Change the Hostname on Linux with hostnamectl (Permanently)
Set a permanent hostname with hostnamectl on Ubuntu, Debian and RHEL, update /etc/hosts, fix unable to resolve host, and stop cloud-init reverting it.
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Linux
Linux server administration: Debian, Ubuntu, AlmaLinux, storage, performance and troubleshooting.
SSH Agent and Agent Forwarding: Use Your Keys Securely
Use ssh-agent to unlock keys once, add keys with ssh-add, forward your agent for git pulls, understand the risks, and use safer options like ProxyJump.
NUMA on Linux Servers: What It Is and When It Matters
NUMA for server admins: nodes and memory locality, checking topology with lscpu and numactl, effects on databases, pinning and interleaving, and VPS notes.
Linux OOM Killer: Why Processes Die and How to Prevent It
Why MySQL or Node was killed: read OOM killer logs, understand oom_score, protect services, cap memory with systemd, add swap, right-size the server.
sysctl Tuning on Linux: Network and Memory Settings That Matter
Change kernel parameters with sysctl: persistent files in /etc/sysctl.d, swappiness, BBR, somaxconn, conntrack, ip_forward, and what not to tweak.
systemd-resolved Explained: 127.0.0.53, resolvectl and DNS Fixes
How systemd-resolved handles DNS: the 127.0.0.53 stub, resolvectl, setting DNS servers, DNS over TLS, flushing the cache, port 53 conflicts, and fixes.
ps Command in Linux: List and Inspect Processes
Use ps to list processes: ps aux vs ps -ef, custom columns, sorting by CPU or memory, process trees, threads, finding PIDs and reading process states.
Fix "Too Many Open Files": ulimit and LimitNOFILE on Linux
Fix Too many open files: check limits with ulimit and /proc, raise them for users and with LimitNOFILE for systemd services, tune Nginx and MySQL.
Linux ACLs: setfacl and getfacl for Fine-Grained Permissions
Use POSIX ACLs to give extra users or groups access without changing ownership: setfacl and getfacl, default ACLs, the mask, backups, and web server examples.
Linux Load Average Explained: What uptime Numbers Mean
What Linux load average means: the 1, 5 and 15 minute values, comparing load to CPU cores, I/O wait, steal time on a VPS, and what to do when it is high.
Nano Editor Guide: Shortcuts and Tips for Server Admins
Edit files on Linux with nano: open, save and exit, search and replace, cut and paste lines, go to a line, syntax highlighting, backups and a handy nanorc.
Set the Timezone on Linux with timedatectl (Ubuntu, Debian)
Check and change the server time zone with timedatectl, choose UTC or local time, set the zone for PHP, MySQL, cron and Docker, and verify time sync.
Linux File System Caching: Page Cache, Dentry and Inode Caches
How Linux caches file data and metadata (page, dentry and inode caches), how to see what is cached, and the vfs_cache_pressure setting.
How to Customize Your Bash Prompt (PS1)
Customize the Bash prompt with PS1: escape sequences, colours, Git branch, exit status, a red root prompt, and making changes permanent.
Linux Disk Caching Explained: Page Cache, Dirty Pages, fsync
How Linux caches reads and buffers writes in RAM, why free memory looks low, how dirty pages are flushed, and what fsync guarantees.
mount Command in Linux: Mount Disks, Images and Shares
Mount and unmount filesystems: disks, options like noexec and ro, bind mounts, ISO files, NFS and SMB shares, findmnt, and fixing target is busy.
du Command: Check Directory Sizes and Disk Usage on Linux
Use du to see how much space directories use: human-readable sizes, depth limits, sorting, excluding paths, apparent size, and ncdu for interactive browsing.
mkdir Command in Linux: Create Directories (with -p and -m)
Create directories with mkdir: nested paths with -p, permissions with -m, brace expansion for project trees, ownership, and fixing common mkdir errors.
LVM on Linux: Physical Volumes, Volume Groups, Logical Volumes
Learn LVM step by step: create PVs, VGs and LVs, format and mount them, add disks to grow storage, use LVM snapshots for backups, and pvs/vgs/lvs.
Linux Kernel Modules: lsmod, modprobe, Blacklisting, Boot Loading
Manage Linux kernel modules: lsmod, modinfo, modprobe, loading at boot, module options, blacklisting, DKMS, and common VPS cases like WireGuard and BBR.
grep Command in Linux: 25 Examples You Will Use
Learn grep with practical examples: search files and directories, ignore case, invert matches, count, show context, regular expressions and log searching.
rclone Guide: Sync a Server With S3, B2, Google Drive and More
Use rclone to sync a Linux server with S3, B2, Google Drive and more: remotes, copy vs sync, crypt encryption, bandwidth limits, mounts, backups.
CentOS 7 End of Life: Migration Options for Your Server
CentOS 7 reached end of life in June 2024. Compare migration paths: AlmaLinux or Rocky via ELevate, CentOS Stream, Ubuntu or Debian, and a safe plan.
ss Command (netstat Replacement): Inspect Linux Sockets
Use ss to list listening ports, established connections and socket states, filter by port and address, count connections and map netstat commands to ss.