练习 19:文件系统:挂载,mount/etc/fstab

原文:Exercise 19. Filesystems: mounting, mount, /etc/fstab

译者:飞龙

协议:CC BY-NC-SA 4.0

自豪地采用谷歌翻译

我希望你熟悉分区的概念。如果没有,我会简要介绍一下。首先引用自维基百科:

磁盘分区是一种行为,将硬盘驱动器分为多个逻辑存储单元,它们被称为分区,来将一个物理磁盘驱动器视为多个磁盘。

看一看:

user1@vm1:~$ sudo parted /dev/vda
GNU Parted 2.3
Using /dev/vda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) unit GB
(parted) p
Model: Virtio Block Device (virtblk)
Disk /dev/vda: 17.2GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type      File system     Flags
 1      0.00GB  13.3GB  13.3GB  extended
 5      0.00GB  1.02GB  1.02GB  logical   ext3            boot
 6      1.03GB  2.05GB  1.02GB  logical   linux-swap(v1)
 7      2.05GB  3.07GB  1.02GB  logical   ext3
 8      3.07GB  5.12GB  2.05GB  logical   ext3
 9      5.12GB  9.22GB  4.09GB  logical   ext3
10      9.22GB  13.3GB  4.09GB  logical   ext3

(parted)

这是一个物理硬盘,分为 7 个不同的分区。这样做的原因很多,但最好被理解为“分治”原则的应用。以这种方式分割时,流氓程序不能通过占用所有磁盘空间,使整个服务器崩溃,该程序将限制在其分区中。我不会再谈论磁盘分区,但是我会继续关注文件系统,再次引用维基百科

文件系统是一种组织数据的手段。通过提供存储,检索和更新数据的过程,以及管理包含它的设备上的可用空间,数据预期在程序终止后保留。文件系统以有效的方式组织数据,并根据设备的特定特性进行调整。在操作系统和文件系统之间,通常存在紧耦合。一些文件系统提供了机制来控制数据和元数据的访问。确保可靠性是文件系统的主要职责。一些文件系统允许多个程序几乎同时更新同一个文件。

类 Unix 操作系统创建一个虚拟文件系统,这使得所有设备上的所有文件似乎都存在于单个层次结构中。这意味着,在这些系统中,有一个根目录,系统上存在的每个文件位于它下方的某个地方。类 Unix 系统可以使用 RAM 磁盘或网络共享资源作为其根目录。

这意味着,所有文件系统都集成在一个大树中。对于熟悉 Microsoft Windows 的人来说,这意味着比起C:\D:\等盘符,这种命名方案有一个单独的根,/,所有其他分区都连接到它上面。将文件系统连接到现有目录的过程称为挂载。连接文件系统的目录称为挂载点。同样,看一看:

user1@vm1:~$ mount
/dev/vda5 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/vda10 on /home type ext3 (rw)
/dev/vda7 on /tmp type ext3 (rw)
/dev/vda9 on /usr type ext3 (rw)
/dev/vda8 on /var type ext3 (rw)

这是我之前展示给你的相同分区,你可以在这个列表中看到挂载点。不以/dev/vda开头的是虚拟文件系统,它允许访问不同的系统设施,但它们和此练习无关。现在我们来看看/etc/fstab文件:

user1@vm1:~$ cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    defaults    0       0
# / was on /dev/vda5 during installation
UUID=128559db-a2e0-4983-91ad-d4f43f27da49 /         ext3    errors=remount-ro 0       1
# /home was on /dev/vda10 during installation
UUID=32852d29-ddee-4a8d-9b1e-f46569a6b897 /home     ext3    defaults        0       2
# /tmp was on /dev/vda7 during installation
UUID=869db6b4-aea0-4a25-8bd2-f0b53dd7a88e /tmp      ext3    defaults        0       2
# /usr was on /dev/vda9 during installation
UUID=0221be16-496b-4277-b131-2371ce097b44 /usr      ext3    defaults        0       2
# /var was on /dev/vda8 during installation
UUID=2db00f94-3605-4229-8813-0ee23ad8634e /var      ext3    defaults        0       2
# swap was on /dev/vda6 during installation
UUID=3a936af2-2c04-466d-b98d-09eacc5d104c none      swap    sw              0       0
/dev/scd0       /media/cdrom0   udf,iso9660 user,noauto     0       0

看起来很恐怖,但让我们选取一行:

# <file system>                             <mount point>  <type>  <options>         <dump>  <pass>
UUID=128559db-a2e0-4983-91ad-d4f43f27da49   /              ext3    errors=remount-ro 0       1

