Linux Learning Chapter II

After 10 days, learning the Linux system explaining course, during the period because there are other learning things to deal with, resulting in slower learning speed. The next learning time needs to be accelerated and devoted.

2-0 Single-user mode

Root password reset

Reboot----3 seconds to press a button to enter an interface----Select the second row, press e----Enter another interface, add a 1 at the end of the last line, and press ENTER----and then press b----to enter 1 mode successfully.

Instruction RunLevel View mode

Instruction passwd Change Password

Reboot restart after setting a new password

2-1 Rescue Mode

Another way to change the root password

2-2CD command

Cd=chang dir Change Directory

Instruction cd/tmp into the TMP directory

instruction PWD View current directory

Command CD back to the root directory

Instruction CD-Go back to the previous directory

Instruction CD ~=CD ^c =CD

CD. Go to the current directory

Cd.. Go to the previous level, equivalent to back

2-3ls command

Ls=list

View file or directory various information

Ls-i, Ls-li, Ls-a, ls-l, LS-T, etc.

2-4linux Environment variables

Alias aliases

Instruction alias s= ' ls-alt/var/' (after the alias input instruction s is equal to the input instruction ls ...) ) (current terminal is in effect)

Command alias to view the system and its own set of variable aliases

instruction which LS to view the absolute path of LS

The path directive uses

2-5 using the shortcut keys

Exit, logout, CTRL D quit terminal

Press CTRL u to clear all instructions being entered

Press CTRL k to clear the command after the cursor

Press CTRL C to break instructions in the run

Press CTRL Z to pause the process instruction FG recovery process

Press CTRL s screen to QUIESCE lock CTRL Q Recovery

Press CTRL L to clear the screen

3-1 Creating and deleting directories

instruction mkdir Creating a directory

Directive mkdir 234 created 234 directories on root/root/234/

instruction mkdir only one directory can be created at a time

Instruction man mkdir viewing the use of mkdir directives

Directive MKDIR-PV/TMP/1/2/3 creates 3 directories at a time under TMP

Directive rmdir Delete Directory can only delete empty directory

Instruction Rmdir-p 1/2/3 Delete 1, 2, 3 directories can only delete empty directories

3-2RM directive

Instruction RM Delete File

Directive RM-RFV or RM-FRV forcibly delete directories or files without prompting for error

3-3CP Copy command

Instruction cp-r Copy Directory

Instruction Df-h View system partition status

Command CP a B copy a to B

3-4 Moving and renaming MV

MV can either move files or move directories

Format MV A b move A to B or the directory A moving knife directory B

Command tree A view the branches under the A directory

3-5 File View Commands

Instruction Cat A view file a content

Command TAC A view file a content

Command more a press the ENTER key one line to view the file a in a single screen and one screen can not view

Instruction less A (IBID.), you can also use the arrow keys to view the line up and down, CTRL B or F can also, G or G can also,/a search keyword a,? A search keyword a

Command head A view file a top 10 lines

Instruction Head-2 A view only the first 2 lines

Instruction tail A view a last 10 lines

Instruction Tail-3 last 3 lines

3-6 File and Directory properties

Ls-l/A View the properties of a directory or file a

Ls-la a View a

3-7chmod command

File attribute Permissions rwx (111=7) readable writable executable

chmod changing permissions

Directive Chmod￥a Change the permissions of file A to ￥

Instruction chmod-r￥111 111 permissions for all files and subdirectories changed to ￥

Umask

3-8chown command

Directive Chown A b.txt change the genus Group of B.txt

Useradd a CREATE User A

Groupadd c Create user Group C

Directive Chown:c B.txt Change the owning group of B.txt

Directive Chown Root:root B.txt to change the group of B.txt and its owning group to root

Historical command History! Add character or number to recall

Chown-r Modify the directory under all

3-9chattr File Hidden Properties

Lsattr View current directory Special properties Lsattr-r list all lsattr-d view only the directory itself

Chattr +a 1.txt Adds a privilege to 1.txt

echo "QQ" >1.txt 1.txt empty and then write to QQ

echo "QQ" >>1.txt QQ written to 1.txt last line

Chattr-a Subtract a permission

Chattr +i Permissions

Touch 1/2.txt Create 2.txt in 1 directory

4-0 Suid of special permission

Set_uid

/etc/shadow

/usr/bin/passwd

chmod u+s/tmp/ls gives LS u+s permission S is suid or set UID

Su-, logout temporary user Switching and return. #与 $

4-1 Special Permissions Sgid

Set_gid

R=4, w=2, X=1, set_uid=4, set_gid=2, stick_bit=1

4-2 Sticky of special permission

Stick_bit

prevent others from deleting their own files (between different users)

: wq! Force Save exit

Root mode run chmod o+t join T permissions other users cannot delete

4-3find Search should

Which, Whereis, locate can search the file path, but there are certain limitations, search scope and permissions, etc.

