LFCA case studies
LFCA · Put your knowledge to work in context.
The Linux Foundation Certified IT Associate (LFCA) is an entry-level, pre-professional certification aimed at people who are new to IT or considering a first role as an administrator or engineer. The source describes it as a stepping stone: it confirms early proficiency and aptitude and is intended to integrate with other qualifications on the way to more advanced credentials. The LFCA case studies are 5 cases and about 3,689 words.
1Ext4 Reports 100% Full While du Sums to 3.8 GiB
An Ubuntu 22.04 web server keeps /var on its own 20 GiB ext4 partition. Monitoring pages at 03:10 because df -h /var reports 100% used, yet du -sh /var sums to only 3.8 GiB and df -i shows IUse% at 4%.
744 words, about 4 min2Backup Unit Succeeds Manually but Fails in the Patch Window
On Ubuntu 22.04, backup.service (Type=oneshot, User=backup, Wants=network.target , After=network.target ) runs /usr/local/bin/pg-backup.sh , and backup.timer triggers it daily at 02:30. The script runs pg dump -Fc against pg-prod-01 at 10.20.0.15:5432, then rclone sync to object storage.
716 words, about 4 min3Burstable Instance Degrades Every Morning at Ten
A team lifts a Java order-intake service from a 4 vCPU / 8 GiB on-premises VM to a single AWS t3.medium (2 vCPU, 4 GiB) in one Availability Zone, leaving PostgreSQL on a t3.small in the same subnet. CloudWatch shows the instance at 90-98% CPU between 08:00 and 19:00, idle overnight, plus a reconciliation batch at 02:00 that pins both vCPUs for about an hour.
726 words, about 4 min4SSH Brute Force, Stale Keys, and a Stolen Laptop
bastion-01 is the only internet-facing host. Its auth.log shows about 3,900 failed root password attempts in 24 hours from 40 source IPs.
748 words, about 4 min5Two Percent of Requests Return 502 at Peak
A Django API runs under gunicorn in one container on a 2 vCPU VM behind nginx, started with --workers 4 --threads 2 --timeout 30 (the default). Baseline p95 is 180 ms, but p99 is 4.6 s, and during the 09:00-10:00 peak about 2.1% of requests return 502.
755 words, about 4 min