Table of contents
1. Daemon
1.1. Python script
Write a Python script that periodically calculates the total size of all files in a specified directory (including all its subdirectories) and logs the date, time, and total size when it exceeds a given threshold expressed in bytes. In your home directory, create the directory dir-size-monitor and, inside it, the file app.py, using this template:
# first and last name:
# student id:
#
# path:
import argparse
from datetime import datetime
import os
import sys
import time
def main():
pass
if __name__ == "__main__":
main()The script must accept exactly four mandatory command-line arguments, parsed with the argparse module: --target, which specifies the absolute path of the directory to monitor; --threshold, which specifies the threshold in bytes (positive integer) above which a warning must be logged; --interval, which defines the interval in seconds (positive integer) between each check; and --log, which specifies the absolute path of the directory where to save the log file. The name of the log file is always dir-size-monitor.log.
After parsing, validate the received inputs: verify that the path specified with --target is absolute (os.path.isabs), that it exists (os.path.exists), and that it is a directory (os.path.isdir); also check that the values provided for --threshold and --interval are positive integers; verify that the path indicated with --log exists, that is a directory, and that is absolute. If any check fails, print an explanatory error message to standard error (print) and exit with a non-zero status code (sys.exit).
After validation, recursively traverse the directory tree at the path provided with --target (os.listdir, os.path.join, os.path.isdir). For each file encountered (os.path.isfile), get its size (os.path.getsize) and add it to an accumulator to calculate the total size of the directory. If the total size is greater than or equal to the threshold indicated by --threshold, open in append mode the log file dir-size-monitor.log in the directory specified with --log (open) and write a line containing the current date and time (datetime.now), a space, and the total size in bytes. The script must repeat this procedure periodically, waiting for a number of seconds equal to the value indicated by --interval between each check (time.sleep).
For example, running:
$ python ~/dir-size-monitor/app.py \
--target ~/documents \
--threshold 1000 \
--interval 60 \
--log ~the script will calculate the total size of all files in ~/documents (and in all its subdirectories) and, if that size is greater than or equal to 1000 bytes, will append to ~/dir-size-monitor.log the date, time, and total size. The script will repeat the operation every 60 seconds.
1.2. Service
Create a service unit named dir-size-monitor.service in your user instance of systemd. The unit must start ~/dir-size-monitor/app.py with the arguments --target %h/documents, --threshold 1000, --interval 60, and --log %h, start at system boot, and restart in case of failures. Use this template:
# first and last name:
# student id:
#
# path:
#
# command to enable the service:
# command to start the service:
1.3. Solution
This exercise was proposed on February 9, 2026.
2. Account administration
2.1. Text
Configure sudo on a fleet of four Linux hosts: three cache hosts (cache01, cache02, cache03) and a gateway host (gateway01). The fleet has the following users and groups:
| User | Primary group | Additional groups |
|---|---|---|
liam | liam | |
mia | mia | ops |
noah | noah | ops |
olivia | olivia | audit |
Apply the following rules:
| Category | Rule |
|---|---|
| Aliases | Define Host_Alias CACHE = cache01, cache02, cache03 |
| Aliases | Define Cmnd_Alias SHELLS = /bin/sh, /bin/dash, /bin/bash, Cmnd_Alias NETMGM = /usr/bin/ss, /usr/bin/ip, and Cmnd_Alias BACKUP = /usr/bin/rsync, /usr/bin/tar |
| Permissions | liam can run any command as any user on any host |
| Permissions | mia can run any command as any user on any host, except SHELLS |
| Permissions | %ops can run NETMGM as root on CACHE |
| Permissions | %audit can run BACKUP as root on gateway01, without a password |
| Permissions | noah can run /usr/bin/tail -f /var/log/syslog as root on any host, without a password |
| Permissions | olivia can run /usr/bin/id as mia on CACHE |
| Permissions | %ops, %audit can run /usr/sbin/reboot as root on any host, without a password |
The file must be created at /etc/sudoers.d/local. Use this template:
# first name and last name:
# student id:
#
# path:
2.2. Solution
# first name and last name: mattia fogli
# student id: 123456
#
# path: /etc/sudoers.d/local
Host_Alias CACHE = cache01, cache02, cache03
Cmnd_Alias SHELLS = /bin/sh, /bin/dash, /bin/bash
Cmnd_Alias NETMGM = /usr/bin/ss, /usr/bin/ip
Cmnd_Alias BACKUP = /usr/bin/rsync, /usr/bin/tar
liam ALL = (ALL) ALL
mia ALL = (ALL) ALL, !SHELLS
%ops CACHE = NETMGM
%audit gateway01 = NOPASSWD: BACKUP
noah ALL = NOPASSWD: /usr/bin/tail -f /var/log/syslog
olivia CACHE = (mia) /usr/bin/id
%ops, %audit ALL = NOPASSWD: /usr/sbin/reboot
Licenses
| Content | License |
|---|---|
| Code | MIT License |
| Text | Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International |