Data rotation and cleanup in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to list all files in the directory.

Raspberry Pi

import os
files = os.[1]('.')
print(files)

Drag options to blanks, or click blank then click option'

Alistdir

Brename

Cmkdir

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using os.remove instead of os.listdir

Trying to create a directory instead of listing files

The os.listdir function lists all files and folders in the given directory.

2fill in blank

medium

Complete the code to delete a file named 'old.log'.

Raspberry Pi

import os
os.[1]('old.log')

Drag options to blanks, or click blank then click option'

Alistdir

Bremove

Cmkdir

Drename

Attempts:

3 left

💡 Hint

Common Mistakes

Using os.listdir instead of os.remove

Trying to rename instead of delete

The os.remove function deletes a file given its path.

3fill in blank

hard

Fix the error in the code to rename 'temp.log' to 'backup.log'.

Raspberry Pi

import os
os.[1]('temp.log', 'backup.log')

Drag options to blanks, or click blank then click option'

Alistdir

Bremove

Cmkdir

Drename

Attempts:

3 left

💡 Hint

Common Mistakes

Using os.remove instead of os.rename

Trying to list files instead of renaming

The os.rename function renames or moves a file from the old name to the new name.

4fill in blank

hard

Fill both blanks to create a dictionary with file names as keys and their sizes as values for files larger than 1000 bytes.

Raspberry Pi

import os
files = os.listdir('.')
sizes = {file: os.path.[1](file) for file in files if os.path.[2](file) and os.path.[1](file) > 1000}

Drag options to blanks, or click blank then click option'

Agetsize

Bexists

Disfile

Attempts:

3 left

💡 Hint

Common Mistakes

Using os.path.exists instead of os.path.isfile

Not checking if the path is a file

os.path.getsize returns the size of a file. os.path.isfile checks if the path is a file.

5fill in blank

hard

Fill all three blanks to filter files with '.log' extension, get their sizes, and keep only those larger than 5000 bytes.

Raspberry Pi

import os
files = os.listdir('.')
log_files = {file: os.path.[1](file) for file in files if file.endswith('[2]') and os.path.[3](file) > 5000}

Drag options to blanks, or click blank then click option'

Agetsize

B.log

Disfile

Attempts:

3 left

💡 Hint

Common Mistakes

Not filtering by extension

Using wrong functions for size check

Use getsize to get file size, filter files ending with '.log', and check size greater than 5000 bytes.

Practice

1. What is the main purpose of data rotation and cleanup on a Raspberry Pi?

easy

A. To keep storage organized and remove old files

B. To increase the CPU speed

C. To install new software automatically

D. To change the screen resolution

Solution

1. Step 1: Understand data rotation and cleanup

   Data rotation and cleanup help manage files by removing old or unnecessary data.

2. Step 2: Identify the main goal

   The goal is to keep storage organized and free space by deleting old files.

3. Final Answer:

   To keep storage organized and remove old files -> Option A

4. Quick Check:

   Data rotation = storage cleanup [OK]

Hint: Think about storage space and file management [OK]

Common Mistakes:

• Confusing data cleanup with hardware upgrades
• Thinking it changes system performance directly
• Assuming it installs software automatically

2. Which of the following commands correctly deletes files older than 7 days in the /var/log directory on Raspberry Pi?

easy

A. find /var/log -type d -mtime +7 -delete

B. find /var/log -type f -mtime +7 -delete

C. rm /var/log/* -mtime +7

D. delete /var/log -older 7

Solution

1. Step 1: Understand the find command syntax

   To delete files older than 7 days, use find with -type f (files), -mtime +7 (older than 7 days), and -delete.

2. Step 2: Check each option

   find /var/log -type f -mtime +7 -delete uses correct syntax. find /var/log -type d -mtime +7 -delete targets directories (-type d), not files. rm /var/log/* -mtime +7 uses rm incorrectly with -mtime. delete /var/log -older 7 is not a valid command.

