Lesson 1

Date: 5/28/2014
User accounts, files and directories, processes, system commands.
Linux System Administration


Systems commands


Directory Manipulation

When you login into the system, you automatically get into your home directory
1. Determine the directory you are in:
      pwd 
2. Go to some other directory, for example, /etc:
      cd /etc 
3. Go to your home directory:
      cd $HOME
      or
      cd ~
4. Go back-and-forth between directories and check where you are:
      cd /etc
      pwd
      cd -
      pwd
      cd -
      pwd
5. Create a new directory above your home directory:
      mkdir Newdir 
6. Go to the new directory and check where you are:
      cd Newdir
      pwd 
7. Go one step back to the parent directory and check where you are:
   
      cd ..
      pwd
8. Remove the new directory:
      rmdir Newdir 
9. Create a new directory above your home directory with subdirectories. Try the following:
      mkdir Newdir/one/two/three 
Does it work? Try the following:
      mkdir -p Newdir/one/two/three 
10. Create a few files in Newdir/one:
      cd Newdir/one; touch f1.t; touch f2.t; touch f3.t 
11. Go back into the original directory and try to delete Newdir:
      cd -
      rmdir Newdir 
Does it work ? Try the following:
 
      rm -R Newdir 
12. Repeat step #10; Copy the directory with its tree into another directory:
      cp -dpR Newdir Newdir-1 
same as
      cp -a Newdir Newdir-1 

13. Show content of file /etc/hosts
 
cat /etc/hosts 
tac /etc/hosts 
less /etc/hosts
14. Show the first and last 10 lines of a file
 
head -n 10 /etc/nsswitch.conf   
tail -n 10 /etc/nsswitch.conf     
15. Show date on the system clock
 
date 
16. File system usage
 
df -h
17. Disk usage
du -h /home             
du -s /home             
du --max-depth=1 /var    
du -x /                  
du -x /home               
du -x /usr           
18. Display data
echo $[10*3+2]             
echo '$[10*3+2]'          
echo "$[10*3+2]"    
19. Determine file type
file /bin/ls  
file /etc/hosts 
20. Who is logined to the system
who
21. The owner of the current shell
whoami
22. Getting information about a file or command, for example netstat
whatis netstat
apropos netstat 
man netstat
info netstat

23. Compressing/uncompressing files with gzip, and bzip2:
cd ~                             
cp /etc/hosts  hosts.txt      
gzip hosts.txt                
ls -l                          
less hosts.txt.gz             
more hosts.txt.gz             
zcat hosts.txt.gz              
gzip -d hosts.txt.gz           
bzip2 hosts.txt
bzip2 -d hosts.txt.bz2
24. Searching for files by using command find
cd /tmp                            
mkdir newfiles; cd newfiles        
touch fff.txt                      
cd ~                                
find / -name fff.txt                
cd /tmp                             
find . -name fff.txt                 
find . -name '*ff*'                   
find /tmp -name fff.txt -exec rm '{}' ';'    
find /var -size +1000k                     
find /var -size +1000000c                   
find /home -user hostadm              
find /var -mtime -5                           
find /var -maxdepth 2 -mtime -20    
25. Searching for system files
which dpkg 
whereis dpkg 
locate dpkg

26. Using tar-gzip to archive a directory.
Create a new directory with subdirectories above your home directory, then tar and gzip it. For example,
mkdir -p Newdir/one/two/three          
cd Newdir/one/two                      
cp /etc/hosts .                         
cd three                                 
cp /etc/passwd .                         
cd ~
tar -cvf Newdir.tar Newdir
gzip Newdir.tar
ls -l Newdir.tar.gz
rm -R Newdir
cp Newdir.tar.gz /tmp
cd /tmp
gzip -d Newdir.tar.gz
tar -xvf Newdir.tar 
27. To tar and gzip file with one command, try the following:
tar -zcvf Newdir.tgz Newdir         
rm -R Newdir                         
ls -l Newdir.tgz                     
tar -zxvf Newdir.tgz       
28. Archive/restore from input file list by cpio command:
cd /etc
find . | cpio -ov  > /tmp/etc.cpio
mkdir /tmp/RESTORE
cd /tmp/RESTORE
cpio -iv < ../etc.cpio

29. Command history in bash shell:
history
Find a command in the history by the regular expression in its name:
ctrl + R
then type the string contained in the command.
30. Command history file .bash_history is updated when a user exits the shell.
tail .bash_history
The size or file .bash_history is defined by env variable HISTSIZE
echo $HISTSIZE


  • Reference: Basic System Commands



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