Reducing linux file system

How to Shrink XFS File System on Enterprise Linux 7.2

Why cannot we just lvreduce XFS file system? A quote from Red Hat official document talking about XFS space management may explain the whole thing.

XFS is a highly scalable, high-performance file system which was originally designed at Silicon Graphics, Inc. XFS is the default file system for Red Hat Enterprise Linux 7 .

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After an XFS file system is created, its size cannot be reduced . However, it can still be enlarged using the xfs_growfs command (refer to Section 6.4, “Increasing the Size of an XFS File System”).

lvreduce XFS?

It’s true, but the scalability of XFS is only for scaling up, not for scaling down. What if we need to shrink a mount point which was mis-allocated with too much space (I know this would rarely happen on most production environments). Can we just reclaim some space back? The answer is No and Yes.

The «No» is that we cannot reduce XFS logical volume (LV) directly just by handy lvreduce or something else. The «Yes» is that we can work around it, but the approach might be a little tricky.

If your file systems are formatted as any of legacy ext series, you may refer to the post below for resolutions: How to Reduce Logical Volume Size on Linux

Steps to Shrink XFS File System

1. Create a file for verifying after reducing XFS size

Log in server as a normal user, i.e. edchen in this case.

[edchen@test ~]$ pwd
/home/edchen
[edchen@test ~]$ vi Hello
Hello, world!
[edchen@test ~]$ ll
total 4
-rw-rw-r—. 1 edchen edchen 14 Mar 24 00:03 Hello
[edchen@test ~]$ exit

2. Check current status

Let’s see the space usage.
[root@test ~]# df -h | grep home
/dev/mapper/centos_example-home 188G 33M 188G 1% /home
[root@test ~]# vgs
VG #PV #LV #SN Attr VSize VFree
centos_example 1 3 0 wz—n- 239.51g 64.00m
[root@test ~]# lvdisplay
.
— Logical volume —
LV Path /dev/centos_example/home
LV Name home
VG Name centos_example
LV UUID
LV Write Access read/write
LV Creation host, time test.com, 2016-03-21 08:27:22 -0400
LV Status available
# open 1
LV Size 187.45 GiB
Current LE 47986
Segments 1
Allocation inherit
Read ahead sectors auto
— currently set to 8192
Block device 253:2

You can see that /home is taking too much free space without using it. We need to shrink this XFS logical volume /dev/centos_example/home .

[root@test ~]# mount | grep home
/dev/mapper/centos_example-home on /home type xfs (rw,relatime,seclabel,attr2,inode64,noquota)

See? It’s a XFS LV mounted. Since XFS does not allow to shrink its size, so we need a strategy to workaround this. Of course, we don’t want to reinstall OS. Here is my plan in short:

1. Backup the data
2. Remove current LV
3. Create a smaller LV
4. Restore the data

Let’s see how far we can go.

3. Install XFS backup utilities

The best tool to backup XFS file system is xfsdump . Since there’s no xfsdump in CentOS 7.2 minimal, so we have to install it by ourselves. First of all, let’s see what is xfsdump .

[root@test ~]# yum info xfsdump
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: ftp.ksu.edu.tw
* epel: mirror01.idc.hinet.net
* extras: ftp.ksu.edu.tw
* updates: centos.cs.nctu.edu.tw
* webtatic: sp.repo.webtatic.com
Available Packages
Name : xfsdump
Arch : x86_64
Version : 3.1.4
Release : 1.el7
Size : 307 k
Repo : base/7/x86_64
Summary : Administrative utilities for the XFS filesystem
URL : http://oss.sgi.com/projects/xfs/
License : GPL+
Description : The xfsdump package contains xfsdump, xfsrestore and a number of
: other utilities for administering XFS filesystems.
:
: xfsdump examines files in a filesystem, determines which need to
: be backed up, and copies those files to a specified disk, tape or
: other storage medium. It uses XFS-specific directives for
: optimizing the dump of an XFS filesystem, and also knows how to
: backup XFS extended attributes. Backups created with xfsdump are
: «endian safe» and can thus be transfered between Linux machines of
: different architectures and also between IRIX machines.
:
: xfsrestore performs the inverse function of xfsdump; it can
: restore a full backup of a filesystem. Subsequent incremental
: backups can then be layered on top of the full backup. Single
: files and directory subtrees may be restored from full or partial
: backups.

