Learning Log---linux punch 6

Review:

File management: LS, cat, TAC, tail, head, more, less, CP, MV, RM, touch, stat, file, nano

User management: Useradd, Usermod, Userdel, passwd, Groupadd, Groupmod, Groupdel, id, su, chage, Chfn, Chsh, Newgrp, gpasswd

User type:

Admin: 0

General Users: 1-65535

System users: 1-499,

The role of these users is that the system has just started to be used to start the processes of the system users, because the process is dependent on the user to create, indicating which resources can be accessed.

Ordinary users: the researcher

Userdd

-R: This is to create a system user,

Do not create home directories for users, start Bin/nologin, unable to log in users, so these system users are set for security period

Group Type:

Basic Group

Additional groups

Linux file types: All file types can be viewed using the document command

Normal file:-,f

Catalog: D

Link file: L (soft link)

Device files:

Character device (linear device): C

Block device (random device): b

Named pipes: P

Socket file: S

-D

-g-n

-L

Rights Management: Owner, group

File attributes have the concept of belonging to and belonging to the group:

Three types of users

Owner, group, other

File1:fedora, Fedora

Permissions: Divided into three types, read, write, execute

R, W, X

File:

R: You can use the Content view Class command to display its related content;

W: You can use the editor to modify its contents;

X: It is possible to initiate a process;

Catalog Files:

R: You can use the LS command to view the directory contents of the file information;

W: can create, delete files;

X: You can use the Ls-l command to view file information for the contents of the directory, and you can use the CD command to switch the directory to the working directory;

The user does not own a certain permission, then uses the-placeholder;

R-x:

r--

rw-

-rw-r--r--1 root root 852 Jul bincp.sh

:---, 0

001:--x, 1

010:-w-

011:-wx

100:r--

101:r-x

110:rw-, 6

111:RWX, 7

6:rw-

5:r-x

640:rw-r-----

With three-bit octal, you can represent three types of permissions.

Meta data, attributes, Inode:

An index node has an index node number, which stores the timestamp, permissions, owner, genus, size, and disk blocks of each file.

The user's permissions are put in the metadata of the file that exists.

Modify the owner, genus Group: admin only, Chown (change owner), CHGRP

Change file permissions: chmod

chmod command:

Permission to operate three types of users: using 8 binary form

chmod [-R] Octal-mode (octal) file ...

ACTION Specifies the permissions of the category User: Use U,g,o,a to assign weights, based on = or +/-

[Email protected] ~]# chmod u=rw,g=rw,o= [email protected]

[Email protected] ~]# chmod-r u+x g-x [email protected]

[[email protected] ~]# chmod +x [email protected] Execute permissions directly to the file plus all users

chmod Default does not modify the internal file permissions, need to add optional-R

U: Owner

G: Genus Group

O: Other

A: All

=: Operation permission of the specified category user; u=, ug=, u=,g=

+/-: Operation individual permissions for the specified category user: U-x, g+r, O-x, +x

Permissions to refer to other files are granted when a file is assigned

chmod--reference= file to modify permissions for the file to be referenced

rw-r--r--: rwxr-xr--

Common Permissions Models:

755:rwxr-xr-x

644:rw-r--r--

700:RWX------

600

750

640:rw-r-----

040

Umask: Each user has his or her own umask

Create file: 666-umask= octal permissions

The file default is never allowed to execute permissions;

Umask 023

666-023=644, if the last one appears is odd then +1 operation

Create directory: 777-umask

You can use umask+ numbers to modify the current user's umask

root:022

If the user name and the base group name are the same: 002; otherwise 022;

！！！！！！！！！！！！！！！！！！！！ Important!!!!!!!!!!!!!!!!!!!!!!!!

Modify the owner or genus of a file:

Chown, Chgrp here is the file.

-R: Recursive, so that the directory is changed

--reference=

chown [option] username[{:|.} GroupName] File ... Change the owner of the file

Chown Root:root/tmp/permfile can simultaneously modify a file's owner and owner group

Very important!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Permissions Application Model:

Note file: Drwxr-xr-x 2 root root 4096 Oct 7 12:40 2015-10-07-12-40

The current process is to run as the current user's identity;

The owner of the process is the same as the owner of the file, and if it is the same, the process accesses the file with the permission of the owner of the file;

The group to which the owner of a process belongs, whether one is the same as the genus of the file, or, if the same, the process accesses the file with the permissions of the filegroup;

The process accesses the file with the permission of the other user of the file;

Practice:

1. Create a new user OpenStack, but do not give it a home directory; After creation, use the SU command to switch to this user to view its command prompt and the values of the path and home environment variables;

# useradd-m OpenStack

# Su-openstack

# echo $PATH $HOME

2, copy/etc/skel directory for/home/openstack;

