAM
>> occupying space, even if you don't use certain files (or part of
>> them). other filesystems are more efficient in this aspect.
>> if the main purpose is to have a read only rootfs, i'd suggest a look
>> at squashfs.
>
> I consider to use ramdisk as rootfs because worry about wrong
> operation in rootfs (is use jffs2 rootfs) and it will cause system
> boot up failed.
You have a point, however, you could do two things to help:
a) Mount the root file system as read-only. That way you can never write
to it, unless you remount it read-write. But you can still reflash that
partition if you need to upgrade.
b) Register the mtd partition holding the root file system as read-only.
This is even more seecure as remounting the file system won't permit
writes. However, it also means you can't write to it for upgrading. (I
don't think the mtd core permits changing an already registered mtd
partition from readonly to writable, but I could be wrong.)
> Another query, does the syslogd/klogd log files also store in jffs2
> rootfs? Write to jffs2 frequently will reduce flash life cycle.
I think it is fairly common to have a combination of devices:
/ (root) is a readonly flash device (mtd partition)
/etc is a writable flash device (mtd partition)
/tmp and /var are ramdisks (tmpfs), so they are writable, but lost when
power is cycled.
/Ricard
--
Ricard Wolf Wanderlöf ricardw(at)axis.com
Axis Communications AB, Lund, Sweden www.axis.com
Phone +46 46 272 2016 Fax +46 46 13 61 30
^ permalink raw reply [flat|nested] 20+ messages in thread* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-20 7:15 ` Ricard Wanderlof
@ 2010-01-20 7:17 ` Matthias Kaehlcke
2010-01-22 3:01 ` Johnny Hung
1 sibling, 0 replies; 20+ messages in thread
From: Matthias Kaehlcke @ 2010-01-20 7:17 UTC (permalink / raw)
To: Ricard Wanderlof
Cc: Johnny Hung, kernelnewbies, linux-mtd@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-embedded@vger.kernel.org
El Wed, Jan 20, 2010 at 08:15:01AM +0100 Ricard Wanderlof ha dit:
> On Wed, 20 Jan 2010, Johnny Hung wrote:
>
>>> i'd also recommend you to consider if you really need the
>>> ramdisk. when using a ram disk its entire content is loaded to the RAM
>>> occupying space, even if you don't use certain files (or part of
>>> them). other filesystems are more efficient in this aspect.
>>> if the main purpose is to have a read only rootfs, i'd suggest a look
>>> at squashfs.
>>
>> I consider to use ramdisk as rootfs because worry about wrong
>> operation in rootfs (is use jffs2 rootfs) and it will cause system
>> boot up failed.
>
> You have a point, however, you could do two things to help:
>
> a) Mount the root file system as read-only. That way you can never write
> to it, unless you remount it read-write. But you can still reflash that
> partition if you need to upgrade.
>
> b) Register the mtd partition holding the root file system as read-only.
> This is even more seecure as remounting the file system won't permit
> writes. However, it also means you can't write to it for upgrading. (I
> don't think the mtd core permits changing an already registered mtd
> partition from readonly to writable, but I could be wrong.)
AFAIK the mtd core doesn't permit changing a partition from ro to
rw. but if you happen to need to reflash the partition anyway, you can
load a tiny kernel modules that changes the flag indicating if a
partition is writable.
i once had to recurr to this solution and it works ;)
--
Matthias Kaehlcke
Embedded Linux Developer
Barcelona
Tant qu'il y aura sur terre des hommes pour qui existe un concept
d' 'honneur national', la menace d'une nouvelle guerre subsistera
(B. Traven)
.''`.
using free software / Debian GNU/Linux | http://debian.org : :' :
`. `'`
gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `-
^ permalink raw reply [flat|nested] 20+ messages in thread* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-20 7:15 ` Ricard Wanderlof
2010-01-20 7:17 ` Matthias Kaehlcke
@ 2010-01-22 3:01 ` Johnny Hung
1 sibling, 0 replies; 20+ messages in thread
From: Johnny Hung @ 2010-01-22 3:01 UTC (permalink / raw)
To: Ricard Wanderlof
Cc: Matthias Kaehlcke, kernelnewbies, linux-mtd@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-embedded@vger.kernel.org
2010/1/20 Ricard Wanderlof <ricard.wanderlof@axis.com>:
>
> On Wed, 20 Jan 2010, Johnny Hung wrote:
>
>>> i'd also recommend you to consider if you really need the
>>> ramdisk. when using a ram disk its entire content is loaded to the RAM
>>> occupying space, even if you don't use certain files (or part of
>>> them). other filesystems are more efficient in this aspect.
