RHCSA EX200 - Input/Output Redirection LAB

Use Input/Output Redirection

Create a Server Health Log File

1. Create a server health log file that contains a sequential number of outputs with the hostname, date and time, and a simple header:

   cloud_user@server1: ~ $ { echo " " ; echo "==== `date` on `hostname` ====" ; df -hT ; }
    
   ==== Wed May  1 20:53:07 UTC 2024 on server1 ====
   Filesystem     Type      Size  Used Avail Use% Mounted on
   devtmpfs       devtmpfs  1.8G     0  1.8G   0% /dev
   tmpfs          tmpfs     1.9G     0  1.9G   0% /dev/shm
   tmpfs          tmpfs     1.9G   17M  1.9G   1% /run
   tmpfs          tmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup
   /dev/xvda2     xfs        20G   14G  6.7G  67% /
   tmpfs          tmpfs     373M  4.0K  373M   1% /run/user/1001
   

2. Rerun the previous command, and output this to a text file:

   { echo " " ; echo "==== `date` on `hostname` ====" ; df -hT ; } > `hostname`-health.txt
   

3. Review the output:

   cloud_user@server1: ~ $ cat server1-health.txt 
    
   ==== Wed May  1 20:53:51 UTC 2024 on server1 ====
   Filesystem     Type      Size  Used Avail Use% Mounted on
   devtmpfs       devtmpfs  1.8G     0  1.8G   0% /dev
   tmpfs          tmpfs     1.9G     0  1.9G   0% /dev/shm
   tmpfs          tmpfs     1.9G   17M  1.9G   1% /run
   tmpfs          tmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup
   /dev/xvda2     xfs        20G   14G  6.7G  67% /
   tmpfs          tmpfs     373M  4.0K  373M   1% /run/user/1001
   

   Observe what was added to the file.

4. Rerun the first echo command to create the server health log file twice more:

   { echo " " ; echo "==== `date` on `hostname` ====" ; df -hT ; } > `hostname`-health.txt
   

5. Review the output using cat server1-health.txt again to see how many times the command was run.

6. Change the server health log file to contain a double redirect to ensure that the initial and subsequent outputs are not overwritten:

   { echo " " ; echo "==== `date` on `hostname` ====" ; df -hT ; } >> `hostname`-health.txt
   

7. Run the above command 2 more times.

8. Inspect the output again using cat server1-health.txt.

Search for Files in the /home Directory

1. Find all the files in the /home directory owned by the cloud_user:

   find /home -user cloud_user
   

   Observe a long list of filenames, along with 2 Permission denied errors at the end.

2. Generate clean lines of output without the 2 errors:

   find /home -user cloud_user 2> /dev/null
   

3. Find out how many clean lines of output there are:

   find /home -user cloud_user 2> /dev/null | wc -l
   

4. Save the output to a text file:

   find /home -user cloud_user 2> /dev/null > cloud_user-files.txt
   

5. Ensure the filenames are in the text file:

   cat cloud_user-files.txt
   

6. Number the list of filenames, and save them in another text file:

   nl cloud_user-files.txt > numberedfiles.txt
   

7. Ensure the numbered filenames are in the text file:

   cat numberedfiles.txt
   

8. Sort the numbered lines:

   sort numberedfiles.txt
   

   Observe that because there were no leading zeroes in front of the lower numbers, it doesn't sort properly.

9. To fix this, run a numeric sort:

   sort -n numberedfiles.txt
   

10. Generate a list showing the first-level directories inside /etc:

    find /etc -maxdepth 1
    

    Observe the output includes files that go 1 level further than then /etc directory.

11. Add on to the previous command to generate a list showing the space used for the first-level directories inside /etc:

    find /etc -maxdepth 1 -iname "*.*" -exec du -sh {} \;
    

    Observe the previous list now includes total space usage for each item.

12. Rerun the following command, and sort it by space usage from least to most used:

    find /etc -maxdepth 1 -iname "*.*" -exec du -sh {} \; | sort -h
    

13. Rerun the previous command, and this time, output it to etc-space-usage.txt:

    find /etc -maxdepth 1 -iname "*.*" -exec du -sh {} \; | sort -h > etc-space-usage.txt
    

    You shouldn't see any output aside from 2 directory errors.

14. Review the file:

    less etc-space-usage.txt
    

    Observe the files listed and sorted by space usage.

Use grep and Regular Expressions to Analyze Text

1. Find all the files owned by the cloud_user in the /home directory:

   find /home -user cloud_user
   

2. Find all the files owned by the cloud_user in the /home directory that contain the word "file":

   cloud_user@server1: ~ $ find /home -user cloud_user | grep -i file
   /home/cloud_user/.bash_profile
   find: ‘/home/ssm-user’/home/cloud_user/numberedfiles.txt
   /home/cloud_user/cloud_user-files.txt
   : Permission denied
   find: ‘/home/devops’: Permission denied
   

   Notice in the output that it only searches for the word "file" in the actual filenames rather than within the contents of the file.

3. Use the -exec feature of find to find the word "file" in the files themselves:

   find /home -user cloud_user -exec grep -i file {} \;
   

4. Find out how many lines of output were found:

   find /home -user cloud_user -exec grep -i file {} \; | wc -l
   

   You should see 140 lines at the bottom of the output.

5. Count how many lines were generated without errors:

   find /home -user cloud_user -exec grep -i file {} \; 2> /dev/null | wc -l
   

   You should again see 140 lines. Note that this counts only the standard out rather than the standard error.

6. Utilize the grep command directly to find the word "file" inside all files owned by cloud_user in the /home directory:

   grep -ir file /usr/share/doc/zip
   

7. Add a total count of the output to the bottom of the list:

   grep -ir file /usr/share/doc/zip ; !! | wc -l
   

   You should see 965 at the bottom.

8. Run a case-sensitive search for only the word "file" as lowercase:

   grep -ir file /usr/share/doc/zip ; grep -r file /usr/share/doc/zip | wc -l
   

   You should see 925 at the bottom.

9. Create a text file containing all the search results for the word "file":

   grep -ir file /usr/share/doc/zip ; grep -r file /usr/share/doc/zip > grepoutput.txt
   

10. Check the text file output:

    cat grepoutput.txt