linuxexpert-practice-labs/labs/ubuntu-server/3-2-regular-and-system-users

Ubuntu Server 3.2: Regular and system users

Telling login accounts from system accounts, a system user for a service, and a service that runs as it.

Before you start

The lab adds a few accounts so the lists in task 1 have something to tell apart: maria (a regular user with a shell), kiosk (a regular UID with no login shell) and buildbot (a system UID with a shell). Write answers to the files in /root/lab-answers/, one account name per line.

Tasks

1. List every account that can log in with a shell, into /root/lab-answers/1-shells, and every account with a UID of 1000 or more, into /root/lab-answers/1-uids.
2. Create a system user reportsvc with its own group, a data directory /var/lib/reportsvc that only it can write to, and no login. sudo -u reportsvc touch /var/lib/reportsvc/ok works and sudo -u reportsvc touch /etc/ok fails.
3. Run a python3 -m http.server 8080 service as reportsvc with a systemd unit, started at boot. curl -s localhost:8080 | head -1 prints HTML.

Hints

• /etc/passwd: the UID is field 3 and the shell field 7. grep -v -E 'nologin|false|sync$' /etc/passwd, awk -F: '$3>=1000', cut -d: -f1.
• useradd --system --user-group --shell /usr/sbin/nologin, id, getent passwd; install -d -o -g -m 755.
• User=, WorkingDirectory= in a unit in /etc/systemd/system/; systemctl enable --now; ps -o user= -C python3.