sysadmin
14 pages in this category.
WSL Interoperability
Running Linux tools from Windows and vice versa, file system access, and networking between WSL and Windows.
systemd Unit Files
Writing, enabling, and managing systemd service, timer, and socket units.
Security Fundamentals
OS-level security primitives every operator should know: users and groups, file permissions, Linux capabilities, SUID/SGID, mandatory access control (SELinux, AppArmor), sandboxing concepts, least privilege, and encryption at rest vs in transit.
ps, ss & netstat
Inspect running processes (ps), list network connections and listening ports (ss / netstat). Covers output formats, filtering, process trees, and socket state analysis.
Processes
Process lifecycle on Unix: fork/exec/wait, PIDs, signals, zombies and orphans, parent/child trees, process groups, sessions, controlling terminals, and a tour of Linux cgroups.
Networking Stack
How packets actually move: the OSI and TCP/IP layer models, the BSD socket API, TCP vs UDP, the three-way handshake, MTU/MSS, NAT and port translation, basic IP routing, and the full DNS resolution flow.
Memory Management
How operating systems give every process its own address space: virtual memory and paging, swap, the OOM killer, mmap, copy-on-write, the page cache, allocator choices (glibc, jemalloc, mimalloc), and how to read memory counters in top, ps, and free.
lsof & ss
Diagnose what's holding a port, which files a process has open, and the state of every TCP/UDP socket using lsof and the modern iproute2 ss utility.
journalctl
Query and follow systemd's structured journal. Covers unit filters, time ranges, priority levels, boot logs, namespaces, invocations, output formats, persistence, configuration, and disk-vacuum.
ip
Modern replacement for ifconfig, route, and arp. Inspect and configure interfaces, addresses, routes, neighbour tables, and network namespaces with the iproute2 ip command.
htop
Interactive process and resource monitor for the terminal. Covers function keys, sorting, filtering, signal sending, tree view, threads, and how to read load averages and memory correctly. Compares with top, btop, and bottom.
Filesystems
Core filesystem concepts every operator should know: inodes, directory structure, hard vs symbolic links, journaling, copy-on-write, and a head-to-head of ext4, XFS, Btrfs, ZFS, APFS, and NTFS with mount options and pitfalls.
df, du & duf
Check filesystem free space (df), measure directory sizes (du), and view a colourful disk overview (duf). Covers all key flags, human-readable output, modern alternatives (dust, gdu, ncdu), and common sysadmin recipes.
apt-get Package Management
Debian and Ubuntu package management — update, install, remove, upgrade, and maintain packages with apt-get.