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Re: [vox-tech] Partition Questions Part 2
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Re: [vox-tech] Partition Questions Part 2

  • Subject: Re: [vox-tech] Partition Questions Part 2
  • From: Mark Kim <mkkim@ucdMAPSavis.edu>
  • Date: Thu, 07 Dec 2000 02:49:18 -0800
  • References: 3A2F3286.3C46D3D1@ucdavis.edu

On Wed, 6 Dec 2000, Robert G. Scofield wrote:

> It appears that Disk Druid works in terms of megabytes, and that Fdisk
> works in terms of blocks.  I can think in terms of megabytes, but
> I can't think in terms of blocks.  What is a block?  What is the ratio
> between megabytes and blocks; that is, how many bytes are in a block or
> how many blocks are in a megabyte?

You can tell fdisk to use megabytes.  When specifying how much to reserve
the disk space, type "+###M" (without the quotes), where ### is some
number in megabytes.

> I'm not sure about this, but I read something like LILO has to be
> installed below the 1204th cylinder.  What is a cylinder?

Get a vinyl record and look for "rings" on it (the circular
grooves).  There are these ring-equivalent things on hard drives called
"cylinders".  They're called "cylinders" instead of "rings" because a hard
drive has several disks inside, and if you find the same "level" of ring
on each disk then it forms a cylinder shape... or that's how I think of

> Fdisk has entries like this:  Start 149    End 620.  Do these numbers
> refer to cylinders?

Apparently.  The last "End" entry matches the total number of cylinders on
my system.

> If not, how do you know if you're below 1204 (or
> whatever the number is)?

Use the "p" command.  It tells you, on the top, how many cylinders the
disk has.  If it's less than 1024, then give it a big sigh of relief.  If
it's not, then try to make sure the root is somewhere above where it looks
like it'll fit under 1024.

My /dev/hda has 1247 cylinders, according to fdisk:

   Command (m for help): p

   Disk /dev/hda: 255 heads, 63 sectors, 1247 cylinders
   Units = cylinders of 16065 * 512 bytes

      Device Boot    Start       End    Blocks   Id  System
   /dev/hda1             1       261   2096451    6  FAT16
   /dev/hda2           262       268     56227+  81  Minix / old Linux
   /dev/hda3   *       269       399   1052257+  83  Linux
   /dev/hda4           400      1247   6811560    5  Extended
   /dev/hda5           400       432    265041   82  Linux swap
   /dev/hda6           433      1247   6546456   83  Linux

So... I have my root partition (/dev/hda3) below the 1024 limit because
the later parts of my disk is much larger.  Also /dev/hda3 ends at 399th

> How do you know which numbers to start from and which numbers to end at
> when you are creating partitions on Fdisk?

Start with 1 increase sequentially.  Doing it any other way may confuse
the system.  Did I ever tell you about how Linux's fdisk and MS's fdisk
got into confusion and how I accidentally deleted partitions I wanted to
keep but survived through using quick wit and cunning?

You can only have 4 primary partitions (/dev/hda1 through /dev/hda4).  You
can have extended partitions (/dev/hda5 through /dev/hda16) if you
sacrifice one primary partition (see above -- my /dev/hda4 has been
sacrificed so I can have /dev/hda5 and /dev/hda6).  The reason for this
rule is because initially Microsoft made an oversight that people
probably wouldn't want more than 4 partitions... then they changed their
minds and decided to add extended partitions, which we now make use of
under the Linux world for happily goodness.


Mark K. Kim
PGP key available upon request.

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