One, hard links
Number of links is the number of names:
ln (link) hard links, multiple identical inode files (same partition), multiple hard-link files exist on the hard disk only occupy one file capacity.
The hard links created are equal, the inode is the same, the deletion of one is not affected, and the other files can still be used.
The nature of hard links: Create multiple names for a file.
Create multiple hard links to see how the number of links changes (+1), the number of links is a few file names.
In the same partition, the same inode number must be a file.
The original file
[Email protected] testdir]# ll-iman.txt15-rw-r--r--. 1 root root 15978 8 2008man.txt
Create first hard link
[Email protected] testdir]# lnman.txt test/f11[[email protected] testdir]# ll-iman.txt test/f11 15-rw-r--r--. 2 root root15978 8 man.txt15-rw-r--r--. 2 Root root15978 8 test/f11
Create a second hard link
[Email protected] testdir]# lnman.txt testdir/f22[[email protected] testdir]# ll-iman.txt testdir/f22 test/f11 15-rw-r- -R--. 3 root root15978 8 man.txt15-rw-r--r--. 3 root root15978 8 testdir/f2215-rw-r--r--. 3 Root root15978 8 test/f11
When you create multiple hard links to a file, all files have the same inode, permissions, size, and time attributes.
[Email protected] testdir]# echo "AAAAAAAAAAAAAAAAAAA" >man.txt[[email protected] testdir]# ll-itestdir/f22 test/ F11 Man.txt Test/f15-rw-r--r--. 4 root root 8Jul 09:49 man.txt15-rw-r--r--. 4 root root 8Jul 09:49 testdir/f2215-rw-r--r--. 4 root root 8Jul 09:49 test/f15-rw-r--r--. 4 root root 8Jul 09:49 test/f11
When writing data to a file, the properties of other files are changed as well.
[[email protected] testdir]# lnman.txt/roo/aln:creating hard link '/roo/a ' = ' man.txt ': No such file or directory
Hard links cannot be created across partitions, across devices
[Email protected] testdir]# lnhelp/hln: ' help/': Hard link notallowed for directory
Hard links cannot be for directories
[[Email protected] testdir]# ll -iman.txt man131 -rw-r--r--. 6 root root3256 aug 1 16:54 man131 -rw-r--r--. 6 root root3256 aug 1 16:54 man.txt[[email protected] testdir]# rm -fman.txt [[email protected] testdir]# tailman -Z, --ditroff use groff and force it to produceditroff -?, --help give this help list --usage give a short usage message -V, --version print program version Mandatory or Optionalarguments to long options are also mandatory or optionalfor any corresponding shortoptions. report bugs [email protected]
When the original file is deleted, the linked file can still be viewed
Second, soft (soft) Link:
Soft links are equivalent to Windows shortcuts
[Email protected] testdir]# ln-sman.txt man[[email protected] testdir]# ls-li man.txt man12 lrwxrwxrwx. 1 root root 7Jul 10:04 man--Man.txt15-rw-r--r--. 4 root root 8Jul 09:49 man.txt
Create a soft link file, the link file will be identified in green font and point to the original file, through observation can find two files of different inode number
Create a soft link file for the original file
[[email protected] testdir]# ln –sman.txt /roo/ man.txt[[email protected] testdir]# ll/root/man.txtlrwxrwxrwx. 1 root root 7 Aug 1 16:55 /root/man.txt ->man.txt[[email protected] Testdir]# ln –s. /.. /testdir/man.txt /root/man1[[email protected] testdir]# ll/root/man1lrwxrwxrwx. 1  ROOT ROOT  9 AUG 1 16:56 /ROOT/MAN1 ->&NBSP, .... /.. /testdir/man.txt [[email protected] testdir]# ln -s/testdir/ /root/test1[[email protected] testdir]# ll -d/testdir/ /root/test1lrwxrwxrwx. 1 root Root 9 aug 1 17:02 /root/test1 -> /testdir/drwxr-xr-x. 3 root root 34aug 1 16:53 /testdir/
Through the above example can be found that soft links can be created for the directory, cross-partition, and the creation of the time to pay attention to the problem of the path, if the path is wrong, the link file will save the displayed
Soft links need to be aware of absolute and relative paths relative to the path of a soft link rather than the path of the current directory (pointing to the location relative to the current working directory or directory)
[[email protected] testdir]# ln -s/testdir/man /root/111111[[email protected] testdir]# ll -i/testdir/man /root/111111105103873 lrwxrwxrwx. 1 rootroot 12 aug 1 17:16 /root/111111 -> /testdir/man 131 -rw-r--r--. 5 root root 3256 aug 1 16:54 /testdir/man[[email protected] testdir]# rm -f/testdir/man [[email protected] testdir]# ll/testdir/man /root/111111 Ls: cannot access/testdir/man: no such file or directorylrwxrwxrwx. 1 root root 12Aug 1 17:16 /root/111111 ->/testdir/man[[email Protected] testdir]# cat/root/111111 cat: /root/111111: no suchfile or directory
When the original file is deleted, the created soft link file will not be accessible
Third, the difference between soft and hard links:
The difference between a soft link and a hard link is that the soft link is invalidated after the original file is deleted, but the hard link is still available, and the soft link works for the file or directory, but the hard link is only available for the file, not a hard link to the directory, and the soft link and the original file can be in different file systems. However, the hard link must be within the same file system as the original file (such as a Linux partition).
This article is from the "Linux on the Road" blog, be sure to keep this source http://dreamlinuxc.blog.51cto.com/5733156/1833082
Linux hard links, the creation of soft links, and the difference between the two