Ext3 users - Jun 2009 - how to calculate correct values for resize2fs

Hello everybody,

I want to make a new 16 MB partition on the end of my /dev/sda SSD.
Currently the SSD is partitioned in one ext2 /dev/sda1.

My question is how can i make this new partition with the CLI tools. I
tried several things but they keep failing because I don't know how to
calculate with blocks , sectors and MB. Would somebody willing to learn
me some things and maybe show some examples.

I also have some parted question on how to just make a partition from
the free space on the end of the disk.

Thanks in advance,

Best regards,

Jelle

current situation ext2 /dev/sda1, wanted situation ext2 /dev/sda1 and
16MB 0xef /dev/sda2 on the end of /dev/sda
16MB
0xef

PS. I know I got some fsck -n /dev/sda1 errors here. Working on that too.

$ dumpe2fs -h /dev/sda1
dumpe2fs 1.41.6 (30-May-2009)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          3e6384e0-dcaf-4c93-972f-f54c00a7dd22
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      filetype sparse_super
Default mount options:    (none)
Filesystem state:         not clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              492032
Block count:              983973
Reserved block count:     49198
Free blocks:              119386
Free inodes:              355584
First block:              0
Block size:               4096
Fragment size:            4096
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         15872
Inode blocks per group:   496
Last mount time:          Tue Jun 23 10:52:00 2009
Last write time:          Tue Jun 23 10:52:11 2009
Mount count:              9
Maximum mount count:      30
Last checked:             Tue Jun 23 00:23:53 2009
Check interval:           0 (<none>)
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               128

$ sfdisk -d /dev/sda
# partition table of /dev/sda
unit: sectors

/dev/sda1 : start=       63, size=  7871787, Id=83, bootable
/dev/sda2 : start=        0, size=        0, Id= 0
/dev/sda3 : start=        0, size=        0, Id= 0
/dev/sda4 : start=        0, size=        0, Id= 0

$ fdisk -l /dev/sda

Disk /dev/sda: 4034 MB, 4034838528 bytes
255 heads, 63 sectors/track, 490 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xfb38fb38

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1         490     3935893+  83  Linux


bc <<< "16*1024"
16384
bc <<< "3935893 - 16384"
3919509
echo "3935893 - 16384" | bc
3919509

resize2fs /dev/sda1 3919509

bc <<< "4034-16"
resize2fs /dev/sda1 4018M

# result: partition is only 983973 (4K) blocks
# requested: 1028608 blocks
# will not fit exiting

# how can I convert the free space to a partition with parted?
sudo /sbin/parted --script /dev/sda \
mkpart primary 3919509 100% \
print

On Tue, June 23, 2009 02:12, Jelle de Jong wrote:
> I want to make a new 16 MB partition on the end of my /dev/sda SSD.
> Currently the SSD is partitioned in one ext2 /dev/sda1.
> My question is how can i make this new partition with the CLI tools.
Creating partitions is done with {c,s}fdisk. I think cfdisk ask where to 
create this partition (at the end/at the beginning of the disk).
 
> I also have some parted question on how to just make a partition from
> the free space on the end of the disk.
"man parted", but I guess if cfdisk can do it, parted should be able
to do
so as well. Hm, I just checked:

(parted) help mkpart                                                      
  mkpart PART-TYPE [FS-TYPE] START END     make a partition

So, you can actually specify where you want the partition to start.

After creating a new partition, you can mkfs this new one. I did not 
understand at which point you want to "resize" a partition. Resizing a
filesystem is usually done on existing, resized partitions.

C.
-- 
BOFH excuse #51:

Cosmic ray particles crashed through the hard disk platter

Hello Jelle

1. Please don't CC to poster if you answer, we are all on this list and
   get the messages anyways.

2. And please don't full-quote if not *really* necessary.

3. From your other mail:
   > The problem is I have to automate this process
   That's an important information you forgot to mention in the initial
   post ;)

* Jelle de Jong <jelledejong at powercraft.nl> hat geschrieben:
> $ fdisk -l /dev/sda
> Disk /dev/sda: 4034 MB, 4034838528 bytes
> bc <<< "4034-16"
> resize2fs /dev/sda1 4018M
> 
> # result: partition is only 983973 (4K) blocks
> # requested: 1028608 blocks
> # will not fit exiting
4034838528 is 3847 MB and not 4034 like fdisk told you. Obviously fdisk is 
using that bogus SI-numbering.

4018*1024^2 is 1028608 clusters and the underlaying block device of the 
file system only supports 983973 clusters (which it already provides).

So: Take the bytes value, devide it by 1024^2 to gain the real number of
MBs and subtract 18 (not 16) MB in the first call to resize2fs like this:

resize2fs -p /dev/sda1 $(echo "
	scale=0;
	$(
		export LANG=C
		fdisk -l /dev/sda | grep sda: | awk '{ print $5 }'
	)/1024^2-18
" | bc)

Then shrink the partition by 16 MB then resize2fs /dev/sda1 without
argument again to fill up the unused space again.

Remember my advice from the previous mail I'v written as well.

Regards, Bodo