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Linux 命令集合

Posted by Kylin Soong on Mar 17, 2016 categorized as linux

Local and Remote Logins

The ways of quiting shell Session:

  • exit command
  • pressing Ctrl+d

Using SSH Key-based Authentication

  • Create an SSH key pair in local server
$ ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/home/kylin/.ssh/id_rsa): /home/kylin/.ssh/id_t_rsa                  
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/kylin/.ssh/id_t_rsa.
Your public key has been saved in /home/kylin/.ssh/id_t_rsa.pub.
...
  • Send the SSH public key to the remote server
[kylin@ksoong ~]$ ssh-copy-id -i ~/.ssh/id_t_rsa.pub root@10.66.218.46
/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@10.66.218.46's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'root@10.66.218.46'"
and check to make sure that only the key(s) you wanted were added.
  • Login into remote server
$ ssh root@10.66.218.46

Creating and Viewing an SoS Report

  • If currently working as a non-root user, switch to root.
$ su -
Password:
  • Run the sosreport command. This may take many minutes on larger systems.
# sosreport
  • Change directory to /var/tmp, and unpack the archive.
# cd /var/tmp
# tar -xvJf sosreport-*.tar.xz
  • Change directory to the resulting subdirectory and browse the files found there.
# cd sosreport-ksoong-20160306161748

File System Navigation

Linux File System

Linux File System DESC

Command-Line File Management

  • Create Files
$ touch song1.mp3 song2.mp3 song3.mp3 song4.mp3 song5.mp3
$ touch snap1.jpg snap2.jpg snap3.jpg snap4.jpg snap5.jpg
$ touch film1.avi film2.avi film3.avi film4.avi film5.avi
$ ls -l
  • Move Files
$ mv song1.mp3 song2.mp3 song3.mp3 song4.mp3 song5.mp3 Music/
$ mv snap1.jpg snap2.jpg snap3.jpg snap4.jpg snap5.jpg Pictures/
$ mv film1.avi film2.avi film3.avi film4.avi film5.avi Videos/
$ ls -l Music/ Videos/ Pictures/
  • Create Directories
$ mkdir friends family work
$ rmdir friends family work

This Section will demonstrate how to use hard links and soft links to make multiple names point to the same file.

  1. The command ln creates new hard links to existing files. The command expects an existing file as the first argument, followed by one or more additional hard links.
  2. The ln -s command creates a soft link, which is also called a “symbolic link”. A soft link is not a regular file, but a special type of file that points to an existing file or directory. Unlike hard links, soft links can point to a directory, and the target to which a soft link points can be on a different file system.
  • Create an additional hard link
# ln /usr/share/doc/qemu/qmp-commands.txt /root/qmp-commands.txt
  • Verify the link count on the newly created link
# ls -l /root/qmp-commands.txt 
-rw-r--r--. 2 root root 65630 Nov 18  2013 /root/qmp-commands.txt
  • Verify the link count on the original file
# ls -l /usr/share/doc/qemu/qmp-commands.txt 
-rw-r--r--. 2 root root 65630 Nov 18  2013 /usr/share/doc/qemu/qmp-commands.txt
  • Create the soft link
# ln -s /tmp/ /root/tmpdir
  • Verify the newly created link with
# ls -l
lrwxrwxrwx. 1 root root     5 Mar  6 16:06 tmpdir -> /tmp/
# cd tmpdir/
# ls -lR

Users and Groups

  1. /etc/passwd - store information about local users
  2. /etc/group - store information about local groups

Useful Commands:

$ id
$ ps au
  • The id command is used to show information about the current logged-in user.
  • The ps command is used to view process information. Add the a option to view all processes with a terminal. To view the user associated with a process, include the u option.

Running Commands as root

  • View the user and group information and display the current working directory.
$ id
uid=1000(kylin) gid=1000(kylin) groups=1000(kylin),987(docker) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
$ pwd
/home/kylin
  • View the variables which specify the home directory and the locations searched for executable files.
$ echo $HOME
/home/kylin
$ echo $PATH
/usr/lib64/qt-3.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/usr/local/rvm/bin:/home/kylin/.local/bin:/home/kylin/bin:/home/kylin/tools/apache-maven-3.2.5/bin:/usr/java/jdk1.8.0_25/bin:/home/kylin/tools/apache-ant-1.9.4/bin:/home/kylin/tools/node-v0.12.6-linux-x64/bin
  • Become the root user at the shell prompt.
$ su -
Password:
  • View the user and group information and display the current working directory.
# id
uid=0(root) gid=0(root) groups=0(root) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
# pwd
/root
  • View the variables which specify the home directory and the locations searched for executable files.
# echo $HOME
/root
# echo $PATH
/usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/.cabal/bin:/usr/local/rvm/bin:/root/bin
  • Exit the root
# exit
logout

Creating Users Using Command-line Tools

  • Add a user
# adduser student

Execute tail -2 /etc/passwd can confirm new added user from file.