# Cp-r/etc/skel/home/openstack

3, change/home/openstack and its internal documents belong to the main group are openstack;

# Chown-r Openstack.openstack/home/openstack

4,/home/openstack and its internal files, belong to the group and other users do not have any access rights;

# chmod-r go=/home/openstack

# Su-openstack

# echo $PATH $HOME

Practice:

Complete the following tasks:

(1) New System group MySQL, new system user MySQL, belongs to MySQL group, requires that it has no home directory and shell for/sbin/nologin;

# groupadd-r MySQL

# useradd-r-s/sbin/nologin-g MySQL MySQL

(2) The new group of GID is 600 magedu; new user Gentoo, request their home directory for/users/gentoo, password and user name;

# groupadd-g Magedu

# mkdir/users must make sure it's there first

# useradd-d/users/gentoo Gentoo

# passwd Gentoo

(3) New user CentOS, whose home directory is/users/centos, password and user name;

# useradd-d/users/centos CentOS

# passwd CentOS

(4) New user www, whose home directory is/users/www; Delete www users, but keep their home directory;

# useradd-d/users/www www

# Userdel www

(5) User Gentoo and CentOS are magedu as their additional groups;

# usermod-a-G magedu Gentoo

# usermod-a-G magedu CentOS

Summary Rights Management: Chmod, Chown, Chgrp, umask

Bash Introduction:

Shell: human-computer interface

SH, csh, tcsh, bash, ksh, Dash, zsh

BASH: command interpreter, can explain what the instructions are, where to find the appropriate program, sent to the kernel

Bash feature SIX: Bash shortcut keys

CTRL + A: Jump to the beginning of the command

Ctrl+e: Tail

Ctrl+u: Deletes the contents of the command line from the beginning to the current cursor location

Ctrl+k: Delete the contents of the current cursor at the end of the command line

Ctrl+l: Clear screen, equivalent to clear command

CTRL + C: Cancel or terminate;

CTRL + Z: Send the current command to the background

Bash feature VII: Bash completion

Command completion:

Shell command: Internal, external

External: There is an executable program under a path in the system

which+ command to view the specific path of the command

Path, a colon-delimited set of paths that the directive defaults to to find the path of the executing program

command can be run with full path + instruction

Use the TAB key to perform a complete completion

Path completion: The completion of the given head path, or the current if there is no head path;

#,$

BASH: Interpreter, parser

Programming Languages:

C: Keywords, selection, order

Compiler: Language platform

Interpreter: Language platform

Program execution Logic:

Sequential execution

Select Execution (condition)

Cyclic execution: 1+...+100

Dynamic Language:

Apply for space at any time

Explanatory type

Perl, bash, Python

Static language:

Reasonable allocation of space in advance, high efficiency

Compiled type

C, C + +

Variable:

Data storage format:

Ascii:11 character encoding

Binary:11

Divide according to whether their variables need to be strictly defined by their type:

Strongly typed language: C requires the type of the variable to be pre-declared

Weakly typed language: Bash

Define the role of the variable type:

1, data storage format;

2, the effective storage range of data;

3, the comparison mechanism is different;

4. The type of operation involved is different;

Character type

Numeric type: positive, negative

Precise numerical type:

Integral type:

Approximate numerical type:

Floating point number

Single precision

Double precision

Boolean type:

Bash feature VIII: providing a programming environment

Variable

Program

#!/bin/bash the first line of the script file to tell the kernel which interpreter to use!!!!!! Which interpreter to use to interpret the script

Claims to be shebang

#！ is to tell the kernel that this is a program entry, and the subsequent kernel discovery is an interpreter, then it is considered not a simple executable program, it will invoke the interpreter to process the contents of the file

Each file has permission control, through the X this executable program flag, can determine whether the kernel processing

Add permission chmod +x file name

For example, LS is an instruction, is a binary program, to the kernel, the kernel to find the program's entry execution can

Exercise: Write a script

1, create a group newgroup, the ID number is 4000;

2, create a user mageedu1, ID number 3001, the additional group is newgroup;

3. Create Directory/TMP/HELLODIRXYZ

4, copy the/etc/fstab to the above directory

5. The owners and genera of the directories and internal documents are mageedu1;

6, let the directory and other users of internal documents do not have any permissions;

#!/bin/bash

# Description:

# Version:

# Datetime:

# Author:

mygroup= "Newgroup1"

Myuser= "MAGEEDU2"

Mydir= "/TMP/HELLODIRXYZ1"

myid=3002

Groupadd-g 4001 $myGroup

Useradd-u $myID-G $myGroup $myUser Note-u

mkdir $myDir

Cp/etc/fstab $myDir

Chown-r $myUser: $myUser $myDir Note-R

Chmod-r o= $myDir

unset mygroup myUser MyID MyDir

Learning Log---linux punch 6