fsid syntax

fsid syntax

[Bernd Schubert]

Hi,

probably on Friday I need to make use of setting the fsid in the /etc/exports.

Since I can't find the syntax in the exports manpage (manpage was last time 
changed on Januar, while the fsid-feature seems to be become added to cvs on 
February).

So I'd like to know the exact sytanx, is for example:

/testdir	testnode(fsid=/dev/sdb)

correct to make 'testnode' believing that sdb is exported?


Thanks in advance,

Bernd

-- 
Bernd Schubert
Physikalisch Chemisches Institut
Abt. Theoretische Chemie
INF 229, 69120 Heidelberg
Tel.: 06221/54-5210
e-mail: 	bernd (dot) schubert (at) pci (dot) uni-heidelberg (dot) de 


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Re: fsid syntax

[Trond Myklebust]

>>>>> " " == Bernd Schubert <bernd-schubert@web.de> writes:

     > Hi, probably on Friday I need to make use of setting the fsid
     > in the /etc/exports.

     > Since I can't find the syntax in the exports manpage (manpage
     > was last time changed on Januar, while the fsid-feature seems
     > to be become added to cvs on February).

     > So I'd like to know the exact sytanx, is for example:

     > /testdir testnode(fsid=/dev/sdb)

The fsid is a number, not a device. In principle you can set it to any
number you like as long as you keep it consistent over reboots.

One suggestion is to use the device major/minor number in the format
minor + (major * 256). (That's what nfsd uses by default for block
devices.)

Cheers,
  Trond


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Re: fsid syntax

[Bernd Schubert]

On Wednesday 07 August 2002 17:26, Trond Myklebust wrote:
> >>>>> " " == Bernd Schubert <bernd-schubert@web.de> writes:
>      > Hi, probably on Friday I need to make use of setting the fsid
>      > in the /etc/exports.
>      >
>      > Since I can't find the syntax in the exports manpage (manpage
>      > was last time changed on Januar, while the fsid-feature seems
>      > to be become added to cvs on February).
>      >
>      > So I'd like to know the exact sytanx, is for example:
>      >
>      > /testdir testnode(fsid=/dev/sdb)
>
> The fsid is a number, not a device. In principle you can set it to any
> number you like as long as you keep it consistent over reboots.
>
> One suggestion is to use the device major/minor number in the format
> minor + (major * 256). (That's what nfsd uses by default for block
> devices.)
>
> Cheers,
>   Trond
>
>

Uh, good that I asked for this, so I was completely wrong.

Is there a way to get the current fsid (after a reboot on Friday the fsid will 
change and I don't want to reboot our clients) ? Or is it simply the fsid of 
e.g.  /dev/sdb, so that I can get it with statfs() ?

Thanks for your help,

Bernd


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Re: fsid syntax

[Bogdan Costescu]

On Wed, 7 Aug 2002, Bernd Schubert wrote:

> Is there a way to get the current fsid (after a reboot on Friday the fsid will 
> change and I don't want to reboot our clients) ?

One of the first lines of the output from "dumpe2fs /dev/sdbx" provided 
that you use ext2/ext3 on that partition.

-- 
Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu@IWR.Uni-Heidelberg.De



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Re: fsid syntax

[Bernd Schubert]

On Wednesday 07 August 2002 17:26, Trond Myklebust wrote:
> >>>>> " " == Bernd Schubert <bernd-schubert@web.de> writes:
>      > Hi, probably on Friday I need to make use of setting the fsid
>      > in the /etc/exports.
>      >
>      > Since I can't find the syntax in the exports manpage (manpage
>      > was last time changed on Januar, while the fsid-feature seems
>      > to be become added to cvs on February).
>      >
>      > So I'd like to know the exact sytanx, is for example:
>      >
>      > /testdir testnode(fsid=/dev/sdb)
>
> The fsid is a number, not a device. In principle you can set it to any
> number you like as long as you keep it consistent over reboots.
>
> One suggestion is to use the device major/minor number in the format
> minor + (major * 256). (That's what nfsd uses by default for block
-------------------------  	   	----------------

Sorry for my last mail, I missed from your mail, that nfs uses minor + (major 
* 256).


sdb6 would be: 16(scsi disk devices) + 6(partition number) + 8*256 = 2070, 
wouldn't it?

Thanks again for your help,

Bernd


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Re: fsid syntax

[Bernd Schubert]

>
> sdb6 would be: 16(scsi disk devices) + 6(partition number) + 8*256 = 2070,
> wouldn't it?

