In Linux, mount means "mounting" and is used to associate the device file system and the Linux file system through the specified directory; the syntax is "mount [-t system type] [-L volume name] [-o special option] [-n] device file name mount point", "mount -a", etc.

#The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

In the Linux system, "everything is a file", and all files are placed in a tree directory structure with the root directory as the root. From Linux's perspective, any hardware device is also a file, and each of them has its own file system (file directory structure).

The problem that arises is that when using these hardware devices in a Linux system, the hardware device can only be used by us if the file directory of Linux itself and the file directory of the hardware device are combined into one. The process of combining the two into one is called "mounting".

Mounting refers to connecting the top-level directory in the device file to a directory under the Linux root directory (preferably an empty directory). Accessing this directory is equivalent to accessing the device file.

Mounting refers to associating the file system of the hardware device with the file system in the Linux system by specifying the directory (as the mount point). To mount the file system on a Linux system, you need to use the mount command.

The common formats of the mount command are as follows:

mount [-l]

Simply using the mount command will display the device information that has been mounted in the system. Using the -l option will additionally display the volume. Tag name (readers can run it themselves and view the output results);

mount -a

-a option means to automatically check whether there are any omitted mounted device files in the /etc/fstab file. If If yes, the automatic mounting operation will be performed. Here is a brief introduction to the /etc/fstab file. This file is an automatically mounted file. When the system is powered on, it will actively read the contents of the /etc/fstab file. According to the configuration of the file, the system will automatically mount the specified device. The specific introduction to automatic mounting (modifying this file) will be explained in a subsequent article.

mount [-t 系統(tǒng)類(lèi)型] [-L 卷標(biāo)名] [-o 特殊選項(xiàng)] [-n] 設(shè)備文件名 掛載點(diǎn)

The meanings of each option are:

• -t System type: Specify the file system type to be mounted. Commonly supported types in Linux include EXT2, EXT3, EXT4, iso9660 (disc format), vfat, reiserfs, etc. If you do not specify a specific type, Linux will automatically detect it when mounting.

• -L Volume label name: In addition to using the device file name (such as /dev/hdc6), you can also use the volume label name of the file system for mounting.

• -n: By default, the system will write the actual mounting situation into the /etc/mtab file in real time, but in some scenarios (such as single-player maintenance mode ), in order to avoid problems, it will be deliberately not written. In this case, you need to use this option;

• -o Special options: You can specify additional options for mounting, such as read and write permissions , synchronous/asynchronous, etc., if not specified, the defaults are used. For specific special options, see Table 1;

【例 1】

[root@localhost ~]# mount
#查看系統(tǒng)中已經(jīng)掛載的文件系統(tǒng)，注意有虛擬文件系統(tǒng)
/dev/sda3 on / type ext4 (rw)  <--含義是，將 /dev/sda3 分區(qū)掛載到了 / 目錄上，文件系統(tǒng)是 ext4，具有讀寫(xiě)權(quán)限
proc on /proc type proc (rw)
sysfe on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw, gid=5, mode=620)
tmpfs on /dev/shm type tmpfs (rw)
/dev/sda1 on /boot type ext4 (rw)
none on /proc/sys/fe/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfe/rpc_pipefs type rpc_pipefs (rw)

【例 2】

修改特殊權(quán)限。通過(guò)例 1 我們查看到，/boot 分區(qū)已經(jīng)被掛載了，而且采用的是 defaults 選項(xiàng)。這里我們重新掛載分區(qū)，并采用 noexec 權(quán)限禁止執(zhí)行文件執(zhí)行，看看會(huì)出現(xiàn)什么情況（注意不要用 / 分區(qū)做實(shí)驗(yàn)，否則系統(tǒng)命令也就不能執(zhí)行了。

[root@localhost ~]# mount -o remount noexec /boot
#重新掛載 /boot 分區(qū)，并使用 noexec 權(quán)限
[root@localhost sh]# cd /boot
#寫(xiě)一個(gè) shell 腳本，看是否會(huì)運(yùn)行
[root@localhost boot]#vi hello.sh
#!/bin/bash
echo "hello!!"
[root@localhost boot]# chmod 755 hello.sh
[root@localhost boot]# ./hello.sh
-bash:./hello.sh:權(quán)限不夠
#雖然賦予了hello.sh執(zhí)行權(quán)限，但是仍然無(wú)法執(zhí)行
[root@localhost boot]# mount -o remount exec /boot
#記得改回來(lái)，否則會(huì)影響系統(tǒng)啟動(dòng)

對(duì)于特殊選項(xiàng)的修改，除非特殊場(chǎng)景下需要，否則不建議大家隨意修改，非常容易造成系統(tǒng)出現(xiàn)問(wèn)題，而且還找不到問(wèn)題的根源。

【例 3】掛載分區(qū)。

[root@localhost ~]# mkdir /mnt/disk1
#建立掛載點(diǎn)目錄
[root@localhost ~]# mount /dev/sdb1 /mnt/disk1
#掛載分區(qū)

/dev/sdb1 分區(qū)還沒(méi)有被劃分。我們?cè)谶@里只看看掛載分區(qū)的方式，非常簡(jiǎn)單，甚至不需要使用 "-ext4" 命令指定文件系統(tǒng)，因?yàn)橄到y(tǒng)可以自動(dòng)檢測(cè)。

可能會(huì)想，為什么使用 Linux 系統(tǒng)的硬盤(pán)分區(qū)這么麻煩，而不能像 Windows 系統(tǒng)那樣，硬盤(pán)安裝上就可以使用？

其實(shí)，硬盤(pán)分區(qū)（設(shè)備）掛載和卸載（使用 umount 命令）的概念源自 UNIX，UNIX 系統(tǒng)一般是作為服務(wù)器使用的，系統(tǒng)安全非常重要，特別是在網(wǎng)絡(luò)上，最簡(jiǎn)單有效的方法就是“不使用的硬盤(pán)分區(qū)（設(shè)備）不掛載”，因?yàn)闆](méi)有掛載的硬盤(pán)分區(qū)是無(wú)法訪問(wèn)的，這樣系統(tǒng)也就更安全了。

另外，這樣也可以減少掛載的硬盤(pán)分區(qū)數(shù)量，相應(yīng)地，也就可以減少系統(tǒng)維護(hù)文件的規(guī)模，當(dāng)然也就減少了系統(tǒng)的開(kāi)銷(xiāo)，即提高了系統(tǒng)的效率。

相關(guān)推薦：《Linux視頻教程》

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