(i) Common Linux commands

I.. chmod modify FILE Permissions

Each file or directory has three groups of access rights, each group is represented by three bits, respectively, the read, write, and execute permissions of the file owner, the read, write, and execute permissions of the user belonging to the primary group, and the read, write, and execute permissions of other users in the system. The horizontal line represents an empty license. R stands for read-only, W stands for write, and x stands for executable. Note there are 10 locations. The first character specifies the file type. In the usual sense, a directory is also a file. If the first character is a horizontal line, it represents a non-directory file. If it is D, the representation is a directory.

After determining the access rights of a file, users can use the chmod command provided by the Linux system to reset different access rights. You can also use the Chown command to change the owner of a file or directory. Use the CHGRP command to change the user group for a file or directory.

User groups include:
U means "user", which is the owner of the file or directory.
G means "same group user", that is, all users who have the same group ID as the file owner.
O means "other (others) users".
A means "all users". It is the system default value

The operation symbols can be:
+ Add a permission.
-Cancels a permission.
= gives the given permission and cancels all other permissions, if any.

Permissions can be any combination of the following letters:
R is readable.
W writable.
X executable

The meaning of the attribute represented by the number: 0 means no permissions, 1 means executable permission, 2 is writable, 4 is read, and then it is added. So the format of the numeric attribute should be 3 octal numbers from 0 to 7, in the Order of (U) (g) (O).

second, Linux shutdown, restartRestart: Reboot shutdown: 1, halt immediately shut down 2, Poweroff immediately shut down the Machine 3, Shutdown-h now immediately shutdown (root user) 4, shutdown-h 10 10 minutes after the shutdown Shutdown command is the most secure to shut down the system. three, Vmvare set Ubuntu boot to the command line open1, command: sudo gedit/etc/default/gru2, b find this line grub_cmdline_linux_default= "quiet splash" changed to grub_cmdline_linux_default= " Quiet Splash Text3, "in the input command: sudo update-gru4, enter the reboot command to restart the system 5, boot automatically into the tty1 command line interface

(i) Common Linux commands