Linux Study Notes (permission issues)

Linux Study Notes (permission issues)-Linux general technology-Linux technology and application information, the following is a detailed description. [Root @ linux ~] # Cd/tmp
[Root @ linux tmp] # mkdir testing
[Root @ linux tmp] # chmod 744 testing
[Root @ linux tmp] # touch testing/testing
[Root @ linux tmp] # chmod 600 testing/testing
# The mkdir command is used to create a directory! Is the abbreviation of make directory.
# Use the root identity to create a directory named testing under/tmp,
# Change the permission of this directory to 744. The owner of this directory is root!
# In addition, touch can be used to create a file with no content. Therefore, touch testing/testing
# Create an empty/tmp/testing file!
[Root @ linux tmp] # ls-al
Drwxr -- r -- 2 root 4096 Jul 14 0:05 testing
# Let's take a closer look. The permission for the directory is 744, And the permissions for the group and user are root!
# Next, we will switch the root identity to a common identity user.
# Laruence's system has a general dmtsai user account, so it switches to dmtsai.
[Root @ linux tmp] # su dmtsai
# The su command is used to change the identity. We will introduce it in detail in the future.
# Note: In the bottom line, the user is found to have changed to dmtsai, and the prompt character is changed to $!
# That is to say, the operating system is now changed to dmtsai! So dmtsai
#/Tmp/testing is the permission of others. What can he do with/tmp/testing?
[Dmtsai @ linux tmp] $ ls-l testing <= the identity is dmtsai
Total 0
? ---------? ? ? ? ? Testing
# Check the information! Because dmtsai has the r permission, after all, the permissions are insufficient,
# Many materials are actually question marks (?) Come ~ Strange and tight ~
[Dmtsai @ linux tmp] $ cd testing <= at this time, the identity is dmtsai
Bash: cd: testing/: Permission denied
# Found? Even if we have the r permission, but do not have x, so
# Dmtsai cannot access/tmp/testing!
[Dmtsai @ linux tmp] $ exit
[Root @ linux tmp] # chown dmtsai testing
# Use exit to exit the su function. We set the owner of this testing directory
# Dmtsai: At this time, dmtsai becomes the owner, so what can this user do?
[Root @ linux tmp] # su dmtsai
[Dmtsai @ linux tmp] $ cd testing <= at this time, the identity is dmtsai
[Dmtsai @ linux testing] $ ls-l <= at this time, the identity is dmtsai
-Rw ------- 1 root 0 Jul 14 0:13 testing
# Switch your identity to dmtsai, and then you will be able to access testing! Check the content.
# Found the file testing! Only the root user can access the database ~
# Can I delete it?
[Dmtsai @ linux testing] $ rm testing <= at this time, the identity is dmtsai
Rm: remove write-protected regular empty file 'testing '? Y
# It can be deleted! Do you understand this?