>>> if the main purpose is to have a read only rootfs, i'd suggest a look
>>> at squashfs.
>>
>> I consider to use ramdisk as rootfs because worry about wrong
>> operation in rootfs (is use jffs2 rootfs) and it will cause system
>> boot up failed.
>
> You have a point, however, you could do two things to help:
>
> a) Mount the root file system as read-only. That way you can never write to
> it, unless you remount it read-write. But you can still reflash that
> partition if you need to upgrade.
>
> b) Register the mtd partition holding the root file system as read-only.
> This is even more seecure as remounting the file system won't permit writes.
> However, it also means you can't write to it for upgrading. (I
> don't think the mtd core permits changing an already registered mtd
> partition from readonly to writable, but I could be wrong.)
>
>> Another query, does the syslogd/klogd log files also store in jffs2
>> rootfs? Write to jffs2 frequently will reduce flash life cycle.
>
> I think it is fairly common to have a combination of devices:
>
> / (root) is a readonly flash device (mtd partition)
> /etc is a writable flash device (mtd partition)
> /tmp and /var are ramdisks (tmpfs), so they are writable, but lost when
> power is cycled.
I think it's a good combination for my board. How do I sepcific the
/etc to another mtd part?
The busybox init will parse /etc/inittab after setup signal handler
and initializes console. I only
know to do it is to re-mount etc directory from another mtd to /etc.
Is it right?
Thank your help.
BRs, H. Johnny
>
> /Ricard
> --
> Ricard Wolf Wanderlöf ricardw(at)axis.com
> Axis Communications AB, Lund, Sweden www.axis.com
> Phone +46 46 272 2016 Fax +46 46 13 61 30
>
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-20 2:32 ` Johnny Hung
2010-01-20 7:12 ` Matthias Kaehlcke
2010-01-20 7:15 ` Ricard Wanderlof
@ 2010-01-20 7:57 ` Marco Stornelli
2010-01-20 10:21 ` Matthias Kaehlcke
2010-01-22 3:07 ` Johnny Hung
2 siblings, 2 replies; 20+ messages in thread
From: Marco Stornelli @ 2010-01-20 7:57 UTC (permalink / raw)
To: Johnny Hung
Cc: Matthias Kaehlcke, Ricard Wanderlof, kernelnewbies,
linux-mtd@lists.infradead.org, linuxppc-dev@lists.ozlabs.org,
linux-embedded@vger.kernel.org
2010/1/20 Johnny Hung <johnny.hacking@gmail.com>:
> 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
>> El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
>>
> I consider to use ramdisk as rootfs because worry about wrong
> operation in rootfs (is use jffs2 rootfs) and it will cause system
> boot up failed.
> Another query, does the syslogd/klogd log files also store in jffs2
> rootfs? Write to jffs2 frequently will reduce flash life cycle.
>
> BRs, H. Johnny
>>
>> --
In general a good splitting for rootfs could be: squashfs for rootfs,
tmpfs for volatile data (/tmp), ubifs (with a flash partition) for
"strong" permanent data (/etc, ....) and pramfs for "light" permanent
data (/var/log, .....).
I think you should "split" your rootfs. Ramdisk is an old approach
with some drawbacks.