Install xfsdump package which also includes xfsrestore

[root@test ~]# yum -y install xfsdump
Loaded plugins: fastestmirror
base | 3.6 kB 00:00
epel/x86_64/metalink | 5.2 kB 00:00
extras | 3.4 kB 00:00
mysql-connectors-community | 2.5 kB 00:00
mysql-tools-community | 2.5 kB 00:00
mysql57-community | 2.5 kB 00:00
updates | 3.4 kB 00:00
webtatic | 3.6 kB 00:00
updates/7/x86_64/primary_db | 3.2 MB 00:20
Loading mirror speeds from cached hostfile
* base: ftp.ksu.edu.tw
* epel: mirror01.idc.hinet.net
* extras: ftp.ksu.edu.tw
* updates: centos.cs.nctu.edu.tw
* webtatic: us-east.repo.webtatic.com
Resolving Dependencies
—> Running transaction check
—> Package xfsdump.x86_64 0:3.1.4-1.el7 will be installed
—> Processing Dependency: attr >= 2.0.0 for package: xfsdump-3.1.4-1.el7.x86_64
—> Running transaction check
—> Package attr.x86_64 0:2.4.46-12.el7 will be installed
—> Finished Dependency Resolution

Total download size: 373 k
Installed size: 1.1 M
Downloading packages:
(1/2): attr-2.4.46-12.el7.x86_64.rpm | 66 kB 00:00
(2/2): xfsdump-3.1.4-1.el7.x86_64.rpm | 307 kB 00:02
———————————————————————————
Total 145 kB/s | 373 kB 00:02
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : attr-2.4.46-12.el7.x86_64 1/2
Installing : xfsdump-3.1.4-1.el7.x86_64 2/2
Verifying : attr-2.4.46-12.el7.x86_64 1/2
Verifying : xfsdump-3.1.4-1.el7.x86_64 2/2

Installed:
xfsdump.x86_64 0:3.1.4-1.el7

Dependency Installed:
attr.x86_64 0:2.4.46-12.el7

4. Backup the XFS file system

We backup the XFS file system to a regular file in the root directory / which will stay everything unchanged in this tutorial. The -l option specifies a dump level (0-9). To perform a full backup, use 0 . The -f option specifies the destination of target and source, the format is:

[root@test ~]# xfsdump -l 0 -f /home.image /dev/centos_example/home
xfsdump: using file dump (drive_simple) strategy
xfsdump: version 3.1.4 (dump format 3.0) — type ^C for status and control

please enter label for this dump session (timeout in 300 sec)
-> 20160324-dump
session label entered: «20160324-dump»

xfsdump: level 0 dump of test.com:/home
xfsdump: dump date: Thu Mar 24 00:06:49 2016
xfsdump: session id: 7fe1566a-de11-45f2-93c5-85a9b4725a27
xfsdump: session label: «20160324-dump»
xfsdump: ino map phase 1: constructing initial dump list
xfsdump: ino map phase 2: skipping (no pruning necessary)
xfsdump: ino map phase 3: skipping (only one dump stream)
xfsdump: ino map construction complete
xfsdump: estimated dump size: 20800 bytes
xfsdump: /var/lib/xfsdump/inventory created

please enter label for media in drive 0 (timeout in 300 sec)
-> home-old
media label entered: «home-old»

xfsdump: creating dump session media file 0 (media 0, file 0)
xfsdump: dumping ino map
xfsdump: dumping directories
xfsdump: dumping non-directory files
xfsdump: ending media file
xfsdump: media file size 21352 bytes
xfsdump: dump size (non-dir files) : 0 bytes
xfsdump: dump complete: 20 seconds elapsed
xfsdump: Dump Summary:
xfsdump: stream 0 /home.image OK (success)
xfsdump: Dump Status: SUCCESS

[root@test ~]# ll /home.image
-rw-r—r—. 1 root root 21352 Mar 24 00:07 /home.image

5. Remove the source LV

We should umount the file system before doing anything on the LV.

[root@test ~]# umount /dev/centos_example/home

Use lvremove to delete the LV.

[root@test ~]# lvremove /dev/centos_example/home
Do you really want to remove active logical volume home? [y/n]: y
Logical volume «home» successfully removed
[root@test ~]# vgs
VG #PV #LV #SN Attr VSize VFree
centos_example 1 2 0 wz—n- 239.51g 187.51g

As you can see, the space is released.

6. Create a new LV

Use lvcreate to create a 10GB with the same name.

[root@test ~]# lvcreate -L 10G -n home centos_example
WARNING: xfs signature detected on /dev/centos_example/home at offset 0. Wipe it? [y/n]: y
Wiping xfs signature on /dev/centos_example/home.
Logical volume «home» created.

