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noatime on boot disk

Posted on 2001-07-12
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Last Modified: 2012-08-13
I'm developing an embedded system with a flash disk on module root partition mounted in read-only.

Linux keeps on updateing the access time also if it is on a read-only partition. Mounting the partition with the noatime flag solve this problem, but I don't know how to force it at boot time to avoid any kind of remounting once the system is up.

Thank you in advance.
Livio
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Question by:livio
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6 Comments
 
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Expert Comment

by:ahoffmann
ID: 6280905
add the  noauto  option to the corresponding mount point in /etc/fstab
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Author Comment

by:livio
ID: 6281799
The root partition is mounted by the kernel with its own parameters and not with the /etc/fstab options.

I can modify those parameters with rdev, but I do not know how to force the noatime flag.

Thank you.
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by:ahoffmann
ID: 6281812
oops, didn't read carefully
> .. disk on module root partition ..

how do you mount this? could you please post the command.
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by:bryanh
ID: 6282479
I don't get it.  The system is updating atimes (file access times) on a read only filesystem image?  You can't update anything on a read only filesystem image.  What's the filesystem type?  Is this a special filesystem driver for a "flash disk on module root partition" (I had trouble parsing that sentence)?
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Author Comment

by:livio
ID: 6285232
I read on many news on the embedded mailing-lists that the access time keep on to be updated on the ext2 filesystem also if it is mounted in read-only mode.

I'm using the ext2 filesystem to run my emebedded system that has the root partition on a solid state disk made with flash memories ("disk on module"), so I MUST avoid all those unusefull writes.

The "disk on module" is mounted on a normal IDE connector and there is nothing different between it and a normal hard disk from the linux point of view.

I'm using lilo as a boot loader with the read-only option enabled.
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Accepted Solution

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bryanh earned 600 total points
ID: 6288295
Hmm.  It certainly doesn't make any sense that the kernel would update the atime on a read only filesystem image.  And in the source code, update_atime() in fs/inode.c, it quite simply ignores the request if the inode is read-only (which in ext2 is always true when the mount is read-only).  And I just accessed a file on a read-only ext2 filesystem image on my Linux 2.2.19.

So I don't know what you and the people on the mailing lists are experiencing.

The read-only option is settable on the initial root filesystem image only as a special case; you can't set any other mount options, such as NOATIME.

I suppose you could make your initial root filesystem a ramdisk (initrd) and then mount the disk-on-module with the NOATIME option via a startup script.
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