Marco
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-20 7:57 ` Marco Stornelli
@ 2010-01-20 10:21 ` Matthias Kaehlcke
2010-01-20 11:54 ` Marco Stornelli
2010-01-22 3:07 ` Johnny Hung
1 sibling, 1 reply; 20+ messages in thread
From: Matthias Kaehlcke @ 2010-01-20 10:21 UTC (permalink / raw)
To: Marco Stornelli
Cc: Johnny Hung, Ricard Wanderlof, kernelnewbies,
linux-mtd@lists.infradead.org, linuxppc-dev@lists.ozlabs.org,
linux-embedded@vger.kernel.org
El Wed, Jan 20, 2010 at 08:57:44AM +0100 Marco Stornelli ha dit:
> 2010/1/20 Johnny Hung <johnny.hacking@gmail.com>:
> > 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
> >> El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
> >>
> > I consider to use ramdisk as rootfs because worry about wrong
> > operation in rootfs (is use jffs2 rootfs) and it will cause system
> > boot up failed.
> > Another query, does the syslogd/klogd log files also store in jffs2
> > rootfs? Write to jffs2 frequently will reduce flash life cycle.
> >
> > BRs, H. Johnny
> >>
> >> --
>
> In general a good splitting for rootfs could be: squashfs for rootfs,
> tmpfs for volatile data (/tmp), ubifs (with a flash partition) for
> "strong" permanent data (/etc, ....) and pramfs for "light" permanent
> data (/var/log, .....).
if ubifs is a good choice depends on the size of the partition, iirc
it has a significant overhead for very small partitions.
once using ubi it could be interesting to set up the read-only rootfs
partition upon ubi in order to spread the wear out over a maximum of blocks.
--
Matthias Kaehlcke
Embedded Linux Developer
Barcelona
You can chain me, you can torture me, you can even
destroy this body, but you will never imprison my mind
(Mahatma Gandhi)
.''`.
using free software / Debian GNU/Linux | http://debian.org : :' :
`. `'`
gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `-
^ permalink raw reply [flat|nested] 20+ messages in thread* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-20 10:21 ` Matthias Kaehlcke
@ 2010-01-20 11:54 ` Marco Stornelli
0 siblings, 0 replies; 20+ messages in thread
From: Marco Stornelli @ 2010-01-20 11:54 UTC (permalink / raw)
To: Matthias Kaehlcke
Cc: Johnny Hung, Ricard Wanderlof, kernelnewbies,
linux-mtd@lists.infradead.org, linuxppc-dev@lists.ozlabs.org,
linux-embedded@vger.kernel.org
2010/1/20 Matthias Kaehlcke <matthias@kaehlcke.net>:
> El Wed, Jan 20, 2010 at 08:57:44AM +0100 Marco Stornelli ha dit:
>
>> 2010/1/20 Johnny Hung <johnny.hacking@gmail.com>:
>> > 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
>> >> El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
>> >>
>> > I consider to use ramdisk as rootfs because worry about wrong
>> > operation in rootfs (is use jffs2 rootfs) and it will cause system
>> > boot up failed.
>> > Another query, does the syslogd/klogd log files also store in jffs2
>> > rootfs? Write to jffs2 frequently will reduce flash life cycle.
>> >
>> > BRs, H. Johnny
>> >>
>> >> --
>>
>> In general a good splitting for rootfs could be: squashfs for rootfs,
>> tmpfs for volatile data (/tmp), ubifs (with a flash partition) for
>> "strong" permanent data (/etc, ....) and pramfs for "light" permanent
>> data (/var/log, .....).
>
> if ubifs is a good choice depends on the size of the partition, iirc
> it has a significant overhead for very small partitions.
>
> once using ubi it could be interesting to set up the read-only rootfs
> partition upon ubi in order to spread the wear out over a maximum of blocks.
>
I don't know the size constraints of Johnny, so it can be useful to use jffs2.
Marco
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-20 7:57 ` Marco Stornelli
2010-01-20 10:21 ` Matthias Kaehlcke
@ 2010-01-22 3:07 ` Johnny Hung
2010-01-22 8:14 ` Marco Stornelli
1 sibling, 1 reply; 20+ messages in thread
From: Johnny Hung @ 2010-01-22 3:07 UTC (permalink / raw)
To: Marco Stornelli
Cc: Matthias Kaehlcke, Ricard Wanderlof, kernelnewbies,
linux-mtd@lists.infradead.org, linuxppc-dev@lists.ozlabs.org,
linux-embedded@vger.kernel.org
2010/1/20 Marco Stornelli <marco.stornelli@gmail.com>:
> 2010/1/20 Johnny Hung <johnny.hacking@gmail.com>:
>> 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
>>> El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
>>>
>> I consider to use ramdisk as rootfs because worry about wrong
>> operation in rootfs (is use jffs2 rootfs) and it will cause system
>> boot up failed.
