Re: Preupgrade??

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On 05/01/2010 01:08 AM, Marcel Rieux wrote:
> On Fri, Apr 30, 2010 at 8:33 PM, Kevin J. Cummings
> <cummings@xxxxxxxxxxxxxxxxxx <mailto:cummings@xxxxxxxxxxxxxxxxxx>> wrote:

>     Necessary?  no.  But you may have problems upgrading if you don't have
>     enough storage in /boot for whichever upgrade method you choose to use
>     during the upgrade.
> 
> 
> I'm afraid there's a lot of stupid questions you'll have to forgive
> here, but I'm completely lost.
> 
> As I said, I have 290 MB for /boot but, with the 3 past kernels
> installed, I hardly use more that ¼ of it. When a new version of Fedora
> is installed, it installs a new kernel and deletes, as usual, the oldest
> one. Why is much space needed? 

Because preupgrade downloads a bunch of stuff that it uses to bootstrap
the upgraded kernel with, and it puts some of that in /boot/upgrade.
That includes a kernel, a ramdisk image, and a couple of other small
files.  During the first step when it downloads everything, it has not
yet deleted your old kernel(s), so all of this stuff must co-exist in
your /boot.  Sometimes if you run out of space in /boot, preupgrade is
smart enough to download some of these files for you, but you would need
a working network interface during the bootstrap, which may or may not
be problematic.  Suffice to say, that you may or may not have enough
space in boot.  You won't know until you try.

> 
>     Me?  I recently deleted my LVMs and re-partitioned my F13 system with a
>     single / partitition (ext4) and a swap partition (instead of having a
>     /boot partition, now /boot is just a subdirectory of /.
> 
> 
> It seems to me this makes sense, except I'd also have a /home partition.

It should never be a problem having a separate /home partition.  My home
server as separate partitions for:  /, /usr, /home, /local, /var, and
whatever else I decide I want disk space for (which for me is /src,
/mythtv, and /iso).  YMMV

> Say you have a 20GB partition for / on a desktop. Is there really much
> chance that it will one day get filled and that there will be no cruft
> to remove? I mean on a desktop...!

ISTR that the separate /boot partition had its roots way back when grub
needed to be able to find its kernel and ramdisk files within the first
1024 cylinders of your boot disk (stupid BIOS limitation).  This is why
/boot came into existance.  It remains in existance due to grub still
not being able to read those files out of LVMs and because of a lack of
ext4 support (which is only just now getting into grub in F13?).  So, if
you eliminate LVMs, you've gone most of the way towards eliminating the
need for a /boot partition.

> When you can get a 1TB HD for less than $100, is there any sense in
> trying to cut the 20GB to 10 GB and having to use LVM?
> 
> Wikipedia says:
> 
> On small systems (like a desktop at home), instead of having to guess
> how big a partition needs to be, LVM allows you to resize your disk
> partitions easily as needed.

I had an LVM system one day, spread across 2 PVs.  Once of those disks
died, and I lost my entire system.  B^(  When I bought my replacement
drive, I eliminated the LVMs for straight partitions.  I was able to
recover *most* of my system from some old backups (wouldn't ya know I
had stopped doing backups regularly some time before I tried that
upgrade....)

>  http://en.wikipedia.org/wiki/Logical_Volume_Manager_%28Linux%29
> 
> Is LVM the default when you make a Fedora desktop installation? I hope
> not. If it is, I believe I disabled it since, when I go into Logical
> Volume Management, all partitions show: Uninitiated disk entity. Does
> LVM change the way fstab looks?

You can always choose to not use LVM when you install Fedora, but you
have to be comfortable with selecting the advanced disk partitioning and
using the tools provided.  Not everyone is.

>     Swap?  Non-sequitor.  /boot is file-system (disk) space. 
> 
> 
> This goes with what I asked here:
> 
> "When a new version of Fedora is installed, it installs a new kernel and
> deletes, as usual, the oldest one. Why is much space needed? "

The deletion of old kernels doesn't actually happen until *after* the
new system is installed (just in case it fails, you can still re-boot
the old system).  Once the upgrade actually starts to install the
upgraded packages is when things pass a point of no return.  After that
if any drastic happens it becomes a case of recovering the new system.
I've had that happen many times.  Most recently due to a power outage
during installation on a machine without a UPS.  (ouch!)  The machine
could no longer boot either the new nor the old system and had to be
re-installed.  Even though my data was still there, some was borked
during the boot-up, and resulted in a kernel panic.  Not nice.

> I thought maybe, when a new version of Fedora is installed, that some
> compiling operation are needed that occupy a lot of space in the /boot
> partition, and that /swap could be temporarily be used. I'm afraid this
> does not make much sense. The problem is I can't figure out what does.

Not compiling, but downloads.  It needs the filesystem space to store
files in.

>> Now, if you want to trade off some of your swap partition to add to your
> 
>     /boot partition, that *may* be do-able if the are adjacent on the disk,
> 
> 
> They are not. Countrary to what is most commonly suggested, long ago, I
> took the habit to put swap at the end of the disk so that each
> revolution of the HD read/writes more sectors, making swap more
> efficient. /boot is at the beginning of the disk.

Oh, well.  LVM can get around that as it doesn't care where in the PV
the actual data is.

> But, since I believe I don't use LVM, is there any way I can get rid of
> the ext3 boot partition and use a /boot directory in / without doing a
> back-up/restore?

Sure, from your already booted system, unmount /boot.  Now mount it
somewhere else (like /mnt/boot).  Now you can copy the data from
/mnt/boot to /boot in your / partition.  Now you no longer need the
/boot partition (assuming grub can read what it needs out of your /
partition).  You may need to edit your /boot/grub/grub.conf file to add
/boot to some of the paths that exist there (I did) and possibly update
the "active" partition from your old /boot partition to your new /
partition.  You may need to re-install grub if your old /boot and your
new / are on different disks.

> The whole section between equal signs will be qualified by most here as
> an unnecessary rant. Don't feel obliged to read it.
> 
> =================

[rant removed]

> =======================
> 
> I believe there should be a page on FedoraProject to explain how to get
> rid of that ext3 /boot partition. Of course, for most people, I suppose
> it won't be much of an issue for most users but, when a 500 MB boot
> partition is now suggested for /boot -- which 25 times my first HD! --,
> it certainly doesn't look very clean.

Knowledge of this sort is a dangerous weapon.  It is known by those who
understand it and are willing to possibly shoot themselves in the foot
because they know what they are doing.  When you get to that stage, you
will understand.

> Maybe we can try to explain why so much space is needed -- only for LVM,
> or for non-LVM too? -- and see what's the way of getting out of the way
> this relic that will keep newcomers wondering and pondering at each
> upgrade for years to come?

As things are fixed, things change.  As new functionality is added,
things changed.  Not always for the better.

I hope this has been helpful.

-- 
Kevin J. Cummings
kjchome@xxxxxxx
cummings@xxxxxxxxxxxxxxxxxx
cummings@xxxxxxxxxxxxxxxxxxxxxxx
Registered Linux User #1232 (http://counter.li.org)
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