Shulou(Shulou.com)06/02 Report--

1Difference between su su and Jol -.

After switching users, su is still under the current user's home directory, but not the switched user's home directory.

Su-after switching users, the current user environment variables are changed under the user's home directory. So switch users with su-command

2Jing sudo commands users to delegate power to ordinary users with root users.

Either visudo or / etc/sudoers can edit the file to delegate power to the corresponding users. It is recommended to use the visudo command to verify whether the command is miswritten.

Root ALL= (ALL) ALL

Root: for users who can use the sudo command

ALL: for hosts that can use sudo

(ALL): to execute commands in what capacity after using sudo can also be written as (root)

ALL: indicates which commands the user is allowed to run (command full path representation)

Sudo-l View the configuration commands in the sudo file

When ordinary users need most of the permissions, a small number of them can be used when they don't want them. Give it power instead of taking it.

3, permission settings of the file

File permissions

Rwx read and write execution

R-4

WMULMUPUR 2

X-1

U represents the owner

G represents all groups

O for other people

Modify file permissions method

Chmod 755 filename

Chmod ugo+x file name

4, directory permissions

Rwx read and write execution

R 4 can I view the contents of the directory ls

Can W2 be created, deleted or renamed under the directory

Does x 1 have permission to enter the directory cd

Modify directory permissions method

Chmod 755 directory name

Chmod ugo+x directory name

5The permissions of most files and directories in the Linux system are set to 644 and 755.

The maximum permission given by the file is 666

The maximum permission given by the directory is 777

Because the umask value set in the system is 0022

Umask modification / etc/profile

6. How to view and modify the permissions of file hidden attributes

View hidden file properties lsattr file name

Modify file hidden permissions

Chattr

A cannot be modified or deleted

I cannot be modified or deleted

Chattr + a

Chattr + I

Chattr-a

Chattr-I

7Med MD5 encryption

Encrypt a file to generate a fingerprint file. When the source file is modified, verify the encrypted file. It is often used in scheduled tasks.

Command:

Md5sum passwd generates encrypted fingerprint serial number

Md5sum passwd > passwd.txt inputs the encrypted fingerprint into the passwd.txt file

Md5sum-c passwd.txt verifies the fingerprint file. When the source file is modified, the verification will report an error.

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