LPIC-2 201-450 key terms

A sysstat tool that samples and records CPU, memory, disk, and network activity, keeping daily history files so you can compare current performance with earlier baselines.

Reports per-device and per-partition I/O throughput, average request queue length, and CPU utilization, which helps you identify a disk that has become the bottleneck.

Prints a compact table of processes, memory, swap, paging, block I/O, interrupts, and CPU time; the run-queue and paging columns expose memory pressure and CPU saturation.

The one-, five-, and fifteen-minute averages of tasks that are runnable or blocked in uninterruptible sleep, so processes waiting on slow disks also raise the figure.

Shows total, used, free, shared, buffer, and cache memory; the available column is the realistic number for judging whether a host needs more RAM.

An object file ending in .ko that can be inserted into or removed from a running kernel, adding drivers or features without rebooting the machine.

Loads or unloads kernel modules by name, resolves their dependencies from modules.dep, and applies options and blacklists configured under /etc/modprobe.d.

Scans the installed modules and writes modules.dep and modules.alias so that modprobe can locate modules and load them in the correct order.

A compressed cpio archive loaded alongside the kernel that supplies early userspace tools and storage drivers needed to find and mount the real root filesystem.

Generates an initramfs on Red Hat family systems by collecting the kernel modules and utilities required by the host's storage, filesystem, and network configuration.

Reads or changes kernel parameters at runtime, such as net.ipv4.ip_forward; persistent values are stored in /etc/sysctl.conf or files under /etc/sysctl.d.

The bootloader used by most distributions; it loads its configuration and modules from /boot/grub, shows a menu, and then starts the selected kernel.

The generated GRUB 2 menu file, usually found at /boot/grub/grub.cfg or /boot/grub2/grub.cfg, which should be rebuilt rather than edited by hand.

Scans /etc/default/grub and the scripts in /etc/grub.d and writes a new grub.cfg; the update-grub command on Debian systems wraps it.

A configuration file describing something systemd manages, such as a service, mount, socket, timer, or target, usually placed in /etc/systemd/system.

A unit that groups other units into a boot state, replacing traditional runlevels; multi-user.target is the normal text login and graphical.target adds a display manager.

The main command for controlling systemd: it starts, stops, enables, disables, masks, and inspects units, and reports whether a service has failed.

Queries the systemd journal, which stores structured messages from the kernel and services; filters select a unit, boot, priority, or time range.

The table of filesystems mounted at boot, with one line per entry giving the device, mount point, filesystem type, options, dump flag, and fsck pass order.

An identifier written into a filesystem when it is created; because it does not change when disks are added or reordered, fstab entries use it instead of device names.

Lists block devices together with their UUIDs, labels, and filesystem types by reading their superblocks, which makes it the quick way to build fstab entries.

Checks and repairs a filesystem; it must run while the filesystem is unmounted or mounted read-only, and the fstab pass number controls boot-time ordering.

An independently mountable and snapshot-able tree inside a Btrfs filesystem; subvolumes share the filesystem's free space and can carry their own mount options.

Disk space used as virtual memory when RAM runs short; it is activated with swapon and recorded in fstab with a swap entry, or provided by a swap file.

A storage layer that combines physical devices into volume groups and allocates logical volumes from them, so space can be resized without repartitioning disks.

A disk or partition initialized with pvcreate so LVM can use it; its metadata records which volume group it belongs to and how extents are allocated.

The pool of extents created from one or more physical volumes; logical volumes are carved out of this pool and can span the underlying disks.

A block device allocated from a volume group's free extents; it is formatted like a partition and often can be grown while the filesystem is mounted.

A copy-on-write view of a logical volume that preserves the original blocks as they are changed, typically used to take a consistent backup before a risky upgrade.

The tool for creating, assembling, monitoring, and inspecting Linux software RAID arrays, which appear as /dev/md devices made of member partitions or disks.

The iproute2 utility for inspecting and changing addresses, links, routes, and neighbor entries; it replaces ifconfig, route, and arp on current distributions.

A daemon that manages network devices and connection profiles, reacting to link changes; it is controlled graphically, through nmtui, or with the nmcli command.

A kernel driver that combines several network interfaces into one logical link for redundancy or increased throughput, using modes such as active-backup or 802.3ad.

A virtual layer-2 switch that joins physical and virtual interfaces into one broadcast domain, commonly used to attach virtual machines to the host's network.

The kernel's list of destination networks, each with a next-hop gateway, outgoing interface, and metric, consulted to choose where every packet is sent.

A scheduled utility that rotates, compresses, mails, and deletes log files according to rules in /etc/logrotate.conf and the files under /etc/logrotate.d.

A syslog daemon that receives messages from local services and remote hosts and writes them to files, databases, or forwarding destinations based on its rules.

A daemon that runs commands at fixed times from user crontabs and system files such as /etc/crontab and /etc/cron.d, with output normally mailed to the owner.

A unit pair that starts a service on a calendar or monotonic schedule, offering dependency handling and journal logging that plain cron jobs lack.

Copies files locally or over a remote shell, transferring only the differences by default; archive mode preserves permissions, ownership, timestamps, and symlinks.