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umount /dev/mapper/nvmeVg-home
umount: /home: target is busy

I looked at this answer and found this useful page I was unable to solve my problem before posting here.

My /var directory is full. /var is on a lvm. Last night, I went to increase the size of /var and accidentally executed lvextend -L+50G /dev/mapper/nvmeVg-home when I should have lvextend -L +50G dev/mapper/nvmeVg-var oops.

So no big deal right? lvextend -L-50G /dev/mapper/nvmeVg-home results in

Size may not be negative.  Invalid argument for --size: -50G.  Error during parsing of command line:

So then I see to shrink a non root volume I must umount the device first. Sure no problem: /umount /dev/mapper/nvmeVg-home results in

umount: /home: target is busy 

So I lsof /dev/mapper/nvmeVg-home and get lots of output. So if I am unable to umount because /home has files in use, then I tried lsof | grep /dev/mapper/nvme returned nothing. I was expecting to see the total number of files open. Then I tried /lsof +f -- /dev/mapper/nvmeVg-home which returned alot of files currently in use. Fine. I then notice /home is mounted to multiple volume groups?(still uncertain on terminology). That's odd. Doesn't look right. Could this be a second issue with in my issue?

nvme0n1         259:0    0 953.9G  0 disk 
├─nvme0n1p1     259:1    0   953M  0 part 
├─nvme0n1p2     259:2    0  46.6G  0 part 
│ └─nvmeVg-var  253:2    0    50G  0 lvm  /var
├─nvme0n1p3     259:3    0  46.6G  0 part 
│ ├─nvmeVg-var  253:2    0    50G  0 lvm  /var
│ ├─nvmeVg-home 253:3    0   150G  0 lvm  /home
│ └─nvmeVg-root 253:4    0   100G  0 lvm  
├─nvme0n1p4     259:4    0  46.6G  0 part 
│ └─nvmeVg-home 253:3    0   150G  0 lvm  /home
├─nvme0n1p5     259:5    0  46.6G  0 part 
│ └─nvmeVg-home 253:3    0   150G  0 lvm  /home
├─nvme0n1p6     259:6    0  46.6G  0 part 
│ └─nvmeVg-root 253:4    0   100G  0 lvm  
├─nvme0n1p7     259:7    0  46.6G  0 part 
│ └─nvmeVg-root 253:4    0   100G  0 lvm  
├─nvme0n1p8     259:8    0  46.6G  0 part 
│ └─nvmeVg-home 253:3    0   150G  0 lvm  /home
├─nvme0n1p9     259:9    0  46.6G  0 part 
├─nvme0n1p10    259:10   0  46.6G  0 part 
├─nvme0n1p11    259:11   0  46.6G  0 part 
└─nvme0n1p12    259:12   0     1G  0 part 

I feel like it is wise to pause and reach out for help at this point.

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    lvextend can only increase the size. This has nothing to do with being mounted. Try lvreduce or lvresize instead, but be very careful not to reduce too much. The lsof command, without options, doesn't print the device on which a file is located, therefore your grepping for nvme returns nothing. /home is not mounted multiple times, but is spread over multiple physical volumes. In short, you have no issue, just a slight misunderstanding how things work. Feb 15, 2021 at 19:03
  • 1
    One way of avoiding damage by reducing the volume too much is by adding the -r option. It also resizes the filesystem. If /home is XFS, however, the command might refuse working, since XFS can't be reduced. Feb 15, 2021 at 19:12

1 Answer 1

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Most probably you are logged in to the system as a regular user. When a regular user logs on, they occupy the /home as part of the path to their home directory.

You must login as root in order to unmount /home. The root user account has a home directory of /root therefore is not affected by /home. Also make sure that no other regular user is logged before you attempt to unmount /home

Then use lvresize command:

lvresize -r -L -50G /dev/mapper/nvmeVg-home

Explanation:

lvresize command will do four things:

  1. Unmount the partition /dev/mapper/nvmeVg-home
  2. Deduct 50GB of disk space from LV which will be credited back into VG (-L -50G)
  3. Check the file system by calling resizefs (-r)
  4. Then remounts the partition /dev/mapper/nvmeVg-home
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  • 2
    Unfortunately, unmounting doesn't solve OP's problem. lvextend still doesn't accept negative sizes. Feb 15, 2021 at 19:08
  • 1
    You must use lvresize command Feb 15, 2021 at 19:11
  • 1
    Correct, and mounting is not the issue here. Feb 15, 2021 at 19:15
  • 1
    I have updated the answer Feb 15, 2021 at 19:15
  • I am logged in as root. Nice! This worked! YAS! Thank you so much! Feb 15, 2021 at 19:52

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