>> Another query, does the syslogd/klogd log files also store in jffs2
>> rootfs? Write to jffs2 frequently will reduce flash life cycle.
>>
>> BRs, H. Johnny
>>>
>>> --
>
It seems there are a lot of file-systems I have to study :P. The same
question is
how to split my rootfs? Re-mount /etc, /var to another file-sysyem mtd part when
system boot up?
Thank your good advice.
BRs, H. Johnny
> In general a good splitting for rootfs could be: squashfs for rootfs,
> tmpfs for volatile data (/tmp), ubifs (with a flash partition) for
> "strong" permanent data (/etc, ....) and pramfs for "light" permanent
> data (/var/log, .....).
> I think you should "split" your rootfs. Ramdisk is an old approach
> with some drawbacks.
>
> Marco
>
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-22 3:07 ` Johnny Hung
@ 2010-01-22 8:14 ` Marco Stornelli
2010-01-25 4:09 ` Johnny Hung
0 siblings, 1 reply; 20+ messages in thread
From: Marco Stornelli @ 2010-01-22 8:14 UTC (permalink / raw)
To: Johnny Hung
Cc: Matthias Kaehlcke, Ricard Wanderlof, kernelnewbies,
linux-mtd@lists.infradead.org, linuxppc-dev@lists.ozlabs.org,
linux-embedded@vger.kernel.org
2010/1/22 Johnny Hung <johnny.hacking@gmail.com>:
> 2010/1/20 Marco Stornelli <marco.stornelli@gmail.com>:
>> 2010/1/20 Johnny Hung <johnny.hacking@gmail.com>:
>>> 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
>>>> El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
>>>>
>>> I consider to use ramdisk as rootfs because worry about wrong
>>> operation in rootfs (is use jffs2 rootfs) and it will cause system
>>> boot up failed.
>>> Another query, does the syslogd/klogd log files also store in jffs2
>>> rootfs? Write to jffs2 frequently will reduce flash life cycle.
>>>
>>> BRs, H. Johnny
>>>>
>>>> --
>>
>
> It seems there are a lot of file-systems I have to study :P. The same
> question is
> how to split my rootfs? Re-mount /etc, /var to another file-sysyem mtd part when
> system boot up?
>
Simply, you can mount each mount point with the fstab file and a
script, same approach of every linux distribution, nothing more. Even
in the pc world you can mount your /home on a partition with ext3,
/var in a partition with ext4, and so on. A very simple approach to
setup the system, it is to start with NFS for example with "whole" fs,
copy what you need in the right place, setup the start-up script and
reboot.
Marco
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-22 8:14 ` Marco Stornelli
@ 2010-01-25 4:09 ` Johnny Hung
2010-01-25 8:27 ` Chris Simmonds
0 siblings, 1 reply; 20+ messages in thread
From: Johnny Hung @ 2010-01-25 4:09 UTC (permalink / raw)
To: Marco Stornelli
Cc: Matthias Kaehlcke, Ricard Wanderlof, kernelnewbies,
linux-mtd@lists.infradead.org, linuxppc-dev@lists.ozlabs.org,
linux-embedded@vger.kernel.org
2010/1/22 Marco Stornelli <marco.stornelli@gmail.com>:
> 2010/1/22 Johnny Hung <johnny.hacking@gmail.com>:
>> 2010/1/20 Marco Stornelli <marco.stornelli@gmail.com>:
>>> 2010/1/20 Johnny Hung <johnny.hacking@gmail.com>:
>>>> 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
>>>>> El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
>>>>>
>>>> I consider to use ramdisk as rootfs because worry about wrong
>>>> operation in rootfs (is use jffs2 rootfs) and it will cause system
>>>> boot up failed.
