Rohan Timalsina

nmcli is the command-line client for NetworkManager. It lists devices and connections, sets IPv4/IPv6 addresses, DNS, routes, hostname, and applies profile changes without editing ifcfg files by hand.

df reports free and used space on mounted file systems. du walks directories and sums how much disk space files and folders consume — use df for mount points, du to find what is filling a path.

dig and host query DNS name servers from the command line. dig exposes full resolver control and sectioned output; host prints concise answers for quick forward and reverse lookups.

gzip compresses single files with the DEFLATE algorithm, replacing each source with a .gz file by default. gunzip and zcat decompress; use -k to keep originals, -c to write to stdout, and -r for directory trees.

On systemd-based Linux, hostnamectl queries and changes the static, transient, and pretty hostnames plus chassis, icon, deployment, and location metadata. It talks to systemd-hostnamed and updates /etc/hostname where …

kill sends a signal to a process when you know its PID; pkill matches processes by name or command line and signals them in bulk. Together they are the standard way to stop runaway jobs, reload daemons, or end test …

timedatectl reads and sets the system clock, time zone, NTP synchronization, and RTC mode on systemd-based Linux. It talks to systemd-timedated and systemd-timesyncd for status and one-line changes without hand-editing …

Match lines with extended and Perl regex, pattern files, whole words, and context lines on files or stdin. This page covers pattern engines and line-level matching — not recursive directory walks.

mke2fs builds ext2, ext3, or ext4 filesystems on a block device or image file. It is the low-level formatter behind mkfs.ext4 and writes the superblock, inode tables, journal, and default mount metadata for …

losetup attaches regular files or block devices to /dev/loop* kernel nodes so you can partition, format, and mount disk images without dedicated hardware. It also lists, resizes, and detaches loop devices from the shell.

mdadm assembles, creates, monitors, and stops Linux MD RAID devices (md arrays) from partitions or whole disks. It writes version 1.2 metadata superblocks, reports array health, and integrates with /etc/mdadm/mdadm.conf …

pvcreate writes the LVM label and metadata on a disk or partition so it can join a volume group. Use it on empty block devices before vgcreate or vgextend.

vgcfgrestore rebuilds volume group metadata from text backups created by LVM — usually under /etc/lvm/archive and /etc/lvm/backup. It recovers mistyped lvremove or vgcfg changes; it does not replace disk imaging when …

lvscan lists logical volumes on the host with activation state, device path, size, and allocation policy. Use it for a quick inventory before lvdisplay or lvs.

lvdisplay prints detailed logical volume fields — path, UUID, size, extents, allocation, snapshot status, and device-mapper block major:minor. Use it when lvs is not enough.

lvreduce returns free extents from a logical volume to the volume group. Shrink the filesystem first on ext4 — data in the removed region is destroyed. Root LV shrink requires offline maintenance.

lvextend grows a logical volume by taking free extents from its volume group. The filesystem inside the LV must grow too — resize2fs for ext4, xfs_growfs for XFS — or df still shows the old size.

lvrename changes the name of a logical volume inside a volume group. The LV UUID and data stay the same — update fstab, boot loaders, and refresh device-mapper after renaming root or data volumes.

lvremove deletes logical volumes from a volume group and frees their extents. Unmount filesystems first — active or open LVs block removal unless you force.

lvchange activates or deactivates logical volumes and updates runtime attributes — read-only access, contiguous allocation, readahead, and metadata refresh after renames.

vgcreate groups one or more physical volumes into a volume group — the storage pool from which logical volumes are allocated. It can initialize PVs automatically if they are not already labeled.

lvcreate allocates logical volumes from free extents in a volume group. Create linear volumes, snapshots, and size-by-percentage LVs before you mkfs and mount.

parted creates and edits partition tables on disks and loop images — GPT or msdos labels, primary and logical partitions, resize, flags, and scripted one-liners. It is the GNU replacement for classic fdisk on large disks …

On RHEL 8+, Fedora, Rocky Linux, and AlmaLinux, dnf is the default RPM package manager. It installs and removes software from repositories, resolves dependencies with libsolv, and keeps a transaction history you can …

On RHEL 7, CentOS 7, and other legacy RPM systems, yum installs and removes packages from configured repositories. It resolves dependencies, supports package groups, and records transaction history for undo and rollback.

which reports the pathname of an executable that would run for a given command name, searching directories in PATH in order. It answers which file the shell would start — not whether that file exists on disk in general.

lzop compresses single files with the LZO algorithm and writes .lzo archives. It favors speed over the smallest possible size — useful when you need quick one-file compression without building a tar archive.

xz compresses single files into the .xz format using LZMA2. It replaces the original by default, supports integrity tests, preset levels, and pairs with tar for .tar.xz archives.

bzip2 compresses single files with the Burrows–Wheeler algorithm. By default it replaces the original with a .bz2 file; use -k to keep the source, or pipe to tar for directory archives.

apt-cache reads the local APT package index without network access. Use it to search package names, inspect versions and pinning policy, and trace forward or reverse dependencies before install or removal.