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Re: xfs file system - apparently for real men 8-)

On Wed, 05 Dec 2001, Bret Waldow wrote:
> Thanks for the tips.  Maybe you can help with this newbie question...

Interestingly, just after I posted this I found that Daniel Phillips has
posted some tests done with ReiserFS, comparing it's indexing to his
ext[23] directory indexing.

This showed that the hash _default_ function in ReiserFS performs poorly
when names are randomly distributed rather than sequential. :)

> I have a Thinkpad, dual boot W2k & Linux. I bought a second hard disk,
> identical to the one that came with the laptop, and a carrier for the
> Ultrabay.

Cool. How do those work? I am thinking of replacing my Gateway laptop
with a Thinkpad, now that Gateway have closed down their Asia-Pacific
operation entirely. :(

> My backup is: dd if=/dev/hda of=/dev/hdc
> This works great, but I expect it's copying my (you guessed it)
> reiserfs partitions verbatim.

*nod*  Everything, in fact. :)

> So I imagine if I wanted to reformat with different partition types,
> to restore I'd go in on an hdaX level, like hda5 = hdc5, but I can't
> do a byte for byte copy if I want to end up with a different fs type.

Well, sort of. You can't change the content of the filesystem doing
things like that. So, you want to copy the /content/ rather than the raw

> What command would work, please? I figured I might need to answer this
> question some day, but maybe sooner is better.

The two popular choices for this are tar(1) and cpio(1). :)

Basically, plug in both hard disks and boot from something that you will
not be modifying. I have done this using Debian install disks and
mini-linux distributions as well as by moving root from partition to

Basically, the process is:

* make sure the partition you are changing is unmounted
* make sure all it's data is backed up
* make sure it's unmounted again (because you forgot to backup first,
  right ;)

Now, this is where it starts to get potentially destructive, so be

* mount the duplicate partition and make sure it's got the right data.

Once you have done that, make sure your backups are up to date and:[1]

* mke2fs (or whatever) the partition you are changing to a new type.
* mount it somewhere, possibly in it's correct location

* execute:
] (cd /mnt/old && tar cp .) | (cd /mnt/new && tar xvp)

Verify, by reading the manpage and info for tar, that these are enough
options for you. Do this as *ROOT*, because anything else *will not

* check your level of paranoia
* assuming it's high, do something like (assuming you use bash as your shell):
] cd /mnt/new && find . -type f -print | while read file; do
      cmp "$file" "/mnt/old/$file" ||
      echo -e "\007\007\007\007\007 **** $file is corrupt! help! help!"
  done | tee /tmp/compare.log

This verifies that the files on the old and new partition are
byte-for-byte identical. This probably matters to you, but skip it if
you are sure that you got it right.

Then, unmount the old partition and *KEEP IT FOR A MONTH!!!!!*

Don't delete it. Make sure it's available just in case you forgot
something vital on it. Really.


Oh, there are other tools that might work in place of tar or cpio, too.
rsync(1) works, and there are a number of "directory tree clone"
programs out there that should work too.

Also, something that's a file level backup tool like kbackup should
work, modulo the fact that I have not /tried/ this.

Personally, I just used tar. :)


[1]  Have I labored this point enough yet?

[2]  Unless you want all the files in the target to be owned by that
     user. I do my home directory, on those rare occasions when I do
     move it, as a normal user.

And when they come to ethnically cleanse me, 
Will you speak out? Will you defend me? 
Or laugh through a glass eye as they rape our lives, 
Trampled underfoot by the right on the rise.
        -- Pop Will Eat Itself, _Ich Bin Ein Auslander_ (Dos Dedos Mis Amigos)

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