Why can't I create a physical volume?

Question

I was wondering why I can't create a physical volume? Every settings are default for lvm just installed ( For cat /etc/lvm/lvm.conf see https://paste.ubuntu.com/p/QqrszWR8M9/).

Is it because of "Failed to start lvm2.service: Unit lvm2.service is masked"? Thanks.

$ sudo parted -l
Model: ATA TOSHIBA MQ01ABF0 (scsi)
Disk /dev/sda: 500GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End    Size   File system  Name                  Flags
 1      1049kB  538MB  537MB  fat32        EFI System Partition  boot, esp
 2      538MB   500GB  500GB  ext4
$ sudo lvmdiskscan
  /dev/sda1 [     512.00 MiB] 
  /dev/sda2 [    <465.26 GiB] 
  0 disks
  2 partitions
  0 LVM physical volume whole disks
  0 LVM physical volumes

$ sudo pvcreate /dev/sda
  Device /dev/sda excluded by a filter.

$ sudo lvmdiskscan
  /dev/sda1 [     512.00 MiB] 
  /dev/sda2 [    <465.26 GiB] 
  0 disks
  2 partitions
  0 LVM physical volume whole disks
  0 LVM physical volumes


$ sudo pvcreate /dev/sda2
  Can't open /dev/sda2 exclusively.  Mounted filesystem?

I do not. Why default configurations do that? – Tim Feb 22 '19 at 23:46 — Tim, Feb 22 '19 at 23:46

score 1 · Accepted Answer · answered Feb 22 '19 at 23:51

1

You're trying to use the entire /dev/sda for a PV. But you've got (at least) two partitions on that disk (sda1 and sda2), so LVM is rightly refusing to honour your request.

answered Feb 22 '19 at 23:51

Chris Davies

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Thanks. sudo pvcreate /dev/sda2 doesn't work either – Tim Feb 22 '19 at 23:57
It's got a filesystem on it. LVM is doing its best to stop you breaking your system. – Chris Davies Feb 22 '19 at 23:57
Must a physical volume be created from a partition without filesystem? – Tim Feb 22 '19 at 23:58
Yes. Absolutely. – Chris Davies Feb 22 '19 at 23:59
Where is that mentioned in documentation? – Tim Feb 22 '19 at 23:59
First couple of paragraphs for man pvcreate. – Chris Davies Feb 23 '19 at 00:01
Thanks. /dev/sda2 is a single partition, containing / and /home, and I want to separate them into different logical volumes. What shall I do, if I can't mark /dev/sda2 as a physical volume? – Tim Feb 23 '19 at 00:06
Borrow or otherwise obtain an extra disk. Backup your data, and reinstall. – Chris Davies Feb 23 '19 at 00:10
Thanks. WIth what others have told me, I am still confused https://unix.stackexchange.com/questions/502437/how-shall-i-create-a-physical-volume-from-a-partition-containing – Tim Feb 23 '19 at 00:53

Why can't I create a physical volume?

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