Linux system learning

1 Historical Linux: LinuxIsNotUnixUnix: it is the predecessor of Linux. because of the charges, it can only be used by companies and schools. a good guy writes a Linux program after he finds himself very good at school. Linux core:

1. History

Linux: Linux Is Not Unix

Unix: it is the predecessor of Linux. because of the charges, it can only be used by companies and schools. a good guy writes a Linux program after he thinks it is very good at school.

Linux core: a kernel-based operating system. Linux brothers only write the kernel (hardware management program)

Linux releases: debian, slackware, suse, Hongqi, turbolinux, redhat, fedora, and mandrake (kernel-dependent tools). peripheral dependencies are written on the Linux kernel, many management hardware tools are written based on the dependency program.

Linux version: r. x. y, r: release version, x: even number, stable version, odd number, development version, y: number of bug fixes, e.g. 2.0.38

 

2 partitions:

VFS: Virtual File System. all file system interfaces can be programmed according to the interface (polymorphism)

Partition Table: records the partition information. generally, it is located at the beginning of the corresponding partition. a maximum of four records can be recorded. Therefore, a maximum of four extended partitions can be added to the primary partition (generally used to install the system ), the table below records logical partitions (different file systems)

Format: create different file systems, that is, different storage specifications for data.

Why Partition: you can mount a variety of file systems on the same hard disk, a variety of small cells, and different file systems have different small cells. Easier to manage

Windows: c :( primary partition), d :( extended partition/logical partition), e :( extended partition/logical partition)

Linux partition name: all devices are files in Linux, including character devices (such as keyboards) and block devices (such as hard disks)

--/Dev/xxyN,/dev/: directory name of all device files. xx: The first two letters of the partition name indicate the device type of the partition. Usually hd (IDE disk) or sd (SCSI disk ). Y: This letter indicates the device where the partition is located, which represents the hard disk number. N: indicates the partition. the first four partitions (primary and logical partitions) are from 1 to 4, and the logical partitions start from 5. For example:/dev/hda3: The third primary partition or logical partition on the first IDE hard disk,/dev/sdb6: The second logical partition on the second SCSI hard disk.

Access partition: mount is used to associate a partition to a directory. Mount partitions enable storage starting from the specified directory (called a mount point) to be used. For example: mount/dev/cdrom/mnt/cdr

At least two partitions:/partition, SWAP partition: when the hard disk is used as memory (virtual memory), the actual physical memory is twice

3. directory structure: google

4 boot sequence)

Load bios (hardware information)

Read MBR's config to find out the OS: find the operating system to start based on the MBR configuration.

Load the kernel of the OS: core file started by the operating system

Init process starts: init process started

Execute/etc/rc. d/sysinit: run the command

Start other modules (etc/modules. conf): read various modules of the system

Execute the run level scripts:, startup level, start to which level, layered structure, divided into six layers, each layer does not affect each other, can be modified (/etc/inittab)

Execute/etc/rc. d/rc. local: execute the script

Execute/bin/login

Shell started ..

5 linux help

Command -- help

Man command

6 command (commonly used)

Ls: list files and directories in the current directory. ls-l: displays details. ls-R: recursively displays all files in the directory and directories in the directory.

Tree: tree display

Cd: Enter the directory. cd .. the upper path is returned.

Pwd: current path

Mkdir: directory creation

Rmdir: delete an empty directory.

Rm-rf: recursively force delete a directory or file, force delete without jumping out of confirmation information

Touch: create a file

Cp: Copy, cp-r: recursive copy Directory

Mv: mobile, renamed

Vi: text editor (cross-platform, remote), vi file name (create or edit file)

Enter the command mode: only commands can be typed

A: append

Switch to command mode: esc

: W disk, q exited

More: View file content

Cat: View file content

Tac: View file content in reverse order

Head: View files, head-3: view the first three lines of files

Tail: View files; tail-3: list the last three rows

Clear: clear screen

Find: find the location of the file. find/-name my *

Grep (commonly used): name of the grep string file to find the line of the corresponding string in the text file

Whereis: View who executed the Command and its documentation

Echo: echo $ PATH: View PATH

Ln: link. the two files are synchronized, which is different from copy. Ln-s: soft link, equivalent to a windows Shortcut

Useradd: add a user and add the corresponding folder in/home. by default, the group is the same as the user name, and the group name is-g.

Usermod: modify user name,-g: modify group name

Userdel: delete a user

Su user name: Switch User

Passwd: specifies the user password.

More/etc/passwd: all users

More/etc/group: group information

Ls-l: displays detailed information (details ):

First: divided into-: file, l: link, d: Directory

Second to fourth: the owner of the file/directory and the permissions of the owner

Step 5 to Step 7: permission of the file/directory owner for others in the same group

Eighth to tenth: permissions of the remaining persons

Chmod: modify permissions, chmod u + x File name: modify permissions of the current user, chmod g + x File name: modify permissions of the same group, chmod 777: advanced operations, the first 7 indicates the user permission, the second 7 indicates the same group permission, and the third 7 indicates the remaining Member permission. the second 7 indicates the read and write operations (1 indicates the permission, 0 is none.) for example, 7: 111,5: 101.

Chown: modifies the owner and chown owner file name.

Wc: counts the number of lines, characters, and wordcount of a specified text file.

Col: filter control characters

Pipeline: Send the output of one command to another as the input of another command. Command 1 | Command 2 |... command n

Ls-Rl/etc | more

Cat/etc/passwd | wc

Cat/etc/passwd | grep lrj

Dmesg | grep eht0

Man bash | col-B> bash. txt

Ls-l | grep "^ d": list directories

Ls-l * | grep "^-" | wc-l: number of files in the current directory

Wall: wall 'command ', which sends the result of command execution to everyone logging on to the shell.

Command replacement: replace 'command' with the command

Redirection: write command output to a file or read the input command

Output: ls> cmd.txt, ls> cmd.txt,> represents replace,> represents append

Input: wall <aa.txt

Export: this command is required when the environment variable is set in linux to be used by others, such as: export PATH =/home/yyz/Applications/adt-bundle-linux-x86_64-20130917/sdk/tools: $ P
ATH

Ps: observe the following processes: ps-ef: all processes under the current user, ps-ef | grep process name

Kill: kill process, kill-9 process name, and force kill process

Service: service management, service name start: start the service. Service name stop: shut down service, commonly used: service iptables stop, firewall off

Wget URL: locally connect to the website (one of the functions), test

7. build a deployment environment

You must use command lines only because the server uses command lines only.

Service self-start: use of the chkconfig command (startup level and firewall settings (iptables ))