2_linux_ file and permission handling commands

Iii. Common commands for Linux

1. File Naming conventions

1) except/All characters are valid, the file name cannot contain/symbol

2) Some characters are best not used, such as spaces, tabs, backspace and characters @#$& ()

3) Avoid use. As the first character of a normal file, because. is the first character of a hidden file (must be mastered)

4) Case Sensitive

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2. Command format

Command format: command-option parameter???? Separated by a space

Example: ls-la/etc

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Description

1) When there are multiple options, it can be written together

2). Indicates the current directory,.. Represents the parent directory of the current directory

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3. Detailed instructions

Commands that the root user can execute

/sbin

/usr/sbin

All user-executable instructions

/bin

/usr/bin

Bin-binary???? Usr-user???????? Sbin-super binary

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3.1 File processing commands

1) LS

Drwxr-xr-x 2 root root 4096 12-01 20:52 bin

Linux
D: catalog file.
L: symbolic link ( point to another file , Similar to the shortcut under Windows )
S: socket file.
B: block device file , binary file.
C: character device file.
P: named pipe file.
-: ordinary file, or more precisely, not of the above several types of files. /span>

R-read read W-write write, x-execute execution

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Owner (creator) U???? Owning Group G???????? Other People O

User???????? Group???? Other

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2-Number of hard connections?

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Root root

Owner-owned group

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4096 size of file, approximate value

Block block default 512 bytes

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12-01 20:52

When the file was created or the last modified time value

Bin

Filename

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2) CD

3) PWD

4) Touch

5) mkdir

-P recursive creation of Mkdir-p Grandfather/father/son

6) CP

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7) MV, cut and rename

8) RM, only one file can be deleted

-F no need to ask

RmDir Delete Empty directory

9) Cat

Show first after the TAC command

More pagination Display file

One) head

tail)

) ln

Plus-S is a soft link

Do not add a hard link

Soft links are similar to Windows shortcuts

Can soft links cross file systems?

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Hardware link: cp-p (cp-p does not change the timestamp of the file) and real-time update, mapping, with the same inode as the original file

Hard links cannot cross file systems

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Ls–i

I-inode I node, file I node

The Linux kernel handles anything that requires a digital marker.

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3.2 Permission Handling commands

1) chmod

chmod u r

G W

o X

chmod u+wx chmod o-rx chmod g=rwx

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Note: RWX does not have the same meaning for files and directories

Example: To delete a file, instead of having W permission on a file, you should have W permission on the directory where the file resides.

2) Chown must have root authority

Chown Game:game/etc/service

Useradd gaomin

passwd gaomin

3) Umask

Run Umask

0022

0 Special Permission Bits

022 user rights bit, permission mask value

777

-022

=755

/*********************/

Linux permissions rule: Files created by default cannot grant X permissions

To change permissions for a file created by default 750, you should use a mask value of 027 (777-750), Umask 027

2_linux_ file and permission handling commands