Sorry,

of course I meant:  16(sdb) + 6(partition number) + 8(scsi disk devices)*256


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Re: fsid syntax

[Neil Brown]

On Wednesday August 7, bernd-schubert@web.de wrote:
> On Wednesday 07 August 2002 17:26, Trond Myklebust wrote:
> > The fsid is a number, not a device. In principle you can set it to any
> > number you like as long as you keep it consistent over reboots.
> >
> > One suggestion is to use the device major/minor number in the format
> > minor + (major * 256). (That's what nfsd uses by default for block
> > devices.)
> >
> > Cheers,
> >   Trond
> >
> >
> 
> Uh, good that I asked for this, so I was completely wrong.
> 
> Is there a way to get the current fsid (after a reboot on Friday the fsid will 
> change and I don't want to reboot our clients) ? Or is it simply the fsid of 
> e.g.  /dev/sdb, so that I can get it with statfs() ?
> 
> Thanks for your help,

Sorry, you cannot do that.  The filehandles created with fsid=foo are
different from any filehandle created without fsid=.

If you want to change the device on the server what you need to do is:

1/ well in advance, add an 'fsid=42'(*) export option. 
   Clients using old file handles will still work.  Clients that
   subsequently mount will get new-style file handles.
2/ At your convenience, remount the filesystem on all clients, either
   by umount/mount or reboot or whatever.
3/ When all, or enough, clients have remounted, you can safely change
   the device number without affecting clients.

(*)  I really don't think that basing the fsid on the device number is
at all sensible.  Afterall, that is what we are trying to avoid.
Just pick a number, any number.
1 for the first filesystem, 2 for the second.
Your age for the filesystem storing you home directory.
42 for the filesystem storing the Great Question of Life, The
Universe, and Everything.

NeilBrown


> 
> Bernd
> 
> 
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Re: fsid syntax

[Benjamin LaHaise]

On Thu, Aug 08, 2002 at 06:31:01AM +1000, Neil Brown wrote:
> (*)  I really don't think that basing the fsid on the device number is
> at all sensible.  Afterall, that is what we are trying to avoid.
> Just pick a number, any number.
> 1 for the first filesystem, 2 for the second.
> Your age for the filesystem storing you home directory.
> 42 for the filesystem storing the Great Question of Life, The
> Universe, and Everything.

It would make sense for filesystems that have a GUID, like ext2/3, 
for it to be used as the fsid.  Just a thought.

		-ben


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Re: fsid syntax

[Neil Brown]

On Wednesday August 7, bcrl@redhat.com wrote:
> On Thu, Aug 08, 2002 at 06:31:01AM +1000, Neil Brown wrote:
> > (*)  I really don't think that basing the fsid on the device number is
> > at all sensible.  Afterall, that is what we are trying to avoid.
> > Just pick a number, any number.
> > 1 for the first filesystem, 2 for the second.
> > Your age for the filesystem storing you home directory.
> > 42 for the filesystem storing the Great Question of Life, The
> > Universe, and Everything.
> 
> It would make sense for filesystems that have a GUID, like ext2/3, 
> for it to be used as the fsid.  Just a thought.

Nice thought, but I don't really have enough bits.  32 is about all I
can afford for NFSv2.

If we had a VFS interface that allowed generic access to a GUID, then
an export option that says "use the GUID if present for NFSv3 or
higher" might be OK...

NeilBrown


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Re: fsid syntax

[Bernd Schubert]

> Sorry, you cannot do that.  The filehandles created with fsid=foo are
> different from any filehandle created without fsid=.
>
> If you want to change the device on the server what you need to do is:
>
> 1/ well in advance, add an 'fsid=42'(*) export option.
>    Clients using old file handles will still work.  Clients that
>    subsequently mount will get new-style file handles.
> 2/ At your convenience, remount the filesystem on all clients, either
>    by umount/mount or reboot or whatever.
> 3/ When all, or enough, clients have remounted, you can safely change
>    the device number without affecting clients.
>
> (*)  I really don't think that basing the fsid on the device number is
> at all sensible.  Afterall, that is what we are trying to avoid.
> Just pick a number, any number.
> 1 for the first filesystem, 2 for the second.
> Your age for the filesystem storing you home directory.
> 42 for the filesystem storing the Great Question of Life, The
> Universe, and Everything.
>
> NeilBrown
>

Hello Neil,

thank you for telling me about this. 

Bernd


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Re: fsid syntax

[Frank van Maarseveen]

On Thu, Aug 08, 2002 at 06:31:01AM +1000, Neil Brown wrote:
> 
> (*)  I really don't think that basing the fsid on the device number is
> at all sensible.  Afterall, that is what we are trying to avoid.
> Just pick a number, any number.

The number depends on the goal of specifying an fsid at all. Example:
Say you want to move the disk to a new system without affecting current
mounts. It is possible to use IP numbers for fsids and to set multiple
addresses on a NIC, for every exported filesystem. So when the disk or
partition is moved to a different system, the IP addresses have to move
to the NIC of the other system as well.

Actually I experimented with this some time ago (using a home brew fsid
kind of patch).


-- 
Frank


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