man /etc/fstab文件含义

man本身就是一个很好的书了！尽量用原有创作者的思路和语言去理解系统，不是吗？

通过man fstab可以大致知道

（fs_spec文件系统规格吧）设备

The first field, (fs_spec), describes the block special device or remote
filesystem（可以是SAN、FCoE、iSCSI） to be mounted.

（fs_file文件系统文件）挂载点

The second field, (fs_file), 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_vfstype文件系统类型,v不知道什么意思Virtual）

The third field, (fs_vfstype), describes the type of the filesystem. 
Linux supports lots of filesystem types, such as adfs, affs, autofs, coda,
coher-ent,  cramfs,  devpts,  efs, ext2, ext3, hfs, hpfs,
iso9660, jfs, minix, msdos, ncpfs, nfs, ntfs, proc, qnx4, reiserfs, romfs,
smbfs, sysv, tmpfs, udf,ufs, umsdos, vfat, xenix, xfs, and possibly others. For
more details, see mount(8).

(fs_mntops文件系统挂载选项，一般为default表示Use default
options: rw（可读写）, suid(针对所有用户和组), dev, exec（可执行）, auto（自动挂载）, nouser（只有超户）,
async, and relatime.)

The fourth field, (fs_mntops), 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 options for non-nfs
file systems, see mount(8).  For documentation on all nfs-specific options
have a look at nfs(5).   Common for all types of file system are the
options ''noauto'' (do not mount when "mount -a" is given, e.g., at boot time),
''user'' (allow auser to mount), and ''owner'' (allow device owner to mount),
and ''comment'' (e.g., for use by fstab-maintaining programs).  The
''owner''  and  ''com-ment'' options are Linux-specific.  For
more details, see mount(8).

这个默认（defaults）选项我是通过查看man fstab，然后发现所说第四列需要查看man mount（8），man
mount中有关于default的说明（括号8表示man的具体第八个手册）
（fs_freq文件系统频率？）关于dump的说明太多这里只理解到dump -
ext2/3/4 filesystem backup

The  fifth field, (fs_freq), 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.

（文件系统passno,passno什么意思？）fsck - check and repair a Linux file
system（检测和修复文件系统的）

The sixth field, (fs_passno), 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（根文件系统应该置为1）, and other filesystems should have a fs_passno of
2（其他系统应该置为2）.