3. Final Answer:

   find /var/log -type f -mtime +7 -delete -> Option B

4. Quick Check:

   find + -mtime +7 + -delete = correct [OK]

Hint: Use find with -type f and -mtime +days to delete old files [OK]

Common Mistakes:

• Using -type d instead of -type f
• Trying to use rm with -mtime option
• Using invalid commands like delete

3. What will be the output of this script snippet on Raspberry Pi?

logfile="/var/log/syslog"
backup="/var/log/syslog-$(date +%Y%m%d)"

mv $logfile $backup
> $logfile
ls /var/log/syslog*

medium

A. Only /var/log/syslog-YYYYMMDD file listed

B. Only /var/log/syslog file listed

C. /var/log/syslog and /var/log/syslog-YYYYMMDD files listed

D. No files listed, error occurs

Solution

1. Step 1: Understand the script actions

   The script renames syslog to syslog-YYYYMMDD (today's date), then creates a new empty syslog file.

2. Step 2: Predict the ls output

   After these steps, both /var/log/syslog (empty) and /var/log/syslog-YYYYMMDD exist, so ls lists both.

3. Final Answer:

   /var/log/syslog and /var/log/syslog-YYYYMMDD files listed -> Option C

4. Quick Check:

   mv + new empty file + ls = both files [OK]

Hint: Renaming then recreating file shows both in listing [OK]

Common Mistakes:

• Thinking syslog file is deleted
• Assuming mv copies instead of moves
• Ignoring the empty file creation with >

4. Identify the error in this Raspberry Pi log rotation script snippet:

logfile="/var/log/app.log"
backup="/var/log/app.log-$(date +%Y%m%d)"

mv $logfile $backup
> $logfile
find /var/log -type f -mtime 7 -delete

medium

A. The find command should use -mtime +7 to delete files older than 7 days

B. The mv command syntax is incorrect

C. The > $logfile line should be before mv command

D. The backup filename format is invalid

Solution

1. Step 1: Check the find command usage

   The find command uses -mtime 7 which matches files exactly 7 days old, not older than 7 days.

2. Step 2: Correct the find command

   To delete files older than 7 days, use -mtime +7 instead of -mtime 7.

3. Final Answer:

   The find command should use -mtime +7 to delete files older than 7 days -> Option A

4. Quick Check:

   find -mtime +7 deletes older files [OK]

Hint: Use + before days in -mtime to delete older files [OK]

Common Mistakes:

• Using -mtime 7 deletes only files exactly 7 days old
• Misplacing the > $logfile line
• Incorrect mv command syntax

5. You want to automate log rotation on your Raspberry Pi so that every day the current log file /var/log/myapp.log is renamed with the date, a new empty log is created, and logs older than 14 days are deleted. Which script snippet correctly performs this task?

hard

A. mv /var/log/myapp.log /var/log/myapp.log-$(date +%Y%m%d)
> /var/log/myapp.log
find /var/log -type f -name 'myapp.log-*' -mtime 14 -delete

B. mv /var/log/myapp.log /var/log/myapp.log-$(date +%Y%m%d)
rm /var/log/myapp.log
find /var/log -type f -mtime +14 -delete

C. backup="/var/log/myapp.log-$(date +%Y%m%d)"
cp /var/log/myapp.log $backup
> /var/log/myapp.log
find /var/log -type f -name 'myapp.log-*' -mtime 14 -delete

D. backup="/var/log/myapp.log-$(date +%Y%m%d)"
mv /var/log/myapp.log $backup
> /var/log/myapp.log
find /var/log -type f -name 'myapp.log-*' -mtime +14 -delete

Solution

1. Step 1: Rename current log and create new empty log

   backup="/var/log/myapp.log-$(date +%Y%m%d)" mv /var/log/myapp.log $backup > /var/log/myapp.log find /var/log -type f -name 'myapp.log-*' -mtime +14 -delete correctly moves the log file to a dated backup and creates a new empty log with >.

2. Step 2: Delete logs older than 14 days

   backup="/var/log/myapp.log-$(date +%Y%m%d)" mv /var/log/myapp.log $backup > /var/log/myapp.log find /var/log -type f -name 'myapp.log-*' -mtime +14 -delete uses find with -name 'myapp.log-*' and -mtime +14 to delete backups older than 14 days, which is correct.

3. Final Answer:

   backup="/var/log/myapp.log-$(date +%Y%m%d)" mv /var/log/myapp.log $backup > /var/log/myapp.log find /var/log -type f -name 'myapp.log-*' -mtime +14 -delete -> Option D

4. Quick Check:

   mv + new file + find -mtime +14 = correct rotation [OK]

Hint: Move log, recreate empty, delete backups older than 14 days [OK]

Common Mistakes:

• Using rm instead of recreating empty log
• Using -mtime 14 instead of +14 in find
• Copying instead of moving log file