The signature is replaced with the new one. Let’s see the current status of VG and LV.

[root@test ~]# vgs
VG #PV #LV #SN Attr VSize VFree
centos_example 1 3 0 wz—n- 239.51g 177.51g
[root@test ~]# lvdisplay
.
— Logical volume —
LV Path /dev/centos_example/home
LV Name home
VG Name centos_example
LV UUID
LV Write Access read/write
LV Creation host, time test.com, 2016-03-24 00:10:45 -0400
LV Status available
# open 0
LV Size 10.00 GiB
Current LE 2560
Segments 1
Allocation inherit
Read ahead sectors auto
— currently set to 8192
Block device 253:2

There’s a 10GB taken by the new LV. Now, we have to format the new LV in XFS by mkfs.xfs before actually mounting on /home .

[root@test ~]# mkfs.xfs /dev/centos_example/home
meta-data=/dev/centos_example/home isize=256 agcount=4, agsize=655360 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0 finobt=0
data = bsize=4096 blocks=2621440, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal log bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0

[root@test ~]# mount /dev/centos_example/home /home

[root@test ~]# ll /home
total 0

Of course, nothing in the /home , because we have not restored the data yet.

7. Restore data back to the new and smaller XFS file system

[root@test ~]# xfsrestore -f /home.image /home
xfsrestore: using file dump (drive_simple) strategy
xfsrestore: version 3.1.4 (dump format 3.0) — type ^C for status and control
xfsrestore: searching media for dump
xfsrestore: examining media file 0
xfsrestore: dump description:
xfsrestore: hostname: test.com
xfsrestore: mount point: /home
xfsrestore: volume: /dev/mapper/centos_example-home
xfsrestore: session time: Thu Mar 24 00:06:49 2016
xfsrestore: level: 0
xfsrestore: session label: «20160324-dump»
xfsrestore: media label: «home-old»
xfsrestore: file system id: 091dc119-8bae-42ac-a725-4a79196398c9
xfsrestore: session id: 7fe1566a-de11-45f2-93c5-85a9b4725a27
xfsrestore: media id: d07cadad-8e5e-4767-bf52-e256dc060e5d
xfsrestore: using online session inventory
xfsrestore: searching media for directory dump
xfsrestore: reading directories
xfsrestore: 1 directories and 0 entries processed
xfsrestore: directory post-processing
xfsrestore: restore complete: 1 seconds elapsed
xfsrestore: Restore Summary:
xfsrestore: stream 0 /home.image OK (success)
xfsrestore: Restore Status: SUCCESS

[root@test ~]# ll /home
total 0
drwx——. 2 edchen edchen 71 Mar 24 00:01 edchen
[root@test ~]# df -h | grep home
/dev/mapper/centos_example-home 10G 33M 10G 1% /home
[root@test ~]# mount | grep home
/dev/mapper/centos_example-home on /home type xfs (rw,relatime,seclabel,attr2,inode64,noquota)

So far so good, we have the content back to /home . But I have a question now: Can it survive through reboots? Let’s continue.

8. Verify the data after reducing XFS LV size

Log in server as edchen and verify the file.

[edchen@test ~]$ ll
total 4
-rw-rw-r—. 1 edchen edchen 14 Mar 24 00:03 Hello
[edchen@test ~]$ cat Hello
Hello, world!

Источник

How to Shrink an ext2/3/4 File system with resize2fs

1. If the partition the file system is on is currently mounted, unmount it.

2. Run fsck on the unmounted file system.

~]# e2fsck /dev/vdb1 e2fsck 1.41.12 (17-May-2010) 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 sumary information ext4-1:11/131072 files (0.0% non-contiguous),27050/524128 blocks 

3. Shrink the file system with the resize2fs /dev/device size command.

~]# resize2fs /dev/vdb1 200M resize2fs 1.41.12 (17-May-2010) Resizing the filesystem on /dev/vdb1 to 204800 (1k) blocks. The filesystem /dev/vdb1 is now 204800 blocks long. 

Accepted size units for file system block sizes are:

4. Delete and recreate the partition the file system is on to the required amount. If the file system is smaller than 2TB use fdisk as is described in How to Resize a File System with fdisk, if the file system is larger than 2TB use parted as described in [LINK TO COME].

5. Mount the file system and partition.

More Information

man resize2fs – man page for resize2fs that contains information on what resize2fs is, what it supports, and the various options it takes.

Источник