# Reducing the root LV

## Contents

  - [Overview](#overview)
  - [Procedure](#procedure)
      - [Without lvresize -r flag](#without-lvresize--r-flag)
      - [With lvresize -r flag](#with-lvresize--r-flag)


## Overview

Reducing the root logical volume requires booting into a rescue environment that has the LVM utilities.

> Some rescue images have a version of the LVM utilities that were released missing a critical shim needed to resize filesystems using the `-r` flag to `lvresize`. It may or may not be necessary to resize the filesystem as a separate step, both are outlined.


## Procedure

Given this current configuration of a 250G boot volume:

| **Mount** | **Size**  | **VG / LV**      |
| --------- | --------- | ---------------- |
| /boot     | 250M      | n/a              |
| /tmp      | 2G        | vglocal / lvtmp  |
| swap      | 2G        | vglocal / lvswap |
| /         | remainder | vglocal / lvroot |


We'll reduce the root (/) volume and grow swap and /tmp to end up with:

| **Mount** | **Size**  | **VG / LV**      |
| --------- | --------- | ---------------- |
| /boot     | 250M      | n/a              |
| /tmp      | 4G        | vglocal / lvtmp  |
| swap      | 32G       | vglocal / lvswap |
| /         | remainder | vglocal / lvroot |


### Without lvresize -r flag

```
##
## DO NOT MOUNT ANY FILESYSTEMS DURING RESCUE BOOT
##

# activate all LVM
lvm vgchange -a y

# fsck the filesystems; it's normal to get a message about a time error that needs fixed
fsck -fC /dev/vglocal/lvroot
fsck -fC /dev/vglocal/lvtmp

# shrink the ext3/4 root far below what we need
resize2fs -p /dev/vglocal/lvroot 200G

# reduce the root LV a bit above what we just resized (+5GB)
lvm lvresize /dev/vglocal/lvroot --size 205G

# increase swap and tmp LVs
lvm lvresize /dev/vglocal/lvswap --size 32G
lvm lvresize /dev/vglocal/lvtmp --size 4G

# re-grow the root LV back to max space
lvm lvresize -l +100%FREE /dev/vglocal/lvroot

# re-grow the / and /tmp ext3/4 to fill the increased LVs
resize2fs -p /dev/vglocal/lvroot
resize2fs -p /dev/vglocal/lvtmp

# fsck the filesystems again
fsck -fC /dev/vglocal/lvroot
fsck -fC /dev/vglocal/lvtmp

# rescue image 'mkswap' is sometimes not able to see a large swap
reboot

# finally, make a new swap signature that sees the whole LV
swapoff /dev/vglocal/lvswap
mkswap /dev/vglocal/lvswap
swapon /dev/vglocal/lvswap
```

### With lvresize -r flag

```
##
## DO NOT MOUNT ANY FILESYSTEMS DURING RESCUE BOOT
##

# activate all LVM
lvm vgchange -a y

# fsck the filesystems; it's normal to get a message about a time error that needs fixed
fsck -fC /dev/vglocal/lvroot
fsck -fC /dev/vglocal/lvtmp

# reduce the size of LV root a tad more than we need
lvm lvresize -r /dev/vglocal/lvroot --size 200G

# increase swap and tmp LVs
lvm lvresize /dev/vglocal/lvswap --size 32G
lvm lvresize /dev/vglocal/lvtmp --size 4G

# re-grow the root LV back to max space
lvm lvresize -r -l +100%FREE /dev/vglocal/lvroot

# fsck the filesystems again
fsck -fC /dev/vglocal/lvroot
fsck -fC /dev/vglocal/lvtmp

# rescue image 'mkswap' is sometimes not able to see a large swap
reboot

# finally, make a new swap signature that sees the whole LV
swapoff /dev/vglocal/lvswap
mkswap /dev/vglocal/lvswap
swapon /dev/vglocal/lvswap
```