LVM（Logical Volume Manager）

April 16, 2017

—

什麼是 LVM

可彈性調整檔案磁區大小
- Physical Volume, PV（實體卷宗）
- Volume Group, VG（卷宗群組）
- Logical Volume, LV（邏輯卷宗）

非效能取向
寫入方式
- 線性（預設）
  - A partition 用完時，在使用 B partition
- 交錯（像 RAID 0）
  - 一份資料用兩顆硬碟來寫入的概念

LVM 可以整合多個實體 partition 在一起，讓這些 partitions 看起來就像是一個磁碟一樣。還可以在未來新增或移除其他的實體 partition 到這個 LVM 管理的磁碟當中。 by 鳥歌

Physical Volume, PV

利用 fdisk 將劃分的硬碟調整 system ID 為 8e

pvcreate
- 將實體磁區建立為 PV
pvscan
- 列出系統中 PV 磁區
pvdisplay
- 顯示系統上 PV 狀態
pvremove
- 將 PV 屬性移除

Volume Group, VG

VG 就是 LVM 組合起來的大磁碟，多個 PV 組合而成。

vgcreate
- 建立 VG
vgscan
- 列出系統中 VG 的卷區
vgdisplay
- 顯示系統上 VG 狀態
vgremove
- 將 VG 移除
vgextend
- VG 內新增加額外 PV
vgreduce
- 在 VG 內移除 PV
vgchange
- 設定 VG 是否啟動

Logical Volume, LV

最後用來格式化，建立分割區，最後裝置名稱為 /dev/vg_NAME/lv_name

lvcreate
- 建立 LV
- –size 設定大小
- -n 設定名稱
- -p 設定存取權限（r、rw）
- -s 設定快照
lvscan
- 列出系統中 LV 的卷區
lvdisplay
- 顯示系統中 LV 狀態
lvremove
- 將 LV 移除
lvextend
- LV 內增加容量
lvreduce
- LV 內減少容量
lvresize
- 調整 LV 容量大小

PV、VG、LV 整理

“鳥歌”

實作

/dev/sdb 新增一顆 1GB 硬碟，切分三個 LVM 磁區分別為 100 MB。

以下是變換預設磁區為 LVM

Command (m for help): t
Partition number (1-3, default 3): 1
Partition type (type L to list all types): 8e

Changed type of partition 'Linux' to 'Linux LVM'.

Command (m for help): t
Partition number (1-3, default 3): 2
Partition type (type L to list all types): 8e

Changed type of partition 'Linux' to 'Linux LVM'.

Command (m for help): t
Partition number (1-3, default 3): 3
Partition type (type L to list all types): 8e

Changed type of partition 'Linux' to 'Linux LVM'.

Command (m for help): p
Disk /dev/sdb: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x49871a65

Device     Boot  Start    End Sectors  Size Id Type
/dev/sdb1         2048 206847  204800  100M 8e Linux LVM
/dev/sdb2       206848 411647  204800  100M 8e Linux LVM
/dev/sdb3       411648 616447  204800  100M 8e Linux LVM

建立三組 PV

$ for i in $(seq 1 3) ; do sudo pvcreate /dev/sdb$i; done
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdb2" successfully created
  Physical volume "/dev/sdb3" successfully created

掃瞄檢查 PV 狀態

$ sudo pvscan
  PV /dev/sda5   VG ubuntu-vg       lvm2 [19.52 GiB / 916.00 MiB free]
  PV /dev/sdb3                      lvm2 [100.00 MiB]
  PV /dev/sdb1                      lvm2 [100.00 MiB]
  PV /dev/sdb2                      lvm2 [100.00 MiB]
  Total: 4 [19.81 GiB] / in use: 1 [19.52 GiB] / in no VG: 3 [300.00 MiB]
$ sudo pvdisplay /dev/sdb1
  "/dev/sdb1" is a new physical volume of "100.00 MiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdb1
  VG Name
  PV Size               100.00 MiB
  Allocatable           NO
  PE Size               0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               gzH4Bq-9csW-FSRP-jSvy-pOvf-0D0S-W8mVpx

建立 VG

建立一組 VG，名稱為 bossvg 並將 /dev/sdb1 和 /dev/sdb2 加入

$ sudo vgcreate bossvg /dev/sdb1
  Volume group "bossvg" successfully created
$ sudo vgextend bossvg /dev/sdb2
  Volume group "bossvg" successfully extended

$ sudo vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "ubuntu-vg" using metadata type lvm2
  Found volume group "bossvg" using metadata type lvm2
cch@ubuntu:~$ sudo vgdisplay
  --- Volume group ---
  VG Name               ubuntu-vg
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               19.52 GiB
  PE Size               4.00 MiB
  Total PE              4997
  Alloc PE / Size       4768 / 18.62 GiB
  Free  PE / Size       229 / 916.00 MiB
  VG UUID               Nc3WGO-0HbI-rht1-YtjR-78be-deZp-Ezc2dM