UpdateDB Refreshing the database

Directive find/tmp/-name ' ab ' found in the TMP directory AB file (single quote is not added)

Directive find/tmp/-name "A *" to find files beginning with a (double quotation marks can be used without a single quotation mark)

Instruction find/tmp/-type D Find all directories F Find all Files

find/tmp/-mtime-10 Find files within 10 days +10 found 10 days ago (created or modified)-mmin units are minutes

find/tmp/-type F |xargs rm find all files under TMP and delete RM can be changed to other instructions with

4-4 Three Time Properties

Mtime, Atime, CTime

Date Check datetime

Atime Access Time

Mtime Create or change a time

CTime changing the original data time

Command stat A view the properties of a file

Touch a If a does not exist create a new file A, if the file exists, changes the file 3 time

M to C must be changed, C change m not necessarily changed for example, change permissions

4-5 Soft links and hard links

Soft link = Shortcut

Directive Ln-s/root/12.txt/tmp/23.txt creates a soft link in root file 12.txt under TMP called 23.txt Create a soft link with an absolute path to avoid confusion

can also do the directory of Soft link 12.txt to the directory name

Inode: Metadata record data for each file or directory core important information an inode corresponds to one or more files in turn.

Ls-i/root/a View the inode of file a

DU-SH/ROOT/A viewing the size of file a

Hard links allow multiple files to be shared with one inode at a time

Directive ln/root/a/tmp/b Let the resulting B become a avatar hard link

Hard links cannot boast partitions and cannot do directory hard links under each partition a set of separate inode partitions under a 123 partition B there are also 123

4-6 User name File

User and Group Management

CAT/ETC/PASSWD (Core configuration file)

By: Divided into 7 segments

First paragraph user name

Second paragraph password

Third Segment UID View user uid by ID command such as ID root

Fourth Group ID

The fifth paragraph explains that the normal user is empty

Sixth paragraph home directory ordinary user is/home/user name:

Seventh Shell General/bin/bash can log in also have/sbin/nologin non-login/bin/false not login

4-7 Password file

/etc/shadow Store Password

By: Divided into 9 segments

1. User Name

2. User encrypted password

3, from 1970.1.1 to the last time to change the password

4. How many days before the password can be modified

5. How long does the password expire?

6, the password expires a few days before the warning

7. How many days to delay after the password expires lock account

8. Account Life cycle

9, retention value, no use

4-8 Adding and removing user groups

Directive Groupadd a creates group A

instruction Tail/etc/group Viewing the information for a group

Instruction/etc/gshadow View the password for the group

The ID of Group B created by Groupadd-g 555 B is 555. Normal create group ID starting from 500, the ID of the group created after creating B starts with 556

Directive Groupdel A Delete Group A group is used to summarize the user group inside if there are users this group cannot be deleted. Additional groups can be deleted, basic groups can not

4-9 Adding and removing users

Directive Useradd A creates both group A and user A

Directive Useradd-u 505-g A B creates a User B uid of 505 added to the instruction in Group A can also be changed to a GID

Instruction useradd-d Specify user home directory-s Specify user shell

Useradd-m-S does not create a home directory when creating a user

Directive Userdel a deletes user A but does not delete home directories

Directive Userdel-r a deletes a home directory when user A is deleted

5-0usermod Modifying user Properties

Instruction Usermod-g 501 A user A's GID changed to 501

Useradd-g Increase user Expansion Group expansion group can be deleted

Usermod-u-g-g-d-s can be changed with

Usermod-l lock A user cannot login-u unlock

5-1password Change Password

Instruction passwd more root password

Directive passwd A change the password for user A

Instruction mkpasswd prompt does not exist to enter instructions for Yum install-y expect install expect package again enter MKPASSWD run.

Mkpasswd-l specified password length-s number of symbols----Specify number of digits-C Specify the number of primary letters C

Instruction passwd--stdin A set User A's password

Command echo "B" |passed--stdin a set User A's password to B

5-2SU Switching users

The instruction ID or whoami can be checked by the current user

Instruction Su-b switch to B user

Instruction Su-C "instruction B" a executes instruction B under a user

5-3sudo detailed

sudo root gives ordinary users the command to root without a password

More difficult to use

5-4DF command

Instruction DF View system per partition usage cannot view swap

instruction free to view swap usage

Df-h,-K,-m display sizes in different units

instruction Df-i viewing partition inode usage

5-5du command

Du view file, directory usage size unit k

Du-h,-M,-K display in different units

du-sh/a/View the size of a file or directory A (size, DU-SB, and ls-lb to see the true size)

5-6fdisk command

Instruction fdisk-l View disk condition

Instruction Fdisk/dev/sdb enters b disk (instruction parted handles disks larger than 2T) enter M to view the commands that can be manipulated and then enter N to increase the partition E for the extended partition p as the primary partition L is the logical partition (subdivision under the extended partition) Example: p-1-1-+2g (size): W Deposit exit

5-7 Disk Format MKE2FS

The disk partition must be formatted before it can be used

Cat/etc/filesystems Viewing file system formats

iso9960 disc format, Common ext2, ext3, Ext4

Directive MKFS. viewing formatting formats

Instruction MKFS.EXT4/DEV/SDB5 Format the disk SDB5 in EXT4 format

Instruction Mke2fs-t ext4-b 2048-m 1-l A/DEV/SDB1 partition 1 formatted as EXT4 format, block size 2048, reserved 1%, label a

5-8 Disk mount and Uninstall

The disk must be mounted after it is formatted to write data

Directive mount/dev/sdb5/mnt/to mount the partition 5 under the MNT

Instruction Df-t or-M view all partition formats, mount points, and more

Umount-l/DEV/SDB5 unloading SDB5 mount point

5-9 Partition Table Fstab

Set up auto mount on boot

Instruction Cat/etc/fstab then add a partition setting

or instruction Vi/etc/rc.local then add an instruction

Blkid

Mount-a

Mount-o

Linux Learning Chapter II