Linux — 硬链接与符号链接

硬链接时，新增加一个 inode 链接到文件的数据块；而符号链接时，只是新创建了一个文件，它指向所链接的文件。

 

# 1. 使用文件 /oradata2/yct/rc.local 进行测试

[oracle@sbdatabase yct]$ pwd
/oradata2/yct
[oracle@sbdatabase yct]$ ll
total 4
-rwxr-xr-x 1 oracle dba 220 Dec  9 16:30 rc.local
[oracle@sbdatabase yct]$ more rc.local
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.

 

touch /var/lock/subsys/local

 

# 2. 进行硬链接，inode 数增加
[oracle@sbdatabase yct]$ ln rc.local rc.local_hard.ln
[oracle@sbdatabase yct]$ ll
total 8
-rwxr-xr-x 2 oracle dba 220 Dec  9 16:30 rc.local
-rwxr-xr-x 2 oracle dba 220 Dec  9 16:30 rc.local_hard.ln

 

# 3. 进行符号链接，inode数并没有增加
[oracle@sbdatabase yct]$ ln -s rc.local rc.local_soft.ln
[oracle@sbdatabase yct]$ ll
total 8
-rwxr-xr-x 2 oracle dba 220 Dec  9 16:30 rc.local
-rwxr-xr-x 2 oracle dba 220 Dec  9 16:30 rc.local_hard.ln
lrwxrwxrwx 1 oracle dba   8 Dec  9 17:03 rc.local_soft.ln -> rc.local

 

# 4. 删除原文件后，硬链接仍可用，而符号链接失效。
[oracle@sbdatabase yct]$ rm rc.local
[oracle@sbdatabase yct]$ ll
total 4
-rwxr-xr-x 1 oracle dba 220 Dec  9 16:30 rc.local_hard.ln
lrwxrwxrwx 1 oracle dba   8 Dec  9 17:03 rc.local_soft.ln -> rc.local
[oracle@sbdatabase yct]$ more rc.local_hard.ln
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.

 

touch /var/lock/subsys/local
[oracle@sbdatabase yct]$ more rc.local_soft.ln
rc.local_soft.ln: No such file or directory

 

# 5. 硬链接不能链接目录

[oracle@sbdatabase yct]$ rm -r *
[oracle@sbdatabase yct]$ ll
total 0
[oracle@sbdatabase yct]$ mkdir t1
[oracle@sbdatabase yct]$ ln t1 t1_hard.ln
ln: `t1': hard link not allowed for directory
[oracle@sbdatabase yct]$ ln -s t1 t1_soft.ln
[oracle@sbdatabase yct]$ ll
total 4
drwxr-xr-x 2 oracle dba 4096 Dec  9 17:09 t1
lrwxrwxrwx 1 oracle dba    2 Dec  9 17:09 t1_soft.ln -> t1
[oracle@sbdatabase yct]$