>>>> Another query, does the syslogd/klogd log files also store in jffs2
>>>> rootfs? Write to jffs2 frequently will reduce flash life cycle.
>>>>
>>>> BRs, H. Johnny
>>>>>
>>>>> --
>>>
>>
>> It seems there are a lot of file-systems I have to study :P. The same
>> question is
>> how to split my rootfs? Re-mount /etc, /var to another file-sysyem mtd part when
>> system boot up?
>>
>
Yes, I know. So if I want set etc directoyr to /dev/mtd5 not in rootfs
/, I need to add "/dev/mtdblock5 /etc jffs2 defaults
0 0" in /etc/fstab file but rootfs doesn't contain /etc
directory because /etc directoyr is store in /dev/mtdblock5.
Do you know what I mean? The kernel execute /sbin/init after mount
rootfs and /sbin/init is link to busybox, busybox will read
/etc/inittab file to initial. The problem is coming, how busybox to
read /etc in rootfs before mount /dev/mtdblock5 to /etc? There is no
program to mount /dev/mtdblock5 to /etc before busybox init execute.
I think I must mistake some concept, please give me a hint.
Thank you
BRs, H. Johnny
> Simply, you can mount each mount point with the fstab file and a
> script, same approach of every linux distribution, nothing more. Even
> in the pc world you can mount your /home on a partition with ext3,
> /var in a partition with ext4, and so on. A very simple approach to
> setup the system, it is to start with NFS for example with "whole" fs,
> copy what you need in the right place, setup the start-up script and
> reboot.
>
> Marco
>
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-25 4:09 ` Johnny Hung
@ 2010-01-25 8:27 ` Chris Simmonds
2010-01-25 8:43 ` Johnny Hung
0 siblings, 1 reply; 20+ messages in thread
From: Chris Simmonds @ 2010-01-25 8:27 UTC (permalink / raw)
To: Johnny Hung
Cc: Marco Stornelli, Matthias Kaehlcke, Ricard Wanderlof,
kernelnewbies, linux-mtd@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-embedded@vger.kernel.org
Johnny Hung wrote:
> 2010/1/22 Marco Stornelli <marco.stornelli@gmail.com>:
>> 2010/1/22 Johnny Hung <johnny.hacking@gmail.com>:
>>> 2010/1/20 Marco Stornelli <marco.stornelli@gmail.com>:
>>>> 2010/1/20 Johnny Hung <johnny.hacking@gmail.com>:
>>>>> 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
>>>>>> El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
>>>>>>
>>>>> I consider to use ramdisk as rootfs because worry about wrong
>>>>> operation in rootfs (is use jffs2 rootfs) and it will cause system
>>>>> boot up failed.
>>>>> Another query, does the syslogd/klogd log files also store in jffs2
>>>>> rootfs? Write to jffs2 frequently will reduce flash life cycle.
>>>>>
>>>>> BRs, H. Johnny
>>>>>> --
>>> It seems there are a lot of file-systems I have to study :P. The same
>>> question is
>>> how to split my rootfs? Re-mount /etc, /var to another file-sysyem mtd part when
>>> system boot up?
>>>
> Yes, I know. So if I want set etc directoyr to /dev/mtd5 not in rootfs
> /, I need to add "/dev/mtdblock5 /etc jffs2 defaults
> 0 0" in /etc/fstab file but rootfs doesn't contain /etc
> directory because /etc directoyr is store in /dev/mtdblock5.
> Do you know what I mean? The kernel execute /sbin/init after mount
> rootfs and /sbin/init is link to busybox, busybox will read
> /etc/inittab file to initial. The problem is coming, how busybox to
> read /etc in rootfs before mount /dev/mtdblock5 to /etc? There is no
> program to mount /dev/mtdblock5 to /etc before busybox init execute.
>
> I think I must mistake some concept, please give me a hint.
> Thank you
> BRs, H. Johnny
>
You have two /etc directories: one in the the read-only root file system
and one in the jffs2 fs. In the root fs you have /etc/fstab,
/etc/inittab and any scripts it may call. The init program will mount
/dev/mtdblock5 over the top of the /etc that is in the rootfs, so giving
you the read/write version of /etc. Any files open in the old /etc -
e.g. /etc/inittab - will continue to be open, but any new files opened
in /etc will use the read/write version in jffs2. You can also do some
interesting things with symbolic links... This technique works. I have
used it in several projects.
