才不是没东西写了呢

遇到一个奇葩的原因导致 root 分区被占满的。而且还是奇葩的 CentOS，root 分区是 LVM，Hypervisor 里扩展磁盘后无法直接用 resize2fs。

既然如此就只能暴力重建分区咯。

重建分区

操作前确保操作的分区和之后新建时 Start 保持一致，修改分区表后不至于分区崩坏。

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~> fidks /dev/sda
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): p

Disk /dev/sda: 103.1 GB, 103079215104 bytes, 201326592 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
Disk label type: dos
Disk identifier: 0x000a8e23

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200    50331647    24116224   8e  Linux LVM

Command (m for help): d
Partition number (1,2, default 2): 2
Partition 2 is deleted

Command (m for help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p):
Using default response p
Partition number (2-4, default 2):
First sector (2099200-201326591, default 2099200):
Using default value 2099200
Last sector, +sectors or +size{K,M,G} (2099200-201326591, default 201326591):
Using default value 201326591
Partition 2 of type Linux and of size 95 GiB is set

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

~> partprobe

现在就可以看到 /dev/sda2 的大小已经变化了：

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~> lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   96G  0 disk
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   95G  0 part
  ├─centos-root 253:0    0 20.6G  0 lvm  /
  └─centos-swap 253:1    0  2.4G  0 lvm  [SWAP]
sr0              11:0    1  906M  0 rom

扩展 Volume Group

VG 的好处也就是能够灵活扩展分区大小…

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~> pvresize /dev/sda2
  Physical volume "/dev/sda2" changed
  1 physical volume(s) resized / 0 physical volume(s) not resized
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~> vgdisplay
  --- Volume group ---
  VG Name               centos
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  4
  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               <95.00 GiB
  PE Size               4.00 MiB
  Total PE              24319
  Alloc PE / Size       5887 / <23.00 GiB
  Free  PE / Size       18432 / 72.00 GiB
  VG UUID               TpbtuH-AjTZ-PU3v-UN31-FvfX-kSLv-xLiJG7

至此已经可以看到 Free PE 的部分有多出的 72GB 空间。

扩展 Logic Volume

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~> lvextend -r -l +100%FREE /dev/centos/root
  Size of logical volume centos/root changed from 20.59 GiB (5272 extents) to 92.59 GiB (23704 extents).
  Logical volume centos/root successfully resized.
meta-data=/dev/mapper/centos-root isize=512    agcount=4, agsize=1349632 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0 spinodes=0
data     =                       bsize=4096   blocks=5398528, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal               bsize=4096   blocks=2636, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 5398528 to 24272896

确认效果：

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~> lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   96G  0 disk 
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   95G  0 part 
  ├─centos-root 253:0    0 92.6G  0 lvm  /
  └─centos-swap 253:1    0  2.4G  0 lvm  [SWAP]
sr0              11:0    1  906M  0 rom

~> df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root   93G   21G   73G  23% /
devtmpfs                 3.9G     0  3.9G   0% /dev
tmpfs                    3.9G  8.0K  3.9G   1% /dev/shm
tmpfs                    3.9G  8.6M  3.9G   1% /run
tmpfs                    3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/sda1               1014M  185M  830M  19% /boot
tmpfs                    783M     0  783M   0% /run/user/0

搞定收工(‘・ω・’)

后话

其实虚拟机还用 LVM 的话，直接新增一块虚拟硬盘是最方便的方案。直接 vgextend 一路搞定…