James G. Sack (jim) wrote:
Ralph Shumaker wrote:
..
I made my first attempt to follow this outline from the fc7 install dvd,
then from the knoppixV5.1.1 dvd, then finally from the fc4 install dvd.
At the shell prompt # lvm # this gets you an lvm prompt
This did nothing in the fc7 install dvd except give me a new command
prompt (dead end for that path)...
Did nothing?? Not even "..command not found"?
Weird!
Nope. The command is there. Actually, it is a link to something else,
lvm.scan or somesuch (presently no easy way to check). But even
directly launching the one the link points to does nothing except give a
new command line. It's almost as if the program exits so fast that you
miss it even if you *don't* blink.
.. Through knoppix and fc4, this gave me
the lvm> prompt.
lvm> vgscan # scan volume groups to see what's
there
lvm> vgdisplay /dev/VolGroup00/Slash # look in detail at the
logical volume
This gives:
Invalid volume group name: VolGroup00/Slash
Yes there was a typo in the instructions. It may help to see little
classification of the perplexing lvm command repertoire.
The lvm system involves 3 classes of storage "things"
PV: _Physical Volumes_ are the real disk storage resources consigned to
management by the logical volume manager
VG: _Volume Vroups_ are the pools of storage built from PVs and from
which pieces of storage (LVs) are dealt out
LV: _Logical Volumes_ are the end-product that the logical volume
manager delivers to the system for building a filesystem on.
Given that, then commands with a vg prefix, like
vgXXX
tell/do something about/with volume groups
(and similarly for pvXXX and lvXXX)
I would also point out that the vgdisplay and lvdisplay commands may
spit out more information than one wants, sometimes. But there is a more
compact format that you may wish to use for the benefit of discovering
names or sizes.
Try
pvs
vgs
lvs
lvm> help
helps a lot. Even if I didn't already know any of this, the help gives
a couple of screenfulls of a list of commands. And each command gives
at least an idea of what it does, even though a few are not clear if
they are what you want or not.
A further general observation that may help understand the names, is
that volume group names are simply subdirectories of /dev.
Thus
ls -l /dev/VolGroup00
might give (for example)
... Slash -> /dev/mapper/VolGroup00-Slash
... Home -> /dev/mapper/VolGroup00-Home
...
The logical volume names are in turn the entries in the volume group
directory. It's a confusing detail that LV names are symlinks to devices
located under the /dev/mapper directory. Can't do anything about that, I
suppose. The /dev/mapper/XXX thingies are the "devices" used by the system.
</classification-mumbling>
Now, there was probably something else overlooked in Carl's instructions.
When I boot Knoppix in order to poke around with my hard drive, I have
to run not only
vgscan
but
vgchange -ay
to "activate" the VG, before lvm will create its subdirectories in /dev.
This is an example of one of the commands given by "help" that are *not*
clearly the one you want. I tried a couple of others, but not this
one. Thanks.
Thus lvm knows which and where.., but the dev-dir-links-stuff doesn't
exist until VGs are activated.
Then you can do the e2fsck, etc
..<snip>
Hope this helps.
Regards,
..jim
Very helpful. Thanks jim. I'll try the tip.
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