Linux file directories and permissions

Linux file directories and permissions

Objective:

Linux generally divides the file-accessible identity into three categories, namely Owner/group/others, according to the permissions, each directory can have a relative identity-rwx[readable writable executable]

Users and Groups:

Owner: The file owner, such as Jane, who owns the file, can manipulate the file appropriately.

Group: A file has a group, such as a project group, with three people people1,people2, People3, and the file is owned by the project group, the three members within the group can manipulate the file appropriately.

Other: The other owner, that is, the executable operation of removing owner and group

Linux file properties

Use Ls-al to view the files in the current directory (-a shows hidden files, beginning with.)

Divided by Space: [Permissions] [link] [owner] [Group] [File size] [date modified] [filename]

1) [permissions]: consists of 10-bit characters representing the type and permissions of this file

The first character indicates that the file is a directory, a file, or a linked file, etc.

Directory

l When [d] is the directory, for example, the previous table file name is ". config" of the line;

l When [-] is the file, for example, the above table file is called "Esd_auth" the line;

L if [l] is a link file;

l if [b] is a device file inside the storage of the peripheral equipment (can be random access equipment);

l if [C] is indicated as a serial port device in the device file, such as a keyboard, mouse (one-time read device).

In the following characters, a group of three, each of which is a combination of three parameters, is "rwx".

l [R] stands for readable (read)

l [W] stands for writable (write)

l [x] stands for executable (execute).

The position of these three permissions will not change, if there is no permission, there will be a minus sign [-]

• Type and data can be separated when viewed: [-][rwx][r-x][r--]è1 234 567 890

1: Represents this file name as directory or file

234: Owner's permission

567: Same group User rights

2) [link]: Indicates how many file names are linked to this node (I-node)

Each file will log his permissions and attributes to the file system's I-node, and the directory tree we use is recorded using a file name, so each file name is linked to a i-node, and this property records how many different filenames are linked to the same i-node number.

3) [owner]: Represents the "Owner account" of this file (or directory)

4) [Group]: Indicates the group to which this file belongs

5) [File size]: The size of the file, the default unit is bytes

6) [Date Modified]: the date the file was created or the most recent modification date

7) [filename]: filename of file

Changing file properties and Permissions

1) chgrp: Changing the group of files (change group): The changed group name must be

exists within the/etc/group file, otherwise an error will be displayed.

2) Chown: Changing the file owner (change owner): The user must be an existing account in the system, that is, a record user name in the/etc/passwd file to change

Chown [-r] Account name file or directory

Chown [-r] Account name: Group name file or directory (with group to which the change file belongs)

-R: Continuous change of recursion (recursive), along with all files in the secondary directory

3) chmod: Change the file permissions, SUID, SGID, Sbit, and so on features

You can change permissions by using numbers or symbols, respectively.

Privilege Score Control: R:4 w:2 x:1

a) chmod [-r] XYZ file or directory

XYZ: The permission property of a numeric type, which is the sum of the numeric values of the Rwx property.

b) chmod | U g o A | + (Join)-(remove) = (set) | R W x | File or directory

User, group, others three kinds of identities, borrowed by U, G, O to generation. In addition, a represents all the identities

Linux file types and extensions

L Plain Text file (ASCII): Data that can be read directly, cat instructions can view the file

Binary file binary: An executable file for a general computer system

L Data Format file: A file in a specific format can be called a data file, last to view the file, and the use of cat will appear garbled

L Catalog (directory)

L linked file (link)

L Equipment and equipment files: Some files related to the perimeter and storage of the system, usually in the/dev directory

2 Block device files: Some storage data to provide system random access peripherals, such as hard disks and floppy disks [b]

2-character (character) device files: Peripheral devices for some serial ports, such as keyboards, mice, etc. [C]

L Data Interface file (sockets): Usually used for data transmission on the network

L Data Transfer file (FIFO, pipe): FIFO is also a special type of file, which solves the error problem caused by multiple programs accessing a file simultaneously.

Linux file extension

L. SH: script or batch file (scripts)

L Z, . Tar, . tar,.gz, . zip, *.tgz: Packaged compressed files, with different compression methods and different suffixes

L . html, . PHP: web-related files

Linux directory configuration based on-FHS (Filesystem Hierarchy Standard)

L FHS main functions: specification of what data should be placed in each specific directory

L FHS Four kinds of interactive forms under the catalogue

1) Shareable: A directory that can be shared with other system mounts

2) Non-shareable: some privacy data

3) Unchanging: Data that does not change frequently

4) Variable: constantly changing data

L FHS three-tier directory defined for the directory tree schema

1) Definition of three directories:

2)/(root, root directory): Related to the boot system;

3)/usr (Unix software Resource): Related to Software installation/execution;

4)/var (variable): related to the system operation process.

/etc----configuration file

/bin----Important Execution files

/dev----required device files

/lib----function Libraries required to execute the file and the modules needed by the kernel

/sbin----Important System execution files

Linux file directories and permissions