硬链接和软链接的区别与作用

软链接(符号链接)：

1、可以在不同的文件系统中进行，相当于快捷方式

2、删除源文件后，快捷方式将不能链接到源文件

[[email protected] ~]# cd /tmp

[[email protected] tmp]# du -sb;df -i    #du -sb是计算整个/tmp目录下有多少 bytes的容量

5329.

[[email protected] tmp]# cd

[[email protected] ~]# touch rlj

[[email protected] ~]# ln -s /root/rlj /tmp/rlj.lnk

[[email protected] ~]# cd /tmp

[[email protected] tmp]# du -sb;df -i    #软链接会占用inode数

5338.

[[email protected] tmp]# ll /root/rlj ./rlj.lnk

lrwxrwxrwx. 1 root root 9 Oct  6 16:37 ./rlj.lnk -> /root/rlj

-rw-r--r--. 1 root root 0 Oct  6 16:37 /root/rlj

[[email protected] tmp]# cd

[[email protected] ~]# ln -s rlj /etc/rlj.lnk  #此处rlj应该跟绝对路径，否则链接的文件将出现闪烁的状态

[[email protected] ~]# ll rlj /etc/rlj.lnk

lrwxrwxrwx. 1 root root 3 Oct  6 16:40 /etc/rlj.lnk -> rlj

-rw-r--r--. 1 root root 0 Oct  6 16:37 rlj

[[email protected] ~]# echo "this is a rlj file" >> rlj

[[email protected] ~]# cat rlj

this is a rlj file

[[email protected] ~]# rm -f rlj

[[email protected] ~]# ll rlj

ls: cannot access rlj: No such file or directory

[[email protected] ~]# vim /tmp/rlj.lnk       #可看出源档案被删除后又重新建立了此档案

~

~

"rlj.lnk" [New File]

[[email protected] ~]# mkdir rlj

[[email protected] ~]# ln -s /root/rlj /var/   #为目录建立软链接

[[email protected] ~]# ll /var/rlj

lrwxrwxrwx. 1 root root 9 Oct  6 16:43 /var/rlj -> /root/rlj

[[email protected] ~]# rm -fr rlj

[[email protected] ~]# ll /var/rlj

lrwxrwxrwx. 1 root root 9 Oct  6 16:43 /var/rlj -> /root/rlj

硬链接：

1、不能对目录进行硬件链接

2、不能跨越不同的文件系统

[[email protected] ~]# touch ylj

[[email protected] ~]# vim ylj

[[email protected] ~]# ln ylj /tmp

[[email protected] ~]# ln ylj /

[[email protected] ~]# cd /tmp

[[email protected] tmp]# ll -hi ylj /root/ylj /ylj  #以人类可读性方式显示并给出连接的档案数，还可以看出它们的inode数相同均为204670563

204670563 -rw-r--r--. 3 root root 19 Oct  6 15:55 /root/ylj

204670563 -rw-r--r--. 3 root root 19 Oct  6 15:55 ylj

204670563 -rw-r--r--. 3 root root 19 Oct  6 15:55 /ylj

[[email protected] tmp]# vim ylj

[[email protected] tmp]# cat /root/ylj

this is a ylj file

ylj don‘t support directory.

[[email protected] tmp]# cat /ylj

this is a ylj file

ylj don‘t support directory.

[[email protected] tmp]# rm -f ylj

[[email protected] tmp]# ll -hi /ylj /root/ylj

204670563 -rw-r--r--. 2 root root 48 Oct  6 15:57 /root/ylj

204670563 -rw-r--r--. 2 root root 48 Oct  6 15:57 /ylj

[[email protected] tmp]# mkdir yl

[[email protected] tmp]# ln yl /     #硬链接对目录不生效

ln: ‘yl’: hard link not allowed for directory