1. List All Files in the /etc/ Directory

Use the ls command to view all file information in the /etc/ diretcory.

Common ls options:

• -l: Display file information in long format
• -A: Show all files, including hidden files starting with .
• -a: Show all files, including . and ..
• -d: Display properties of the directory itself (not its contents)
• -h: Provide human-readable size units (K, M, etc.)
• -s: Show disk space usage for each file

$ ls -la /etc

2. List Files or Directories Containing the Letter "a" in /etc/

$ ls -d /etc/*a*/

3. List Files Ending with ".conf" in /etc/

$ ls -l /etc/*.conf

4. List Files Starting with "y" in /etc/

$ ls -l /etc/y*

5. Find Files with ".log" Extension in /var/ Directory

Basic find syntax: find [path] [option value]

• -name: Search files by name (supports wildcards like *)
• -type f: Regular files
• -type d: Directories

$ find /var/ -name "*.log" -type f

6. Create a Test Directory in /opt

$ mkdir /opt/test

7. Create Five Files in the Test Directory

$ cd /opt/test
$ touch abc.txt def.txt ghi.txt xxx.txt yyy.txt
$ ls
abc.txt  def.txt  ghi.txt  xxx.txt  yyy.txt

8. Modify the Last Modification Times of the Five Files

Use stat to get file time information:

$ stat /opt/test/abc.txt

Modify or set the modification time:

$ touch -m -d "2024-07-15 00:00" /opt/test/abc.txt
$ touch -m -d "2024-07-14 00:00" /opt/test/def.txt
$ touch -m -d "2024-07-13 00:00" /opt/test/ghi.txt
$ touch -m -d "2024-07-12 00:00" /opt/test/xxx.txt
$ touch -m -d "2024-07-11 00:00" /opt/test/yyy.txt

9. Create Directory a in the Test Directory

$ mkdir /opt/a
$ ls /opt
a  test

10. Copy the Five Files to Directory a

cp — Copy files Format: cp [options] source_file... target_path Common option:

• -r: Recursive (required for copying directories)

$ cp -r abc.txt def.txt ghi.txt xxx.txt yyy.txt /opt/a/
$ ls
abc.txt  def.txt  ghi.txt  xxx.txt  yyy.txt
$ cd /opt/a
$ ls
abc.txt  def.txt  ghi.txt  xxx.txt  yyy.txt

11. Create a Compressed Archive of Directory a in the Home Directory

tar creates compressed archives with minimal disk space usage. Compression formats:

• .gz: gzip format (fast compression)
• .bz2: bzip2 format
• .xz: xz format (smaller size)

Compress: tar [options] /path/archive_name /files_to_compress... Extract: tar [options] /path/archive [options] /target_location

Common tar options:

• -c: Create archive
• -x: Extract archive
• -f: Specify archive filename
• -z, -j, -J: Use gzip, bzip2, or xz compression
• -t: List archive contents
• -C: Specify extraction directory

$ tar -zcf /home/bak.tar.gz .
$ ls /home
bak.tar.gz

12. Delete Files Older Than 3 Days in the Test Directory

Search by modification time: find path -mtime -days/+days

• -mtime: Search by last modification time
• +: Files older than specified days
• -: Files within specified days
• -exec rm -rf {} \;: Execute rm -rf on each found file

$ find /opt/test -type f -mtime +3 -exec rm -f {} \;
$ ls /opt/test
abc.txt  def.txt  ghi.txt

13. Delete Files Within 3 Days in /opt Directory

$ find . -type f -mtime -3 -exec rm -f {} \;  # . represents current directory
$ ls  # a and test are directories, not files
a  test

14. Delete Files Exactly 3 Days Old

$ find /opt/test -type f -mtime 2 -exec rm -f {} \;  # -mtime 2 selects files modified exactly 3 days ago
$ ls /opt/test
ghi.txt

15. Copy Files from /opt/test/a to /opt/test/

$ find /opt/test/a -type f -exec cp --parents \{\} /opt/test \;  # Copy files while preserving directory structure

16. Create Directory /opt/test0

$ mkdir /opt/test0

17. Create Three Files with Specific Sizes in /opt/test0/

Use dd to create test files of specified sizes. Syntax: dd if=/dev/zero of=filename bs=size count=1

• if: Input file
• of: Output file
• bs: Block size in bytes
• count: Number of blocks to copy
• /dev/zero: Character device that returns zero bytes

$ cd test0
$ dd if=/dev/zero of=a.mp4 bs=5M count=1
$ dd if=/dev/zero of=b.mp4 bs=20M count=1
$ dd if=/dev/zero of=c.mp4 bs=80M count=1
$ ls
a.mp4  b.mp4  c.mp4

18. Create Directory /opt/test0/b/

$ mkdir b
$ ls
a.mp4  b  b.mp4  c.mp4

19. Copy Files from /opt/test0/ to /opt/test0/b/

$ cp -r a.mp4 b.mp4 c.mp4 /opt/test0/b/
$ ls /opt/test0/b/
a.mp4  b.mp4  c.mp4

20. Find and Delete Files Larger Than 20M in /opt/test0/

Search by file size: find path -size size [units K M G]

• size: Files equal to size
• -size: Files in range [0, size)
• +size: Files in range (size, infinity)

$ find /opt/test0/ -size +20M -exec rm -rf {} \;
$ ls
a.mp4  b  b.mp4

21. Find and Delete Files Smaller Than 20M in /opt/test0/

$ find /opt/test0/ -type f -size -20M -delete
$ ls
b  b.mp4

22. Find and Delete Files Exactly 20M in /opt/test0/

$ find /opt/test0/ -size 20M -exec rm -rf {} \;
$ ls
b

23. Copy Files from /opt/test0/b to /opt/test0

$ cp a.mp4 b.mp4 c.mp4 /opt/test0
$ cd /opt/test0
$ ls
a.mp4  b  b.mp4  c.mp4

24. Open a New Virtual Machine

25. Upload bak.tar.gz from Home Directory to New Machine's /opt

Use scp to transfer files. Syntax: scp [options] username@host:/remote_path local_path

$ scp root@192.168.2.4:/home/bak.tar.gz /opt/
Are you sure you want to continue connecting (yes/no)? yes
root@192.168.2.4's password:
bak.tar.gz                    100%  177   108.1KB/s   00:00
$ ls /opt
bak.tar.gz

26. Download /etc/skel/ Directory from New Machine to Local /opt

Add -r option for recursive directory copying.

$ scp -r root@192.168.2.3:/etc/skel/ /opt/
root@192.168.2.3's password:
.bash_logout                  100%   18     7.4KB/s   00:00
.bash_profile                 100%  193   105.1KB/s   00:00
.bashrc                       100%  231   125.2KB/s   00:00
$ ls /opt
a  skel  test  test0

27. Schedule Weekly Compression of .repo Files with Timestamp

Use crontab for scheduling tasks. Options:

• -l: List current user's scheduled tasks
• -e: Edit scheduled tasks

Crontab format: minute hour day month weekday command_path (0 and 7 both represent Sunday)

$ crontab -e
0 0 * * 3 /usr/bin/tar -zcvf /tmp/yum-$(date "+\%Y\%m\%d\%H\%M\%S").tar.gz /etc/yum.repos.d/*.repo
crontab: installing new crontab
$ ls -l /tmp/
total 0