--
Chris Simmonds 2net Limited
chris@2net.co.uk http://www.2net.co.uk/
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.
2010-01-25 8:27 ` Chris Simmonds
@ 2010-01-25 8:43 ` Johnny Hung
0 siblings, 0 replies; 20+ messages in thread
From: Johnny Hung @ 2010-01-25 8:43 UTC (permalink / raw)
To: chris
Cc: Marco Stornelli, Matthias Kaehlcke, Ricard Wanderlof,
kernelnewbies, linux-mtd@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-embedded@vger.kernel.org
2010/1/25 Chris Simmonds <chris@2net.co.uk>:
> Johnny Hung wrote:
>>
>> 2010/1/22 Marco Stornelli <marco.stornelli@gmail.com>:
>>>
>>> 2010/1/22 Johnny Hung <johnny.hacking@gmail.com>:
>>>>
>>>> 2010/1/20 Marco Stornelli <marco.stornelli@gmail.com>:
>>>>>
>>>>> 2010/1/20 Johnny Hung <johnny.hacking@gmail.com>:
>>>>>>
>>>>>> 2010/1/19 Matthias Kaehlcke <matthias@kaehlcke.net>:
>>>>>>>
>>>>>>> El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:
>>>>>>>
>>>>>> I consider to use ramdisk as rootfs because worry about wrong
>>>>>> operation in rootfs (is use jffs2 rootfs) and it will cause system
>>>>>> boot up failed.
>>>>>> Another query, does the syslogd/klogd log files also store in jffs2
>>>>>> rootfs? Write to jffs2 frequently will reduce flash life cycle.
>>>>>>
>>>>>> BRs, H. Johnny
>>>>>>>
>>>>>>> --
>>>>
>>>> It seems there are a lot of file-systems I have to study :P. The same
>>>> question is
>>>> how to split my rootfs? Re-mount /etc, /var to another file-sysyem mtd
>>>> part when
>>>> system boot up?
>>>>
>> Yes, I know. So if I want set etc directoyr to /dev/mtd5 not in rootfs
>> /, I need to add "/dev/mtdblock5 /etc jffs2 defaults
>> 0 0" in /etc/fstab file but rootfs doesn't contain /etc
>> directory because /etc directoyr is store in /dev/mtdblock5.
>> Do you know what I mean? The kernel execute /sbin/init after mount
>> rootfs and /sbin/init is link to busybox, busybox will read
>> /etc/inittab file to initial. The problem is coming, how busybox to
>> read /etc in rootfs before mount /dev/mtdblock5 to /etc? There is no
>> program to mount /dev/mtdblock5 to /etc before busybox init execute.
>>
>> I think I must mistake some concept, please give me a hint.
>> Thank you
>> BRs, H. Johnny
>>
>
I got it. The rootfs contains at least /etc directory, /etc/inittab,
/etc/fstab. Bysybox will read /etc/fstab to mount etc to rootfs's etc
from other partition. Okay, it's reasonable. Another query, how to do
it in many Linux dist as Macro mentioned, use initramfs ? I am sure I
can arrange / to /dev/hda1 and /etc to /dev/hda2.
Thank you so much
BRs, H. Johnny
> You have two /etc directories: one in the the read-only root file system and
> one in the jffs2 fs. In the root fs you have /etc/fstab, /etc/inittab and
> any scripts it may call. The init program will mount /dev/mtdblock5 over the
> top of the /etc that is in the rootfs, so giving you the read/write version
> of /etc. Any files open in the old /etc - e.g. /etc/inittab - will continue
> to be open, but any new files opened in /etc will use the read/write version
> in jffs2. You can also do some interesting things with symbolic links...
> This technique works. I have used it in several projects.
>
> --
> Chris Simmonds 2net Limited
> chris@2net.co.uk http://www.2net.co.uk/
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-embedded" in
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>
^ permalink raw reply [flat|nested] 20+ messages in thread