diff --git a/docs/course/glossary.md b/docs/course/glossary.md index 9e496b8..2fbb5c2 100644 --- a/docs/course/glossary.md +++ b/docs/course/glossary.md @@ -1,25 +1,105 @@ # Glossary -**Apt**: Debian and Ubuntu package-management tooling. +Use this glossary as a quick lookup while working through the lessons and labs. The definitions favor practical Linux operations over academic precision. + +**ACL**: Access control list. An extension to traditional Unix permissions that can grant or deny access for specific users or groups. + +**Apt**: Debian and Ubuntu package-management tooling used to install, update, remove, and inspect software packages. + +**BIND**: A common DNS server implementation used to host authoritative zones and recursive resolvers. + +**Bootloader**: The program that starts an operating system kernel. GRUB is the most common Linux bootloader. + +**CIDR**: Classless inter-domain routing notation such as `192.0.2.0/24`, used to describe IP networks and address ranges. + +**CI/CD**: Continuous integration and continuous delivery or deployment. The practice of building, testing, and shipping changes through repeatable pipelines. **Daemon**: A background process that provides a service. -**Dnf**: Modern Fedora, Rocky Linux, AlmaLinux, and RHEL-family package-management tooling. +**Default gateway**: The router a host uses when traffic is destined for a network that is not directly connected. + +**Dnf**: Modern Fedora, Rocky Linux, AlmaLinux, and RHEL-family package-management tooling used to install, update, remove, and inspect software packages. + +**DNS**: Domain Name System. The distributed naming system that maps names such as `example.com` to records such as IP addresses, mail exchangers, and service metadata. + +**FQDN**: Fully qualified domain name, such as `www.example.com`, that identifies a host or service within the DNS hierarchy. **Filesystem**: The structure an operating system uses to store and retrieve files. +**Firewall**: Software or hardware that filters network traffic according to rules. Linux labs commonly use tools such as `nftables`, `firewalld`, or `ufw`. + +**GRUB**: Grand Unified Bootloader. A bootloader used by many Linux distributions to choose and start kernels. + +**Idempotent**: Safe to apply repeatedly with the same intended result. Configuration-management tools aim for idempotent changes. + +**Init system**: The first user-space process and service manager. On most current Linux distributions, this is systemd. + +**Inode**: Filesystem metadata that tracks a file's ownership, permissions, timestamps, size, and data-block locations. + +**IP address**: A numeric network address assigned to an interface. IPv4 examples look like `192.0.2.10`; IPv6 examples look like `2001:db8::10`. + **Journal**: The systemd logging system queried with `journalctl`. **Kernel**: The core of the operating system that manages hardware, processes, memory, and system calls. **Least privilege**: The practice of granting only the access needed to do a task. +**Load average**: A summary of runnable and waiting work on a system over 1, 5, and 15 minutes. Interpret it with CPU count and workload context. + +**LVM**: Logical Volume Manager. A Linux storage layer that can group disks, create flexible logical volumes, and resize storage more easily than raw partitions. + +**Mount point**: The directory where a filesystem is attached to the running file tree. + +**NAT**: Network address translation. A technique that rewrites packet addresses, commonly used for private networks that share public connectivity. + +**NFS**: Network File System. A Unix-oriented protocol for sharing filesystems over a network. + +**Package repository**: A trusted source of installable software packages and metadata for tools such as `apt` and `dnf`. + +**PATH**: The shell variable that lists directories searched when you run a command without typing its full path. + +**PID**: Process identifier. A numeric ID assigned to a running process. + +**Pipeline**: A shell pattern that connects one command's output to another command's input with `|`, or a CI/CD workflow that moves changes through build, test, and deploy stages. + +**Port**: A numeric endpoint used by TCP or UDP services. For example, SSH commonly listens on TCP port 22. + +**RAID**: Redundant array of independent disks. A storage technique that combines disks for redundancy, performance, or both. + +**Resolver**: The client-side or server-side DNS component that looks up DNS records on behalf of applications or users. + +**Rollback**: A planned way to return a system to a known-good state after a change fails or produces unexpected behavior. + **Runbook**: A written operational procedure for performing or recovering a task. **Service unit**: A systemd configuration object that controls a daemon or service. **Shell**: A command interpreter such as Bash or Zsh. +**Signal**: A process-control notification such as `SIGTERM` or `SIGKILL`. Signals are used to request process shutdown, reload, stop, or other behavior. + +**SLA**: Service-level agreement. A formal or informal promise about service behavior such as availability, response time, or support handling. + +**SMB**: Server Message Block. A file-sharing protocol commonly used by Windows systems and implemented on Unix-like systems with Samba. + **Snapshot**: A saved VM or storage state that can be restored after a mistake. +**SSH**: Secure Shell. The standard encrypted remote-login and remote-command protocol for Linux administration. + +**Sudo**: A tool that lets authorized users run specific commands with elevated privileges while preserving accountability. + +**Swap**: Disk-backed space the kernel can use when memory pressure is high. Swap is slower than RAM and should be interpreted as a symptom source during performance analysis. + +**systemd**: A Linux init system and service manager that also provides logging, timers, sockets, and unit dependency management. + +**Tarball**: An archive file, often ending in `.tar`, `.tar.gz`, or `.tgz`, used to bundle files for transfer or backup. + **TTL**: Time to live; in DNS, the cache duration for a record. + +**Unit file**: A systemd configuration file that describes a service, timer, socket, mount, or other managed object. + +**Virtual machine**: A complete guest operating system running on virtualized hardware provided by a hypervisor. + +**Volume**: A storage object presented to a system or application. Depending on context, it may refer to a disk, partition, logical volume, filesystem, container volume, or cloud block device. + +**Zone file**: A DNS data file that defines records for a domain or reverse-lookup zone.