2009/10/17 michael <michael.copel...@gmail.com>

> PJ wrote:
>
>> michael wrote:
>>
>>
>>> PJ wrote:
>>>
>>>
>>>> Why is it that the manual pages, as thorough as they may be, are very,
>>>> very confusing.
>>>> Perhaps I am being too wary, but I find that too many
>>>> instructions/examples are stumbling blocks to appreciation of the whole
>>>> system:
>>>> for instance, let's look at the instructions for changing disk labels
>>>> with glabel or is it tunefs ?
>>>> man glabel(8):
>>>>
>>>> for UFS the file system label is set with
>>>> tunefs(8)
>>>> <
>>>> http://www.freebsd.org/cgi/man.cgi?query=tunefs&sektion=8&apropos=0&manpath=FreeBSD+7.2-RELEASE
>>>> >.
>>>>
>>>> what happened to glabel?
>>>> man tunefs(8)
>>>> The *tunefs* utility cannot be
>>>> run on an active file system. To change an active file system, it must
>>>> be downgraded to read-only or unmounted.
>>>>
>>>> So, you have to run tunefs from an active file system to modify another
>>>> disk?
>>>> but from man tunefs:
>>>> BUGS
>>>> This utility should work on active file systems.
>>>> What in hades does this mean--just above it says cannot be run on active
>>>> file systems. ???
>>>>  To change the root file
>>>> system, the system must be rebooted after the file system is tuned.
>>>>
>>>> You can tune a file system, but you cannot tune a fish.
>>>> How cute... And fish eat bugs.
>>>>
>>>> Seriously, now to the manual:
>>>> To create a permanent label for a UFS2 file system without destroying
>>>> any data, issue the following command:
>>>> # tunefs -L /home/ /dev/da3
>>>>
>>>> Oh? home is what? What does this have to do with the partitions?
>>>> Here's from man glabel(8):
>>>>
>>>> EXAMPLES
>>>> The following example shows how to set up a label for disk ``da2'', cre-
>>>> ate a file system on it, and mount it:
>>>> glabel label -v usr /dev/da2
>>>> newfs /dev/label/usr
>>>> mount /dev/label/usr /usr
>>>> [...]
>>>> umount /usr
>>>> glabel stop usr
>>>> glabel unload
>>>>
>>>> The next example shows how to set up a label for a UFS file system:
>>>> tunefs -L data /dev/da4s1a
>>>> mount /dev/ufs/data /mnt/data
>>>>
>>>> Am I to understand that glabel is only for a new system? What's with the
>>>> newfs... I'm trying to set labels on an system that is already set up.
>>>> And, the glabel examle above is not for UFS file systems? Oh, that's for
>>>> tunefs?
>>>> So why are we even dealing with this glabel?
>>>>
>>>> from manual:
>>>> # tunefs -L /home/ //dev/da3/
>>>> A label should now exist in /dev/ufs which may be added to /etc/fstab:
>>>> /dev/ufs/home /home ufs rw 2 2
>>>>
>>>> Why? Is this necessary? and somewhere I saw "tunefs -L volume
>>>> /dev/da0s1a" or something like that. Does that mean that each partition
>>>> should be tunefsd? Maybe the guys who programmed this stuff understand;
>>>> I sure don't. I just want to be able to set the labels according to what
>>>> they say can be done... so shy not have a clear and concise explanation?
>>>>
>>>> Do people who write this stuff ever read it? Tell me that its clear and
>>>> simple and to the point... so far, I have been running back and forth
>>>> between half a dozen web pages trying to understand what is going
>>>> on... and doing things through a dense fog does not produce creative
>>>> results!
>>>> _______________________________________________
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>>>>
>>>>
>>> ok, in short since i didn't see anyone answer this directly, your
>>> question of tunefs vs glabel:
>>>
>>> tunefs is for UFS: it labels a UFS filesystem, no matter the device,
>>> ie: ad or da. tunefs is part of the filesystem utilities for UFS.
>>> good example, can't tunefs -L SWAP /dev/ad0s1b if it is a swap. you
>>> can glabel it.
>>>
>>> glabel is for labeling a device itself. you can glabel an ntfs
>>> filesystem or ext2, whatever.
>>>
>>>
>>>
>>>
>> Thanks for that, Michael.
>> But can you explain what this means? It just is not clear for me.
>> "# tu;nefs -L home /dev/da3"
>> This puts a label on that disk? So now it can be referred to as home?
>> da3 = home ?
>>
>> I'll try to delve into the man glabel further... but things still look
>> murky.
>>
>>
>>
> tunefs -L HOME /dev/da3 will put the label /dev/ufs/HOME pointing to
> /dev/da3 . da3=home. exactly correct.
> the main idea behind that is that you can move the device around, etc.
> since fstab is looking in /dev/ufs/NAMES_OF_DISKS/PARTITIONS instead of
> /dev/da[0-9] type setup. you can move it to any controller and still boot(if
> you have the driver for the controller).
>
> the glabel command can label ANY disk/slice/partition. its great when you
> get away form the old mbr setup and switch to gpt. gpt lets you have an
> arbitrary number of partitions. and when you think about it, names are so
> much better than numbers anyway, its why we use DNS on networks. imagine
> having to remember every ip you have to use.
>
> peace
>
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>

"arbitrary number of partitions"

erm 128 IIRC, so practically yes
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