Linux setting command

1. Set system environment variables

In many cases, we need to set the system environment variables, such as when using JDK. by editing the bash. bashrc file, we can achieve this goal:
Back up and edit:
Sudo CP/etc/bash. bashrc/etc/bash. bashrc_backup
Sudo gedit/etc/bash. bashrc

Add the corresponding environment variables at the end of the file. These variables are valid for the entire system. For example, if my JDK is on the desktop, add the following line:
Java_home =/home/Aaron/desktop/jdk1.5
Export java_home
Path = $ path: $ java_home/bin
Export path

2. output the man manual page to a file
It is too painful to see man in the command line. We can output it to a file like this:
Man command | col-B> file.txt

3. Calculate the MD5 value of the file
Upload. MD5 to facilitate Viewing:
Md5sum file.txt> file.txt. MD5

4. Check the MD5 value of the file.
Verify that the file.txt and file.txt. MD5 files are in the same folder.
Enter
Md5sum-C file. ISO. MD5
You can.

5. Use "sudo" without a password (this is not secure)
This is very convenient, but it is not encouraged because it is not safe.
On the command line, enter:
Export editor = Vim &&
Sudo shortdo
Find
...
System_username all = (all) All
...
Replace
System_username all = (all) nopasswd: All
Save the file.

6. Killing the "sudo" Process
On the command line, enter:
Sudo-K
You can.