RHCSA 01 - 创建分区与文件系统

Posted 2022-07-04 王万林 Ben

前言

本文演示创建一个loop文件，并将其分区、格式化，并挂载。

什么是loop设备？

loop设备是一个伪磁盘，它使用image文件作为其存储后端。 Linux dd 程序提供了一个简单的工具来创建此image文件。

实践

步骤1：查看根目录有大于10GB的剩余空间，

[root@e2b15ffb7e40 ~]# df -h /
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/rl-root   35G  1.9G   33G   6% /

步骤2：使用dd命令创建一个image文件，

[root@e2b15ffb7e40 ~]# dd if=/dev/zero of=/root/diskfile.img bs=1M count=8192
8192+0 records in
8192+0 records out
8589934592 bytes (8.6 GB, 8.0 GiB) copied, 13.7321 s, 626 MB/s
[root@e2b15ffb7e40 ~]# du -hs diskfile.img
8.0G    diskfile.img

步骤3：使用losetup工具，将该image文件设置为loop设备，

[root@e2b15ffb7e40 ~]# losetup -fP diskfile.img
[root@e2b15ffb7e40 ~]# losetup -a #查看
/dev/loop0: [64768]:67202764 (/root/diskfile.img)

步骤4：分区。Linux下有多个命令可以完成磁盘分区，这里使用fdisk，

[root@63655177b41a ~]# fdisk /dev/loop0

Welcome to fdisk (util-linux 2.32.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0x1f69de20.

Command (m for help): p
Disk /dev/loop0: 8 GiB, 8589934592 bytes, 16777216 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: 0x1f69de20

Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-16777215, default 2048): 
Last sector, +sectors or +sizeK,M,G,T,P (2048-16777215, default 16777215): +2G

Created a new partition 1 of type 'Linux' and of size 2 GiB.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

[root@63655177b41a ~]# lsblk
NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
loop0         7:0    0    8G  0 loop 
└─loop0p1   259:0    0    2G  0 loop 
sr0          11:0    1 1024M  0 rom  
vda         252:0    0 40.1G  0 disk 
├─vda1      252:1    0    1G  0 part /boot
└─vda2      252:2    0 38.1G  0 part 
  ├─rl-root 253:0    0 34.2G  0 lvm  /
  └─rl-swap 253:1    0  3.9G  0 lvm  [SWAP]
vdb         252:16   0    5G  0 disk 

步骤5：格式化分区

[root@63655177b41a ~]# mkfs.xfs /dev/loop0p1
meta-data=/dev/loop0p1           isize=512    agcount=4, agsize=131072 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1
data     =                       bsize=4096   blocks=524288, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
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
Discarding blocks...Done.

步骤6：挂载

[root@63655177b41a ~]# mount /dev/loop0p1 /mnt
[root@63655177b41a ~]# lsblk
NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
loop0         7:0    0    8G  0 loop 
└─loop0p1   259:0    0    2G  0 loop /mnt
sr0          11:0    1 1024M  0 rom  
vda         252:0    0 40.1G  0 disk 
├─vda1      252:1    0    1G  0 part /boot
└─vda2      252:2    0 38.1G  0 part 
  ├─rl-root 253:0    0 34.2G  0 lvm  /
  └─rl-swap 253:1    0  3.9G  0 lvm  [SWAP]
vdb         252:16   0    5G  0 disk 
[root@63655177b41a ~]# mount | grep /mnt
/dev/loop0p1 on /mnt type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,noquota)
[root@63655177b41a ~]# 

步骤7：使用

[root@63655177b41a ~]# echo "A test file." > /mnt/test.txt
[root@63655177b41a ~]# cat /mnt/test.txt
A test file.
[root@63655177b41a ~]# 

参考资料

https://man7.org/linux/man-pages/man4/loop.4.html#:~:text=The%20loop%20device%20is%20a,or%20to%20another%20block%20device.