Page 7 - Linux

Once more than a single IP address needs managing, for example a filesystem, a database and a service all becoming resilient together, keepalived is no longer enough. Pacemaker and Corosync together form the standard Linux cluster stack that monitors, starts and relocates arbitrary resources in a coordinated way on failure.

When development environments, databases and Docker containers live on a remote server, the quality of the SSH connection decides whether the work feels local or like a constant compromise. With a clean SSH config, VS Code Remote-SSH and targeted port forwarding, the remote server becomes a seamless extension of your own development environment.

A highly available cluster is only as good as the storage underneath it. As soon as application servers need to see the same files or data must survive a node failure, a distributed filesystem becomes a basic requirement, and the choice between GlusterFS, Ceph, NFS and DRBD determines performance, complexity and actual failure resistance.

Incorrectly set file permissions are one of the most common causes of hacked web servers and broken deployments. This guide explains the read/write/execute model, symbolic and octal chmod notation, the difference between chmod and chown, and a battle-tested permission baseline for Magento web roots with www-data ownership, 755 for directories, and 644 for files.

Compliance automation with OpenSCAP turns manual, error prone checklists into repeatable scans against recognized SCAP profiles. Using the SCAP Security Guide correctly, generating automatic remediation scripts and running the process continuously via Ansible and oscapd turns compliance into an observable operational state instead of a one time preparation for an audit.

A cron job that runs longer than its scheduled interval quietly starts a second time, even though the first run has not finished yet. Two parallel database exports, two simultaneous backup processes, or two import scripts blocking each other are the result, often without an immediately visible error message. This article shows how flock reliably prevents overlapping cron jobs, both directly in crontab and inside scripts, and where the limits of simpler locking approaches lie.

A single server is always a single point of failure. keepalived solves this problem with the VRRP protocol, letting two or more Linux servers share a virtual IP address and take over automatically on failure, with no expensive hardware load balancer required.

sysfs maps every kernel object, driver and detected device as a plain file under /sys. Understanding this structure lets you diagnose hardware states, tune block device schedulers and change kernel module parameters at runtime, without extra tools or a reboot.

A reliable backup concept combines efficient incremental synchronization with rsync, portable archives with tar, and consistent snapshots without downtime. This guide shows how these tools, together with the 3-2-1 rule, add up to a resilient strategy for a small server fleet, including the restore tests that are the only thing that truly verifies a backup.

An offsite backup is the copy that survives a fire, theft, or ransomware infection at the local site. The 3-2-1 rule gives a simple but effective formula for this: three copies of the data, on two different media types, at least one physically separated from the main site. This article shows how to implement that rule on Linux servers in an automated, encrypted, and monitored way.