Partitions on LINUX

Joy Stick · 07-31-2017, 02:32 PM

Hi all,

I have added some disks

sdb, sdc, sdd, sde

>> Before Partition

PHP Code:



# cat /proc/partitions   
major minor  #blocks  name   
   
   8     0   78643200 sda   
   8     1     104391 sda1   
   8     2   25599577 sda2   
   8     3   10241437 sda3   
   8     4          1 sda4   
   8     5    2867571 sda5   
   8     6    1534176 sda6   
   8     7   38290896 sda7   
   8    16   10485760 sdb   
   8    32   10485760 sdc   
   8    48   10485760 sdd   
   8    64   10485760 sde

>> After partition

PHP Code:



$  cat /proc/partitions   
major minor  #blocks  name   
   
   8     0   78643200 sda   
   8     1     104391 sda1   
   8     2   25599577 sda2   
   8     3   10241437 sda3   
   8     4          1 sda4   
   8     5    2867571 sda5   
   8     6    1534176 sda6   
   8     7   38290896 sda7   
   8    16   10485760 sdb   
   8    17   10482381 sdb1   
   8    32   10485760 sdc   
   8    33   10482381 sdc1   
   8    48   10485760 sdd   
   8    49   10482381 sdd1   
   8    64   10485760 sde   
   8    65   10482381 sde1

marjor and minor, iam NOT getting exactly.

1) Why major values are always 8 ?
2) Why minor values are changing ? especially 16+ ? i.e (16, 32, 48, 64)

3) Why OS displays 2 names for a single disk after partition ?

sdb sdb1,
sdc,sdc1,
sdd,sdd1,
sde,sde1

example :

8 16 10485760 sdb
8 17 10482381 sdb1

TB0ne · 07-31-2017, 02:51 PM

Quote:

Originally Posted by Joy Stick

Hi all,
I have added some disks sdb, sdc, sdd, sde
>> Before Partition

PHP Code:



# cat /proc/partitions   
major minor  #blocks  name   
   
   8     0   78643200 sda   
   8     1     104391 sda1   
   8     2   25599577 sda2   
   8     3   10241437 sda3   
   8     4          1 sda4   
   8     5    2867571 sda5   
   8     6    1534176 sda6   
   8     7   38290896 sda7   
   8    16   10485760 sdb   
   8    32   10485760 sdc   
   8    48   10485760 sdd   
   8    64   10485760 sde

>> After partition

PHP Code:



$  cat /proc/partitions   
major minor  #blocks  name   
   
   8     0   78643200 sda   
   8     1     104391 sda1   
   8     2   25599577 sda2   
   8     3   10241437 sda3   
   8     4          1 sda4   
   8     5    2867571 sda5   
   8     6    1534176 sda6   
   8     7   38290896 sda7   
   8    16   10485760 sdb   
   8    17   10482381 sdb1   
   8    32   10485760 sdc   
   8    33   10482381 sdc1   
   8    48   10485760 sdd   
   8    49   10482381 sdd1   
   8    64   10485760 sde   
   8    65   10482381 sde1

marjor and minor, iam NOT getting exactly.
1) Why major values are always 8 ?
2) Why minor values are changing ? especially 16+ ? i.e (16, 32, 48, 64)

One of the first hits in Google for "what are major and minor numbers in linux" is:
http://www.tldp.org/HOWTO/Partition-...OWTO/x183.html

...which tells you what the 8 is for the major number. You can also look in /usr/src/linux/Documentation/devices.txt and find explanations for both, and this has been covered here before too. http://www.linuxquestions.org/questi...itions-677811/

Quote:

3) Why OS displays 2 names for a single disk after partition ?
sdb sdb1,
sdc,sdc1,
sdd,sdd1,
sde,sde1

example :

8 16 10485760 sdb
8 17 10482381 sdb1

Very obviously, sdb is the entire disk. sdb1 is the first partition on that disk. Very basic partitioning info, as you were asking about previously:
http://www.linuxquestions.org/questi...es-4175607240/

sundialsvcs · 07-31-2017, 03:03 PM

Also, may I take this opportunity to strongly suggest that you learn about "LVM = Logical Volume Management" in Linux. This will make disk management much, much easier.

LVM introduces the concept of a distinction between logical volumes ("the picture seen by the operating system"), and physical volumes ("the actual disks and partitions"). It severs the once-fundamental idea that the two were the same.

For example, a single "logical volume" (mount point ...) can be served by more-than-one "physical volume or portion thereof." You can change this mapping without even having to reboot the system. If you "run out of space somewhere" (normally a very tricky situation to walk away from ...), now it's no big deal: "just add some more, and keep right on going."

Joy Stick · 07-31-2017, 03:17 PM

Actually i added 4 raw devices , then partitioned.
Type of file shows --> b - does it mean block devices ?

PHP Code:



ls -l /dev/sdb*
brw-r----- 1 root disk 8, 16 Jul 31 03:10 /dev/sdb
brw-r----- 1 root disk 8, 17 Jul 31 03:17 /dev/sdb1
 
You have new mail in /var/spool/mail/root
 
[root@CATALOG linux_ora10gsoft]# ls -l /dev/sdc*
brw-r----- 1 root disk 8, 32 Jul 31 03:12 /dev/sdc
brw-r----- 1 root disk 8, 33 Jul 31 03:17 /dev/sdc1
 
[root@CATALOG linux_ora10gsoft]# ls -l /dev/sdd*
brw-r----- 1 root disk 8, 48 Jul 31 03:14 /dev/sdd
brw-r----- 1 root disk 8, 49 Jul 31 03:17 /dev/sdd1
 
[root@CATALOG linux_ora10gsoft]# ls -l /dev/sde*
brw-r----- 1 root disk 8, 64 Jul 31 03:16 /dev/sde
brw-r----- 1 root disk 8, 65 Jul 31 03:17 /dev/sde1

1) After partition why raw devices became as block devices ?
2) Why we need to bind these partitions with the raw devices ?

e.g

PHP Code:



# raw /dev/raw/raw1  /dev/sdb1
# raw /dev/raw/raw2  /dev/sdc1
# raw /dev/raw/raw3  /dev/sdd1
# raw /dev/raw/raw4  /dev/sde1