1. Linux hard disk

1. Linux hard disk

1.1. Basic knowledge

But please remember:

One mount point mounts one device at the same time
A mount point mounts multiple devices at the same time, only the data of the last device can be seen, and the data on other devices will be hidden
A device can be mounted to multiple mount points at the same time
Usually the mount point is an existing empty directory

There are also some commonly used commands:

findmntThe command can check whether the folder has a mount point
lsofThe command can check whether a mount point is being used by someone
blkidCommand to view UUID
mount -a: The mount takes effect immediately
vim /etc/fstabEdit folder can modify permanent mount

1.1.1. Primary vs. Extended Partition

Difference	Primary partition	Extended partition
Quantity	At least 1 and a maximum of 4.	Cannot use extended partition directly. It is used as a logical partition so that the extended partition consists of several logical partitions.
Bootable	The primary partition is bootable, and it contains the operating system/s of the computer.	The extended partition is a partition that is not bootable.
Applicable scenarios (applicable scenarios)	We can use it to boot the operating system, establish one to four primary partitions and install multiple operating systems without interfering.	Extended partitions do not store files directly but create logical partitions to store general data, audio, pictures, and files.
Naming example	Primary partitions are assigned the first letters in the alphabet as drive letters (such as C, D).	Logical drives in the extended partition get the other letters (such as E, F, G).

1.2. Virtual machine hard disk expansion process

1.2.1. Problems found

Use a virtual machine to create a CentOS with a 300G hard disk, but when it comes in, it is only 35G:

# df - report file system disk space usage
df -h

Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root   35G  2.1G   33G   6% /
devtmpfs                 2.0G     0  2.0G   0% /dev
tmpfs                    2.0G     0  2.0G   0% /dev/shm
tmpfs                    2.0G  8.8M  2.0G   1% /run
tmpfs                    2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/sda1               1014M  133M  882M  14% /boot
tmpfs                    396M     0  396M   0% /run/user/0

# lsblk - list block devices
lsblk

NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0  300G  0 disk
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   39G  0 part
  ├─centos-root 253:0    0   35G  0 lvm  /
  └─centos-swap 253:1    0    4G  0 lvm  [SWAP]
sr0              11:0    1 1024M  0 rom

# fdisk - manipulate disk partition table
fdisk -l

Disk /dev/sda: 322.1 GB, 322122547200 bytes, 629145600 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: 0x000f1bd2

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200    83886079    40893440   8e  Linux LVM

Disk /dev/mapper/centos-root: 37.6 GB, 37576769536 bytes, 73392128 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 /dev/mapper/centos-swap: 4294 MB, 4294967296 bytes, 8388608 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

1.2.2. Start to adjust the partition

Bring back the lost space.

# 打开 sdb 盘进行分区
fdisk /dev/sda

m            # m for help
n            # add a new partition
[default]... # 一直按回车就可以了
p            # print the partition table
w            # write table to disk and exit

reboot

# ls /lib/modules/`uname -r`/kernel/fs    # 判断当前的内核支持哪些文件系统
# lsblk -f                                # 查看一下刚刚添加的文件系统
# mkfs.xfs /dev/sda3                      # 创建 ext4 的文件系统到硬盘 b 的 1 分区

# 给刚刚新建的分区 /dev/sda3 
# pvcreate - Initialize physical volume(s) for use by LVM
pvcreate /dev/sda3

# 查看 vg 组
# vgs - Display information about volume groups
vgs

# 扩展 vg
# vgextend - Add physical volumes to a volume group
vgextend centos /dev/sda3

# lvs - Display information about logical volumes
lvs

# lvextend - Add space to a logical volume
lvextend -l +100%FREE /dev/centos/root

# 使系统重新读取大小
# xfs_growfs, xfs_info - expand an XFS filesystem
xfs_growfs /dev/mapper/centos-root

reboot

reference:

Linux hard disk

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