1、fstab文件的作用
文件/etc/fstab存放的是系统中的文件系统信息。当正确的设置了该文件，则可以通过"mount /directory name"命令来加载一个文件系统，每种文件系统都对应一个独立的行，每行中的字段都有空格或tab键分开。同时fsck、 mount、umount的等命令都利用该程序。
2、下面是/etc/fatab文件的一个示例行： cat /proc/mounts
fs_spec fs_file fs_type fs_options fs_dump fs_pass
/dev/sda2 / ext4 defaults 1 1
/dev/sda1 /boot ext4 defaults 1 2
/dev/sda5 /home ext4 defaults 1 2
/dev/sda3 swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
fs_spec -
This field describes the block special device or remote filesystem to be mounted. For ordinary mounts it will hold (a link to) a block special device node (as created by mknod(8)) for the device to be mounted, like `/dev/cdrom‘ or `/dev/sdb7‘. For NFS mounts one will have <host>:<dir>, e.g., `knuth.aeb.nl:/‘. For procfs, use `proc‘. Instead of giving the device explicitly, one may indicate the filesystem that is to be mounted by its UUID or LABEL (cf. e2label(8) or xfs_admin(8)), writing LABEL=<label> or UUID=<uuid>, e.g., `LABEL=Boot‘ or `UUID=3e6be9de-8139-11d1‐ -9106-a43f08d823a6‘. It‘s also possible to use PARTUUID= and PARTLABEL=. These partitions identifiers are supported for example for GUID Partition Table (GPT). See mount(8), blkid(8) or lsblk(8) for more details about devices identifiers. Note that mount(8) uses UUIDs as strings. The string representation of the UUID should be based on lower case characters.
fs_file -
This field describes the mount point for the filesystem. For swap partitions, this field should be specified as `none‘. If the name of the mount point contains spaces these can be escaped as `\040‘
fs_type -
This field describes the type of the filesystem. Linux supports lots of filesystem types, the most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs. For more details, see mount(8). An entry swap denotes a file or partition to be used for swapping, cf. swapon(8). An entry none is useful for bind or move mounts. More than one type may be specified in a comma-separated list. mount(8) and umount(8) support filesystem subtypes. The subtype is defined by ‘.subtype‘ suffix. For example ‘fuse.sshfs‘. It‘s recommended to use subtype notation rather than add any prefix to the first fstab field (for example ‘sshfs#example.com‘ is deprecated).
查看系统支持的文件系统命令：ls /lib/modules/`uname -r`/kernel/fs/
fs_options -
This field describes the mount options associated with the filesystem. It is formatted as a comma separated list of options. It contains at least the type of mount plus any additional options appropriate to the filesystem type. For documentation on the available mount options, see mount(8). For documentation on the available swap options, see swapon(8).
- 推荐参数
noatime 关闭atime特性，提高性能，这是一个很老的特性，放心关闭，还能减少loadcycle
- 默认设置
defaults 使用默认设置。等于rw,suid,dev,exec,auto,nouser,async，具体含义看下面的解释。
- 自动与手动挂载
auto 在启动或在终端中输入mount -a时自动挂载 noauto 设备（分区）只能手动挂载 The file system can be mounted only explicitly.
- IO编码设置
iocharset＝ 在＝号后面加入你的本地编码，似乎在这个设备（分区）中做文件IO的时候就会自动做编 码的格式转换。 例如：你的某个分区是编码是utf8，而设备中文件的编码是gb2312，当是复制你设备中的文件到你的这 个分区时，它将自动做编码转换。 （不知道我的理解对不对，但是好像用下面的nls就可以实现转换。）
- 中文乱码的解决
nls= 在=号后面加入你的本地编码，你的中文就不会出现乱码。
- 读写权限
umask= 这是关于读写权限的，好像比下面的ro，rw选项更管用！！！ 例如：umask=000或0222，使得挂载时option中有default，普通用户仍然能读写挂载设备中的东西。 请大家补充！！！ ro 挂载为只读权限 rw 挂载为读写权限
- 可执行
exec 是一个默认设置项，它使在那个分区中的可执行的二进制文件能够执行。 noexec 二进制文件不允许执行。千万不要在你的root分区中用这个选项！！！
- I/O同步
sync 所有的I/O将以同步方式进行 async 所有的I/O将以非同步方式进行
- 用户挂载权限
user 允许任何用户挂载设备。 Implies noexec,nosuid,nodev unless overridden. nouser 只允许root用户挂载。这是默认设置。
suid Permit the operation of suid, and sgid bits. They are mostly used to allow users on a computer system to execute binary executables with temporarily elevated privileges in order to perform a specific task. nosuid Blocks the operation of suid, and sgid bits.
fs_dump -
This field is used for these filesystems by the dump(8) command to determine which filesystems need to be dumped. If the fifth field is not present, a value of zero is returned and dump will assume that the filesystem does not need to be dumped
fs_pass -
This field is used by the fsck(8) program to determine the order in which filesystem checks are done at reboot time. The root filesystem should be specified with a fs_passno of 1, and other filesystems should have a fs_passno of 2. Filesystems within a drive will be checked sequentially, but filesystems on different drives will be checked at the same time to utilize parallelism available in the hardware. If the sixth field is not present or zero, a value of zero is returned and fsck will assume that the filesystem does not need to be checked
时间： 2024-08-11 00:30:36