Linux basic commands-Files and directories

Reference: "Bird's-brother Linux private Cuisine" The first seven chapters, 17/12/5 review

• File permissions

Rwx421;-r recursion; user, user group, other

Umask View default directory: 0002, that is, the other took off the W permission, can also be directly umask-s

Chgrp

Chown Zuo:zuo passwd

chmod +664 testfile//-rw-rw-r--

chmod U=RWX,GO=RW testfile

chmod +x testfile

+ number is add permission, no plus sign directly specify permissions

For the directory: R printable, W can modify any file in the directory, X can enter into a working directory

• Directory Configuration

FHS Standard

Third-party software generally in/USR/SRC or/opt

Kernel source code in/USR/SRC

/ Root

/bin -user binary files
In single-user mode, the common Linux commands you need to use are located in this directory. The commands used by all users of the system are set here.
For example: PS, ls, ping, grep, CP8

/sbin

It is usually used by system administrators to maintain the system. Example: Iptables, reboot, Fdisk, ifconfig, swapon commands

/ etc -configuration file

Hosts: The resolution of the device name (or domain name) to the IP address, equivalent to the local presence of DNS functionality.

/ Dev -device files
These include terminal equipment, USB or any device connected to the system. For example:/dev/tty1,/dev/usbmon0

/proc -Process information
This is a virtual file system that contains information about the processes that are running. For example: The/proc/{pid} directory contains information related to a specific PID.

/ var -variable file
This directory allows you to find files that may grow in content. Includes-System log files (/var/log), Package and database files (/var/lib), e-mail (/var/mail), print queue (/var/spool), lock file (/var/lock), and multiple restarts of required temporary files (/var/tmp);

/ tmp -temp file
Contains system and user-created temporary files. When the system restarts, the files in this directory will be deleted.

/ usr -unix software Resourse
Source code that contains binaries, library files, documents, and level two programs.
The/usr/bin contains a binary file of the user program. If you can't find the user binaries in/bin, go to the/usr/bin directory to see. For example: At, awk, CC, less, SCP.
The/usr/sbin contains the system administrator's binaries. If you can't find the system binaries in/sbin, go to the/usr/sbin directory to see it. For example: ATD, Cron, sshd, Useradd, Userdel.
The/usr/lib contains the libraries used by/usr/bin and/usr/sbin.
The user program installed from the source is included in the/usr/local. For example, when you install Apache from the source, it will be in/usr/local/apache2.

/home Directory
All users use the home directory to store their personal files.
For example:/home/john,/home/nikita

/ boot -boot loader files
The kernel's initrd, vmlinux, and grub files are located under/boot. Example: Initrd.img-2.6.32-24-generic

/lib -System Library
Contains library files that support binary files located under/bin and/sbin.
The library file is named LD or Lib. So.* for example: ld-2.11.1.so,libncurses.so.5.7

/opt -Optional add-on application
Contains additional applications from individual vendors.

/mnt -Mount Directory
A temporary installation directory where the system administrator can mount the file system.

/media -removable media devices
A temporary directory that is used to mount removable devices.
For example, the/media/cdrom,windows attached to the CD-ROM is also usually hung here

/srv -Service data
Contains data related to server-specific services.
For example,/srv/cvs contains CVS-related data.

• Directory Operations

Cd

Pwd

Mkdir:-p Recursive Creation-m Specify permissions

RmDir

Ls:-r list all files recursively;-s press from large to small;-t time from new to old;-R reverse

Cp:-p copy property;-r recursive copy;-d copy link file;-a equivalent to pdr;-u new copy;-L create hard link,-s soft link

RM-RF/

• File contents

Cat:-n line number;-a displays invisible characters

Tac

nl

More

Less: most commonly used

Head-n 10;-10 only print excluding the following 10 lines

Tail-n 10;-10 excluding the previous 10 lines

OD-A: Default read, C, D,o,x,ascii, decimal, octal, 16 binary

File View Files Type

• File time

Mtime content Changes

CTime state changes, such as permissions, properties

Atime file contents are read

Viewing time: ll--time=ctime filename; default is Mtime

Change time: touch-m/a Change the modification time, the access time is the current time

-D "2 days Ago"

-T specify time, [[CC]YY]MMDDHHMM[.SS]

• File Hidden Properties

Chattr + a filename, can only add content; +i, cannot be censored

Lsattr

• File Special Permissions

1. SetUID

-rwsr-xr-x 1 root root 27832 Jun 10 2014 /usr/bin/passwd

When s appears on the file owner's X-permission, called Suid

Valid only for binaries, performer requires x permission, temporary owner privilege

1. Set GID

When s appears on the user group's X-rights, called Sgid

Can be used for directory; the performer needs x permission; Temporary support for user groups

1. Sticky Bit

drwxrwxrwt 9 root root 4096 Dec 5 01:46 /tmp

When T appears on other X-rights

only for directories; only this user and root can delete the file

Chmod can be used to set the above three permissions, 421, the other capital S or T indicates that the user has no X permission, that is, empty

• Environment variables

Echo $PATH

Path= "$PATH":/opt/typora

• Find

1. which

Find execution files based on path

1. Whereis

Finding files in the database

1. Locate

updatedb updating database; fuzzy matching;-I ignoring case;-R regular matching

1. Find

Find | path| | option| |file|

• Time parameters

The day-mtime n,n days ago

-mtime +n,n days ago (n days not included)

Within-mtime-n,n days (including n days)

-newer file, newer than file

• User-related

-user Name

-group Name

-nouser

• Permission name related

-name filename

-size +/-100c;c for Bytes,k to kb,m for Mb,g GB

-type Type;type has the following types: F generic file, b/c device file, D directory, L link file, s socket, p pipeline

-perm mode; The file with the right mode;-mode superset, must all include a subset of Mode;+mode, including any mode

-exec plus other commandsfind /tmp -newer test1 -exec ls -l {} \;

Exercise: Build two accounts TMP1 and TMP2, support the same user group project, need to co-own the development rights of the/srv/ahome directory, and the directory does not allow other users to access

//Create users and user groups[Email protected]/]# Groupadd project [[email protected]/]# useradd-g project Tmp1[[email protected]/]# Useradd- G Project TMP2//Set up directory and Permissions[Email protected]/]# cd/srv [[email protected] srv]# mkdir./ahome[[email protected] srv]# chgrp project/srv/ahome[[ Email protected] srv]# chmod770Ahome[[email protected] srv]# ll-d ahomedrwxrwx---2Root Project4096Dec5  to: $Ahome//tmp1 Create file But TMP2 cannot access[[email protected] srv]# su tmp1[[email protected] srv]$ CD Ahome/[[email protected] ahome]$ Ls[[email protected] ahome]$ Touch Testfile[[email protected] ahome]$ su rootpassword: [[email protected] ahome]# su tmp2[[email protected] ahome]$ ll testfile-rw-rw-r--1TMP1 TMP10Dec5  to: -Testfile//Note TMP2 users are equivalent to other, only R permissions//Add Sugid permissions[email protected] ahome]$ su rootpassword: [[email protected] ahome]# chmod2770/srv/ahome//Verification[[email protected] ahome]# su tmp1[[email protected] ahome]$ touch File[[email protected] ahome]$ lltotal0-rw-rw-r--1TMP1 Project0Dec5  to: theFile//Note User groups become project[email protected] ahome]$ su rootpassword: [[email protected] ahome]# su tmp2[[email protected] ahome]$ ll Total0-rw-rw-r--1TMP1 Project0Dec5  to: theFile

Linux basic commands-Files and directories