++++ man

man fdisk

fdisk - Partition table manipulator for Linux

SYNOPSIS
fdisk [-u] [-b sectorsize] [-C cyls] [-H heads] [-S sects] device

fdisk -l [-u] [device ...]

fdisk -s partition ...

fdisk -v

DESCRIPTION
Hard disks can be divided into one or more logical disks called parti‐
tions. This division is described in the partition table found in sec‐
tor 0 of the disk.

In the BSD world one talks about ‘disk slices’ and a ‘disklabel’.

Linux needs at least one partition, namely for its root file system.
It can use swap files and/or swap partitions, but the latter are more
efficient. So, usually one will want a second Linux partition dedicated
as swap partition. On Intel compatible hardware, the BIOS that boots
the system can often only access the first 1024 cylinders of the disk.

man nmap

NMAP(1) Nmap Reference Guide NMAP(1)

NAME
nmap - Network exploration tool and security / port scanner

SYNOPSIS
nmap [Scan Type...] [Options] {target specification}

DESCRIPTION
Nmap (“Network Mapper”) is an open source tool for network exploration
and security auditing. It was designed to rapidly scan large networks,
although it works fine against single hosts. Nmap uses raw IP packets
in novel ways to determine what hosts are available on the network,
what services (application name and version) those hosts are offering,
what operating systems (and OS versions) they are running, what type of
packet filters/firewalls are in use, and dozens of other
characteristics. While Nmap is commonly used for security audits, many
systems and network administrators find it useful for routine tasks
such as network inventory, managing service upgrade schedules, and
monitoring host or service uptime.