CompTIA Linux+ case studies
CompTIA Linux+ · Put your knowledge to work in context.
CompTIA Linux+ (V8) is a vendor-neutral certification, exam series XK0-006, that validates the ability to manage, secure, automate, and troubleshoot Linux systems in cloud and hybrid environments. It launched on July 15, 2025, and is aimed at practitioners who already have roughly 12 months of hands-on experience with Linux servers; CompTIA A+, Network+, or Server+ (or comparable knowledge) is recommended before you start. The CompTIA Linux+ case studies are 5 cases and about 3,539 words.
1The 38 GB That du Cannot See
A monitoring alert reports that /var on an Ubuntu 22.04 web server is at 100% (50 GB volume, 0 bytes available). The site returns 500 errors because PHP session files cannot be written.
707 words, about 4 min2Group Membership That Never Reaches the Process
An internal team ships reporting.service on Ubuntu 22.04 with User=svc-report , Group=svc-report , Restart=on-failure , and ExecStart=/opt/reporting/bin/run --out /srv/data . The data directory is drwxrws--- root data-readers .
688 words, about 3 min3Key Auth Broken After a CIS Hardening Window
A Rocky Linux 9 host runs OpenSSH 8.7 with SELinux enforcing and firewalld. After a CIS hardening role ran, key-based login for deploy stopped working: ssh -v deploy@host shows the key being offered and then Permission denied (publickey,gssapi-keyex,gssapi-with-mic) .
565 words, about 3 min4The Cron Job That Only Works When a Human Watches
A Debian 12 report pipeline runs from root's crontab: /15 /usr/local/bin/sync reports.sh /var/log/sync.log 2 &1 . After a host rebuild the script works when run by hand as root but logs python3: command not found under cron; a later edit made it run without errors yet produce empty CSV files.
835 words, about 4 min5Emergency Mode After an fstab Edit
A RHEL 9 server was rebooted after an admin added nfsserver:/export/archive /mnt/archive nfs defaults 0 0 to /etc/fstab. The NFS server is in another datacenter and is down for scheduled maintenance.
744 words, about 4 min