Handling power off with no shutdown

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I have a control system that is running Linux.  The user will not be
"shutting down", he will be simply turn the power off.  When this
happens, I see "/dev/hda1 was not cleanly unmounted, check forced" and
then it scans/repairs the drive.

It seems that I could use some combination of initrd, a ramdisk and
remounting the hard drive as read-only to avoid this, but I have no
idea where to start.

Can anyone give me a clue?  (I'm using SUSE v7.0 with RTAI)

-Brian Rosenthal

Re: Handling power off with no shutdown

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In my system i've mounted the whole thing readonly, and only if i have to
write something to the disk (or in my case a cf-card) i have to remount it
in rw-mode, then i write, then i remount it in ro-mode again. All the
temporary stuff which linux will write goes into a ramdisk, so per
example /var is mounted in a ramdisk. In this way you can minimize the
writings.

This is maybe not the best way, but for me it works.

hth, Jens
--
Die o.a. Adresse ist OK, wird aber nicht gelesen. Für Mails an mich bitte
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Re: Handling power off with no shutdown
If nothing is written to the disk it can be mounted as read-only.

If the system writes to the disk at random times the only way is to add
a battery to provide power to do a shut down when power is switched off.

Using a journalling file system reduced the boot time after a not clean
shout down and enables a cleaner remounting of a not cleanly dismounted
partition, but increases the risk of interrupting a write cycles as a
lot more writes are done with a single transaction. So it's not
recommended when using some kind of flash instead of a disk.

-Michael

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