[lug] help: creating partitions

[Robert Racansky]

operating system = CentOS 7.4.1708 (Core) in VirtualBox


I want to create a 3 GB partition, /dev/sdb3

This is the video I’m using to learn this :  “Understanding Linux
Logical Volumes”  at  https://www.youtube.com/watch?v=Eu1WrVjzRy8 .

The first time I did this exercise, there was no issue.

But the second time I did it, it required a reboot after “write table
to disk”, after which I continued and finished with no problem.

I’m running into the same “the kernel still uses the old table”
message the third time : * see the very end of this e-mail for the
whole message *.

I’m sure a reboot will work again.  And I’m looking up “partprobe” and
“kpartx” right now, but


QUESTION:  is this normal, since I did not have to reboot the first
time?  And is there a way to avoid this?  Or am I going to have to run
“partprobe” or “kpartx” or reboot every time I do this?

Thanks.



Setup is as below (note that I am omitting some the output for sake of
simplicity and formatting and saving myself some typing):


# df -h

FILESYSTEM = /dev/mapper/centos-root SIZE = 9.2G USED = 1.5G AVAIL = 7.7G


# cat /proc/partitions

8 00 08,388,608 sda [ 8 GB ]
8 01 01,048,576 sda1 [ 1 GB partition ]
8 02 07,339,008 sda2 [ 7 GB partition ]
8 16 20,971,520 sdb [ 20 GB ]
8 17 00,976,896 sdb1 [ 1 GB partition , 1st time I did this exercise ]
8 18 02,097,152 sdb2 [ 2 GB partition , 2nd time I did this exercise ]



# parted /dev/sda print

Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sda: 8,590MB
Partition Table: msdos

1 1,075 MB primary xfs boot
2 7,515 MB primary ___ lvm

Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdb: 21.5GB
Partition Table: msdos

1 1,000 MB primary ___ lvm
2 2,147 MB primary ___ lvm



# lvs

LV = root VG = centos 9.12g
LV = swap VG = centos 820m



# vgs

VG = centos #PV = 3 #LV = 2 VSize = 9.92 GB



# pvs

PV = /dev/sda2 VG = centos FMT = lvm2 PSize = < 7.00 g
PV = /dev/sdb1 VG = centos FMT = lvm2 PSize = 952 m
PV = /dev/sdb2 VG = centos FMT = lvm2 PSize = < 2.00 g


# fdisk /dev/sdb

Command (m for help): n [ add a new partition ]

Partition Type:
p primary (2 primary, 0 extended, 2 free)
e extended
Select (default p): p

Partition number (3,4, default 3): 3

First sector (default 6150144): [ default ]

Last sector, +sectors or +size{K,M,G]: +3G [ for a 3 GB partition ]
Partition 3 of type Linux and of size 3 GiB is set

Command (m for help): t [ change a partition’s system id ]

Partition number (1-3, default 3): 3

Hex code: 8e [ Linux LVM ]
Changed type of partition ‘Linux” to ‘Linux LVM’

Command (m for help): w [ write table to disk and exit ]
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARING: Re-reading this partition table failed with error 16: Device
or resource busy.
The kernel still uses the old table.  The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8).
Syncing disks.

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