按照字段将其拆开。

UUID=128559db-a2e0-4983-91ad-d4f43f27da49 # Filesystem to mount. This UUID is synonim for /dev/vda5
/                    # This is root filesystem, mount it to /
ext3                 # This is ext3 filesystem. There are many different filesystems out there
errors=remount-ro    # If any errors encountered during mounting filesystem should be remounted read-only
0                    # This filesystem should not be backed up by dump utility
1                    # This filesystem should be checked first by fsck utility

和之前一样,这些信息可以通过man fstab提供给你。现在我将向你展示使用现有文件系统的几个命令:

  • mount - 打印出所有已挂载的文件系统。
  • mount -a - 挂载/etc/fstab中描述的所有文件系统。
  • mount /dev/sda<N> /<mount point> - 挂载分区。
  • umount /dev/sda<N> /<mount point> - 解除挂载分区。
  • mount -h - 打印出使用mount的简短帮助。
  • fsck - 检查分区是否有错误。
  • blkid - 打印出唯一的分区标识符。

现在,你将学习如何列出已安装的分区,挂载和解除挂载它们。

这样做

1: cat /etc/fstab
2: mount
3: sudo blkid
4: sudo umount /tmp
5: mount
6: sudo fsck /tmp
7: sudo mount -a
8: mount

你会看到什么

user1@vm1:~$ cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    defaults        0       0
# / was on /dev/sda1 during installation
UUID=05d469bb-dbfe-4d5a-9bb2-9c0fe9fa8577 /               ext3    errors=remount-ro 0       1
# /home was on /dev/sda9 during installation
UUID=a1b936a0-df38-4bf5-b095-6220ffdfc63c /home           ext3    defaults        0       2
# /tmp was on /dev/sda8 during installation
UUID=d0a86453-0dbb-4f33-a023-6c09fe9fa202 /tmp ext3 defaults 0 2
# /usr was on /dev/sda5 during installation
UUID=b9544cbb-cdb6-4f3b-89e7-a339f52bfac7 /usr            ext3    defaults        0       2
# /var was on /dev/sda6 during installation
UUID=e15e713b-5850-4bc3-b99e-ab6f1d037caa /var            ext3    defaults        0       2
# swap was on /dev/sda7 during installation
UUID=4d516f09-80ff-4956-8a75-e9757697f6b1 none            swap    sw              0       0
/dev/scd0       /media/cdrom0   udf,iso9660 user,noauto     0       0
user1@vm1:~$ mount
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/sda9 on /home type ext3 (rw)
/dev/sda5 on /usr type ext3 (rw)
/dev/sda6 on /var type ext3 (rw)
/dev/sda8 on /tmp type ext3 (rw)
/dev/sda8 on /tmp type ext3 (rw)
user1@vm1:~$ sudo blkid
/dev/sda1: UUID="05d469bb-dbfe-4d5a-9bb2-9c0fe9fa8577" TYPE="ext3"
/dev/sda5: UUID="b9544cbb-cdb6-4f3b-89e7-a339f52bfac7" TYPE="ext3"
/dev/sda6: UUID="e15e713b-5850-4bc3-b99e-ab6f1d037caa" TYPE="ext3"
/dev/sda7: UUID="4d516f09-80ff-4956-8a75-e9757697f6b1" TYPE="swap"
/dev/sda8: UUID="d0a86453-0dbb-4f33-a023-6c09fe9fa202" TYPE="ext3"
/dev/sda9: UUID="a1b936a0-df38-4bf5-b095-6220ffdfc63c" TYPE="ext3"
user1@vm1:~$ sudo umount /tmp
user1@vm1:~$ mount
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/sda9 on /home type ext3 (rw)
/dev/sda5 on /usr type ext3 (rw)
/dev/sda6 on /var type ext3 (rw)
user1@vm1:~$ sudo fsck /tmp
fsck from util-linux-ng 2.17.2
e2fsck 1.41.12 (17-May-2010)
/dev/sda8: clean, 11/61752 files, 13973/246784 blocks
user1@vm1:~$ sudo mount -a
user1@vm1:~$ mount
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/sda9 on /home type ext3 (rw)
/dev/sda5 on /usr type ext3 (rw)
/dev/sda6 on /var type ext3 (rw)
/dev/sda8 on /tmp type ext3 (rw)
user1@vm1:~$

解释

  1. 打印你的/etc/fstab文件的内容,它包含分区信息以及挂载位置。
  2. 打印当前已挂载的分区。
  3. 打印系统中所有分区的 UUID。
  4. 解除挂载/tmp分区,以便你可以检查它。
  5. 再次打印出当前已挂载的分区。/tmp现在不存在于此列表中。
  6. 检查/tmp分区是否有错误。fsck通过读取相应的/etc/fstab条目知道要检查哪个分区。
  7. 挂载/etc/fstab中描述的所有分区。
  8. 再次打印当前已挂载的分区。/tmp已经返回了此列表。

附加题

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