[gentoo-user] Re: USB crucial file recovery

[Kai Krakow]

Am Wed, 31 Aug 2016 02:32:24 +0200
schrieb Alan McKinnon <alan.mckinnon@×××××.com>:

> On 31/08/2016 02:08, Grant wrote:
>  [...]
>  [...]
> >>
> >> You can't control ownership and permissions of existing files with
> >> mount options on a Linux filesystem. See man mount.
> >
> >
> > So in order to use a USB stick between multiple Gentoo systems with
> > ext2, I need to make sure my users have matching UIDs/GIDs?
>
> Yes
>
> The uids/gids/modes in the inodes themselves are the owners and perms,
> you cannot override them.
>
> So unless you have mode=666, you will need matching UIDs/GIDs (which
> is a royal massive pain in the butt to bring about without NIS or
> similar
>
> >  I think
> > this is how I ended up on NTFS in the first place.
>
> Didn't we have this discussion about a year ago? Sounds familiar now
>
> >  Is there a
> > filesystem that will make that unnecessary and exhibit better
> > reliability than NTFS?
>
> Yes, FAT. It works and works well.
> Or exFAT which is Microsoft's solution to the problem of very large
> files on FAT.
>
> Which NTFS system are you using?
>
> ntfs kernel module? It's quite dodgy and unsafe with writes
> ntfs-ng on fuse? I find that one quite solid
>
>
> ntfs-ng does have an annoyance that has bitten me more than once. When
> ntfs-nf writes to an FS, it can get marked dirty. Somehow, when used
> in a Windows machine the driver there has issues with the FS. Remount
> it in Linux again and all is good.

Well, ntfs-ng simply sets the dirty flag which to Windows means "needs
chkdsk". So Windows complains upon mount that it needs to chkdsk the
drive first. That's all. Nothing bad.

> The cynic in me says that Microsoft didn'y implement their own FS spec
> properly whereas ntfs-ng did :-)

Or ntfs-ng simply doesn't trust itself enough while MS trusts itself
too much. Modern Windows kernels almost never set the dirty bit and
instead trust self-healing capabilities of NTFS by using repair
hotspots. By current design, NTFS may be broken at any time while
Windows tells you nothing about it. If the kernel comes across a
defective structure it marks it as a repair hotspot. A background
process repairs these online. If that fails, it is marked for offline
repair which is repaired silently during mount phase. But the dirty
bit? I haven't seen this in a long time (last time was Windows 2003).
Run a chkdsk on an aging Windows installation which has crashed one
or another time. Did you ever see a chkdsk running? No? Then run a
forced chkdsk. Chances are that it will find and repair problems. Run a
non-forced chkdsk: It will only check if there are repair hotspots. If
none are there, it says: Everything fine. It's lying at you.

But still, the papers about NTFS self-healing are quite interesting to
read. It just appears not as mature to me as MS thinks it to be.

-- 
Regards,
Kai

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