  • Use the passwd command to add a login password
# passwd student

Managing Groups Using Command-line Tools

  • Create a group
# groupadd artists

Execute tail -5 /etc/group will confirm new added group.

  • Add a user to a group
# usermod -G student student
# id student 
uid=1001(student) gid=1002(student) groups=1002(student)

Managing User Password Aging

  • Lock/Unlock a user
# usermod -L student
$ su - student 
Password: 
su: Authentication failure

# usermod -U student
$ su - student 
Password: 
Last login: Tue Mar  8 15:30:03 CST 2016 on pts/1
Last failed login: Tue Mar  8 15:30:41 CST 2016 on pts/3
There was 1 failed login attempt since the last successful login.
  • Change the password policy to require a new password every 90 days
# chage -M 90 student
# chage -l student 
Last password change					: Mar 08, 2016
Password expires					: Jun 06, 2016
Password inactive					: never
Account expires						: never
Minimum number of days between password change		: 0
Maximum number of days between password change		: 90
Number of days of warning before password expires	: 7

Using Identity Management Services

//TODO–

File Permissions

Managing File Security from the Command Line

  • login to root, create a directory
# mkdir /home/kylin-text
  • Change the group ownership to kylin
# chown :kylin /home/kylin-text/
  • Ensure the permissions of kylin-text allows group members to create and delete files.
# chmod g+w /home/kylin-text/
  • Ensure the permissions of ateam-text forbids others from accessing its files.
# chmod 770 /home/kylin-text/
# ls -ld /home/kylin-text/
  • Verify the setting
# exit
logout
$ cd /home/kylin-text/
$ touch samplefile1
$ ls -l samplefile1 
-rw-rw-r--. 1 kylin kylin 0 Mar 10 11:27 samplefile1

Controlling New File Permissions and Ownership

  • show umask
[student@ksoong ~]$ umask 
0002
  • check default umask affects permissions
[student@ksoong ~]$ mkdir /tmp/shared
[student@ksoong ~]$ ls -ld /tmp/shared/
drwxrwxr-x. 2 student student 40 Mar 10 11:46 /tmp/shared/
[student@ksoong ~]$ touch /tmp/shared/defaults
[student@ksoong ~]$ ls -l /tmp/shared/defaults
-rw-rw-r--. 1 student student 0 Mar 10 11:47 /tmp/shared/defaults
  • do some change
[student@ksoong ~]$ chmod g+s /tmp/shared/
[student@ksoong ~]$ ls -ld /tmp/shared/
drwxrwsr-x. 2 student student 60 Mar 10 11:47 /tmp/shared/
[student@ksoong ~]$ umask 27
[student@ksoong ~]$ touch /tmp/shared/sameplefile2
[student@ksoong ~]$ ls -l /tmp/shared/sameplefile2 
-rw-r-----. 1 student student 0 Mar 10 11:52 /tmp/shared/sameplefile2
[student@ksoong ~]$ umask 
0027
[student@ksoong ~]$ umask 7

POSIX Access Control Lists (ACLs)

  • View file ACLs
$ getfacl gcviewer.properties 
# file: gcviewer.properties
# owner: kylin
# group: kylin
user::rw-
group::rw-
other::r--

Using ACLs to Grant and Limit Access

//TODO–

Selinux Permissions

//TODO–

Process Management

Killing Processes

  • Start 3 processes
$ (while true; do echo -n "game " >> ~/outfile; sleep 1; done) &
$ (while true; do echo -n "set " >> ~/outfile; sleep 1; done) &
$ (while true; do echo -n "match " >> ~/outfile; sleep 1; done) &
  • Check all running processes
$ tail -f outfile 
$ jobs
[1]   Running                 ( while true; do
    echo -n "game " >> ~/outfile; sleep 1;
done ) &
[2]-  Running                 ( while true; do
    echo -n "set " >> ~/outfile; sleep 1;
done ) &
[3]+  Running                 ( while true; do
    echo -n "match " >> ~/outfile; sleep 1;
done ) &
  • Kill process
$ kill -SIGTERM 7174
$ kill -SIGTERM 7187
$ kill -SIGTERM 7220

Monitoring Process Activity

  • Check cpu info
$ grep "model name" /proc/cpuinfo 
model name	: Intel(R) Core(TM) i5-4200U CPU @ 1.60GHz
model name	: Intel(R) Core(TM) i5-4200U CPU @ 1.60GHz
model name	: Intel(R) Core(TM) i5-4200U CPU @ 1.60GHz
model name	: Intel(R) Core(TM) i5-4200U CPU @ 1.60GHz
$ grep "model name" /proc/cpuinfo | wc -l
4
  • top commands
top
$ top -H -p 16943

Updating Software Packages