I think that's right Russ, thanks. We bother with Read-Only root as a simple
overkill peace-of-mind enhancement (IE none of the OS or App files can be
written without unlocking first). I'm not enough of a Unix Guru to know how to
minimize the footprint of /var, unfortunately.
What I want to know is we are operational for years now with /var writes going
on. So far during this time, we have had the kernel remount /var as read-only
exactly twice. (Kernel does this for problem mounts). Reboot fixed it in both
cases.
Does anyone here know what we can expect when the SD card "fails?" Will it be
all at once, or will things degrade over time? Is there a method to detect it
in advance, say similarly to counting bad sectors on a disk drive?
Oh, and one more question about what you said, Russ. (Thanks!) I've seen some
SD cards set up by others, where small, empty, unmounted partitions are
inserted between the active partitions, but I never knew why. Do you think
that this an attempt to reduce the effect of having two partitions on the same
erase block?!?
THANK YOU
On Jun 22, 2012, at 1:50 PM, Don Tucker wrote:
> Damn it! Well, thanks for the information, Russ.
>
> Don
> On 6/22/2012 3:37 PM, Russell N. Nelson - rnnelson wrote:
>> My research into SD card reliability says that even a read-only root won't
>> help you if you have a different partition mounted read-write on the same
>> SDcard. The wear-leveling system can cause two partitions to be handed the
>> same flash block, so that writing into the read-write partition can cause
>> part of the read-only filesystem to get rewritten and possibly corrupted if
>> the sdcard write fails.
>>
>> There's no magic bullet, I fear.
>> -russ
>> ________________________________________
>> From: on behalf of Clark
>> Dunson
>> Sent: Tuesday, June 19, 2012 12:00 PM
>> To:
>> Subject: Re: [ts-7000] read-only Debian on TS-7260
>>
>> Yes Don, we ship that way. TS-7260/2.6.21 read-only root
>>
>> This wiki is particularly helpful:
>>
>> http://wiki.debian.org/ReadonlyRoot
>>
>> We had to partition the SD card to make room for /var which still must be
>> mounted RW.
>> All attempts to mount the NAND on TS-7260 have failed once booted from SD
>> card have failed though.
>>
>> On Jun 19, 2012, at 8:18 AM, Don Tucker wrote:
>>
>>> That's great. The SD card image that I'm currently using was developed for
>>> the TS-7400, so my procedure can probably follow yours. Did you use the
>>> unionfs method described in the TS document I linked to?
>>>
>>> Don
>>>
>>> On 6/19/2012 10:04 AM, Russell N. Nelson - rnnelson wrote:
>>>> No, but I got it working on a TS-7400.
>>>> ________________________________________
>>>> From: on behalf of Don
>>>> Tucker
>>>> Sent: Tuesday, June 19, 2012 10:50 AM
>>>> To:
>>>> Subject: [ts-7000] read-only Debian on TS-7260
>>>>
>>>> I'm currently running a 2.6.21-ts kernel and Debian file system on an SD
>>>> card with a TS-7260. I'm considering trying to restrict all of the file
>>>> system writes to a single read-write partition, and leave everything
>>>> else read-only. I found this resource on Technologic Systems' website
>>>> that describes setting up a read-only file system for the TS-73XX.
>>>>
>>>> http://www.embeddedarm.com/about/resource.php?item=466
>>>>
>>>> Has anyone tried this for the TS-72XX?
>>>>
>>>> Don
>>>>
>>>>
>>
>>
>> ------------------------------------
>>
>> Yahoo! Groups Links
>>
>>
>>
>>
>
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