# 逻辑卷缩减的基本概念
# 缩减逻辑卷的大小
# 需要先缩减文件系统
# 危险操作，可能导致数据丢失
# 需要备份数据

# lvreduce命令详解

# 1. 缩减指定大小的逻辑卷
# lvreduce -L -20G /dev/datavg/datalv
WARNING: Reducing active logical volume to 80.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce datavg/datalv? [y/n]: y
Size of logical volume datavg/datalv changed from 100.00 GiB (25600 extents) to 80.00 GiB (20480 extents).
Logical volume datavg/datalv successfully resized.

# 2. 缩减到指定大小的逻辑卷
# lvreduce -L 60G /dev/datavg/datalv
WARNING: Reducing active logical volume to 60.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce datavg/datalv? [y/n]: y
Size of logical volume datavg/datalv changed from 80.00 GiB (20480 extents) to 60.00 GiB (15360 extents).
Logical volume datavg/datalv successfully resized.

# 3. 缩减指定PE数量的逻辑卷
# lvreduce -l -5120 /dev/datavg/datalv
WARNING: Reducing active logical volume to 10240 extents
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce datavg/datalv? [y/n]: y
Size of logical volume datavg/datalv changed from 60.00 GiB (15360 extents) to 40.00 GiB (10240 extents).
Logical volume datavg/datalv successfully resized.

# 4. 强制缩减逻辑卷
# lvreduce -f -L -10G /dev/datavg/datalv
Size of logical volume datavg/datalv changed from 40.00 GiB (10240 extents) to 30.00 GiB (7680 extents).
Logical volume datavg/datalv successfully resized.

# 5. 缩减逻辑卷并显示详细信息
# lvreduce -v -L -5G /dev/datavg/datalv
WARNING: Reducing active logical volume to 25.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce datavg/datalv? [y/n]: y
Finding free space in volume group datavg
Reducing datavg/datalv to 25.00 GiB
Size of logical volume datavg/datalv changed from 30.00 GiB (7680 extents) to 25.00 GiB (6400 extents).
Logical volume datavg/datalv successfully resized

# 6. 查看lvreduce命令的帮助
# lvreduce –help

# 不同文件系统的缩减

# 1. ext4文件系统缩减
# 卸载文件系统
# umount /data

# 检查文件系统
# e2fsck -f /dev/datavg/datalv
e2fsck 1.46.5 (30-Dec-2021)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/datavg/datalv: 11/3276800 files (0.0% non-contiguous), 200000/13107200 blocks

# 缩减ext4文件系统
# resize2fs /dev/datavg/datalv 40G
resize2fs 1.46.5 (30-Dec-2021)
Resizing the filesystem on /dev/datavg/datalv to 10485760 (4k) blocks.
The filesystem on /dev/datavg/datalv is now 10485760 (4k) blocks long.

# 缩减逻辑卷
# lvreduce -L 40G /dev/datavg/datalv
WARNING: Reducing active logical volume to 40.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce datavg/datalv? [y/n]: y
Size of logical volume datavg/datalv changed from 50.00 GiB (12800 extents) to 40.00 GiB (10240 extents).
Logical volume datavg/datalv successfully resized.

# 2. XFS文件系统缩减（不支持在线缩减）
# XFS文件系统不支持缩减
# 需要先备份数据，然后删除逻辑卷，重新创建

# 3. 一键缩减（ext4）
# lvreduce -L 30G -r /dev/datavg/datalv
WARNING: Reducing active and open logical volume to 30.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce datavg/datalv? [y/n]: y
Size of logical volume datavg/datalv changed from 40.00 GiB (10240 extents) to 30.00 GiB (7680 extents).
Logical volume datavg/datalv successfully resized.
resize2fs 1.46.5 (30-Dec-2021)
Resizing the filesystem on /dev/datavg/datalv to 7864320 (4k) blocks.
The filesystem on /dev/datavg/datalv is now 7864320 (4k) blocks long.

# 场景：缩减逻辑卷和文件系统

# 1. 查看逻辑卷
# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
datalv datavg -wi-ao—- 50.00g
root rhel -wi-ao—- 45.00g
swap rhel -wi-ao—- 4.00g

# 2. 查看文件系统使用情况
# df -h /data
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/datavg-datalv 50G 10G 40G 20% /data

# 3. 卸载文件系统
# umount /data

# 4. 检查文件系统
# e2fsck -f /dev/datavg/datalv
e2fsck 1.46.5 (30-Dec-2021)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/datavg/datalv: 11/3276800 files (0.0% non-contiguous), 200000/13107200 blocks

# 5. 缩减ext4文件系统
# resize2fs /dev/datavg/datalv 40G
resize2fs 1.46.5 (30-Dec-2021)
Resizing the filesystem on /dev/datavg/datalv to 10485760 (4k) blocks.
The filesystem on /dev/datavg/datalv is now 10485760 (4k) blocks long.

# 6. 缩减逻辑卷
# lvreduce -L 40G /dev/datavg/datalv
WARNING: Reducing active logical volume to 40.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce datavg/datalv? [y/n]: y
Size of logical volume datavg/datalv changed from 50.00 GiB (12800 extents) to 40.00 GiB (10240 extents).
Logical volume datavg/datalv successfully resized.

# 7. 查看逻辑卷
# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
datalv datavg -wi-a—– 40.00g
root rhel -wi-ao—- 45.00g
swap rhel -wi-ao—- 4.00g

# 8. 挂载文件系统
# mount /dev/datavg/datalv /data

# 9. 验证文件系统大小
# df -h /data
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/datavg-datalv 40G 10G 30G 25% /data

# 10. 一键缩减
# umount /data
# lvreduce -L 30G -r /dev/datavg/datalv
WARNING: Reducing active and open logical volume to 30.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce datavg/datalv? [y/n]: y
Size of logical volume datavg/datalv changed from 40.00 GiB (10240 extents) to 30.00 GiB (7680 extents).
Logical volume datavg/datalv successfully resized.
resize2fs 1.46.5 (30-Dec-2021)
Resizing the filesystem on /dev/datavg/datalv to 7864320 (4k) blocks.
The filesystem on /dev/datavg/datalv is now 7864320 (4k) blocks long.

# 11. 挂载文件系统
# mount /dev/datavg/datalv /data

# 12. 验证文件系统大小
# df -h /data
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/datavg-datalv 30G 10G 20G 33% /data