  --- Volume group ---
  VG Name               bossvg
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               192.00 MiB
  PE Size               4.00 MiB
  Total PE              48
  Alloc PE / Size       0 / 0
  Free  PE / Size       48 / 192.00 MiB
  VG UUID               fPJc75-tztw-Qszi-n9t9-5mfO-Vehn-F2WO9u
$ sudo pvscan
  PV /dev/sda5   VG ubuntu-vg       lvm2 [19.52 GiB / 916.00 MiB free]
  PV /dev/sdb1   VG bossvg          lvm2 [96.00 MiB / 96.00 MiB free]
  PV /dev/sdb2   VG bossvg          lvm2 [96.00 MiB / 96.00 MiB free]
  PV /dev/sdb3                      lvm2 [100.00 MiB]
  Total: 4 [19.80 GiB] / in use: 3 [19.71 GiB] / in no VG: 1 [100.00 MiB]

建立一組 LV

從 bossvg 分出 130 MB 給 bosslv，並格式化，將他 mount 至 /mnt/templv

$ sudo lvcreate --size 130MB -n bosslv bossvg
  Rounding up size to full physical extent 132.00 MiB
  Logical volume "bosslv" created.
$ sudo lvscan
  ACTIVE            '/dev/ubuntu-vg/root' [17.67 GiB] inherit
  ACTIVE            '/dev/ubuntu-vg/swap_1' [976.00 MiB] inherit
  ACTIVE            '/dev/bossvg/bosslv' [132.00 MiB] inherit
$ sudo lvdisplay
  --- Logical volume ---
  LV Path                /dev/ubuntu-vg/root
  LV Name                root
  VG Name                ubuntu-vg
  LV UUID                do4I3J-zub8-7rGz-h0vn-LENG-TlsX-agNYfm
  LV Write Access        read/write
  LV Creation host, time ubuntu, 2018-11-27 21:21:14 +0800
  LV Status              available
  # open                 1
  LV Size                17.67 GiB
  Current LE             4524
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:0

  --- Logical volume ---
  LV Path                /dev/ubuntu-vg/swap_1
  LV Name                swap_1
  VG Name                ubuntu-vg
  LV UUID                DtptD7-aHhN-oqr1-fhRa-ZkSy-39HN-O13099
  LV Write Access        read/write
  LV Creation host, time ubuntu, 2018-11-27 21:21:15 +0800
  LV Status              available
  # open                 2
  LV Size                976.00 MiB
  Current LE             244
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:1

  --- Logical volume ---
  LV Path                /dev/bossvg/bosslv
  LV Name                bosslv
  VG Name                bossvg
  LV UUID                fb7AXW-sj3u-Ut2r-SGJf-03Kl-dyFB-lUjzkI
  LV Write Access        read/write
  LV Creation host, time ubuntu, 2019-09-01 00:57:10 +0800
  LV Status              available
  # open                 0
  LV Size                132.00 MiB
  Current LE             33
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           252:2

格式化

$ sudo mkfs.ext4 /dev/bossvg/bosslv
mke2fs 1.42.13 (17-May-2015)
Creating filesystem with 135168 1k blocks and 33864 inodes
Filesystem UUID: b652f4b2-5903-4c17-a6e1-86d71b41bcfe
Superblock backups stored on blocks:
        8193, 24577, 40961, 57345, 73729

Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

掛載

$ sudo mkdir /mnt/templv
cch@ubuntu:~$ sudo mount /dev/bossvg/bosslv /mnt/templv/
cch@ubuntu:~$ ls /mnt/templv/
lost+found
$ df -Th /mnt/templv/
Filesystem                Type  Size  Used Avail Use% Mounted on
/dev/mapper/bossvg-bosslv ext4  124M  1.6M  114M   2% /mnt/templv

VG 放大

再新增 30MB 空間

$ sudo lvresize --size +30MB /dev/bossvg/bosslv
  Rounding size to boundary between physical extents: 32.00 MiB
  Size of logical volume bossvg/bosslv changed from 132.00 MiB (33 extents) to 164.00 MiB (41 extents).
  Logical volume bosslv successfully resized.
$ sudo vgdisplay; sudo lvscan
  --- Volume group ---
  VG Name               ubuntu-vg
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               19.52 GiB
  PE Size               4.00 MiB
  Total PE              4997
  Alloc PE / Size       4768 / 18.62 GiB
  Free  PE / Size       229 / 916.00 MiB
  VG UUID               Nc3WGO-0HbI-rht1-YtjR-78be-deZp-Ezc2dM

  --- Volume group ---
  VG Name               bossvg
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               192.00 MiB
  PE Size               4.00 MiB
  Total PE              48
  Alloc PE / Size       41 / 164.00 MiB
  Free  PE / Size       7 / 28.00 MiB
  VG UUID               fPJc75-tztw-Qszi-n9t9-5mfO-Vehn-F2WO9u

  ACTIVE            '/dev/ubuntu-vg/root' [17.67 GiB] inherit
  ACTIVE            '/dev/ubuntu-vg/swap_1' [976.00 MiB] inherit
  ACTIVE            '/dev/bossvg/bosslv' [164.00 MiB] inherit

移除 LVM 流程

先卸載系統上面的 LVM 檔案系統 (包括快照與所有 LV)；
使用 lvremove 移除 LV ；
使用 vgchange -a n VGname 讓 VGname 這個 VG 不具有 Active 的標誌；
使用 vgremove 移除 VG：
使用 pvremove 移除 PV；
最後，使用 fdisk 修改 ID 回來啊！

By 鳥歌

參考

鳥歌 LVM

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