LFCS case studies
LFCS · Put your knowledge to work in context.
The Linux Foundation Certified System Administrator (LFCS) is a vendor-neutral, performance-based certification that validates practical Linux administration skill rather than multiple-choice recall. It suits intermediate-level practitioners - system administrators, DevOps and support engineers - who already work comfortably at a shell and want a credential that is not tied to a single distribution. The LFCS case studies are 5 cases and about 3,316 words.
1reportd restart loop after reboot: ordering versus directory readiness
On an Ubuntu 22.04 host you deploy a Go binary at /opt/reportd/reportd with unit /etc/systemd/system/reportd.service: ExecStart=/opt/reportd/reportd --config /etc/reportd/config.yaml, User=reportd, After=network.target, Restart=always, RestartSec=5. Running that exact command line as root works.
536 words, about 3 min2SSH sessions hang on a dual-homed server: wrong prefix length, not a firewall
A Debian 12 server has two NICs: eth0 10.20.0.10/24 with default route via 10.20.0.1, and eth1 192.168.50.10 configured with a 32-bit mask (a typo made during a late-night change). A static route 192.168.0.0/16 via 10.20.0.1 exists for a legacy subnet.
693 words, about 3 min3Extending /var online when the numbers on the screen are misleading
A web server VM has one 40 GB disk, VG vg0 with lv root (ext4, mounted /) and lv var (ext4, mounted /var). df -h /var reports 1.9 GB free; vgs reports 30 GB free in vg0; df -i shows 12% inode use.
525 words, about 3 min4A 900 GB log directory with 2 million files and a daemon holding deleted inodes
On a RHEL 9 host, /var/log/app holds roughly 2 million files spread across 400 subdirectories written by a vendor daemon. du -sh /var/log/app reports 900 GB and the volume is full.
733 words, about 4 min5A setgid share that still is not writable, and a narrowly scoped sudo rule that is not narrow
A shared build area /srv/build is owned root:devs with mode 2775. alice, bob and carol are members of devs.
829 words, about 4 min