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sysadmin (14)

WSL Interoperability

Running Linux tools from Windows and vice versa, file system access, and networking between WSL and Windows.
wsl linux windows interop networking sysadmin reference web-researched

apt-get Package Management

Debian and Ubuntu package management — update, install, remove, upgrade, and maintain packages with apt-get.
apt debian ubuntu packages package-management dpkg sources ppa gpg sysadmin web-researched

df, du & duf — Disk Usage

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.
df du duf dust ncdu gdu disk filesystem storage cli web-researched

htop — Interactive Process Viewer

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.
htop cli sysadmin monitoring processes web-researched

ip — iproute2 Networking

Modern replacement for ifconfig, route, and arp. Inspect and configure interfaces, addresses, routes, neighbour tables, and network namespaces with the iproute2 ip command.
ip iproute2 networking sysadmin cli routing web-researched

journalctl — systemd Journal Query

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.
journalctl cli sysadmin logs systemd observability web-researched

lsof & ss — Open Files and Sockets

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.
lsof ss lsfd sockets networking processes debug cli sysadmin web-researched

ps, ss & netstat — Processes & Sockets

Inspect running processes (ps), list network connections and listening ports (ss / netstat). Covers output formats, filtering, process trees, and socket state analysis.
ps netstat ss processes networking sockets cli sysadmin web-researched

systemd Unit Files

Writing, enabling, and managing systemd service, timer, and socket units.
systemd linux services daemons timers sockets sandboxing sysadmin web-researched

Filesystems — Inodes, Links, Journaling, ext4/XFS/Btrfs/ZFS/APFS/NTFS

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.
filesystem inode ext4 xfs btrfs zfs apfs ntfs mount journaling links storage

Memory Management — Virtual Memory, Paging, Swap, OOM, mmap

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.
memory virtual-memory paging swap oom mmap page-cache jemalloc mimalloc sysadmin

Networking Stack — OSI/TCP-IP, Sockets, TCP/UDP, MTU, NAT, DNS

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.
networking osi tcp-ip sockets tcp udp mtu nat routing dns sysadmin

Processes — Fork, Exec, Signals, Zombies, Cgroups

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.
process fork exec signal zombie orphan pid pgid sid cgroup sysadmin

Security Fundamentals — Users, Permissions, Capabilities, MAC, Sandboxing

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.
security users groups permissions capabilities suid sgid selinux apparmor sandbox encryption mac sysadmin