LINUX SYSADMIN COMMANDS ( WORKSTATION / SERVER )

All commands tested on Ubuntu Server.
Some of the commands may, or may not work, or be useful in desktop enviroment.

Please use these tools with caution, data loss can happen.
use -h or -help if necessary.

( Example: [interface] = eth0 or ens33 )

( Example: [ip address] = 192.168.2.1 )

( Example: [ip address range/subnetmask] = 192.168.2.0/24 )

( Example: [command name] = vsftp )

( Example: [sec] = seconds )

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USEFUL COMMANDS

command	description
sudo ifconfig	# Basic networking information
sudo dpkg --list	# List all installed packages on the system
sudo nmap [ip address]	# Display open ports
sudo bmon	# Watch network traffic in realtime
sudo iftop	# Watch network traffic in realtime
sudo tcpdump -i [interface]	# Watch network traffic in realtime from your interface
# Example: Track traffic on network's device with it's ip address: sudo tcpdump -i [host interface] host [target ip address] # Example: Track network traffic: sudo tcpdump -i [host interface] net [network ip address/subnet] ( Example of network address with subnet mask (class C): 192.168.2.0/24 )
sudo dhclient [interface]	# Renew dynamic addresses
sudo dstat	# Recource monitor
sudo tshark -i [interface]	# Capture network packets (Terminal version of wireshark)
sudo ethtool [interface]	# Info of network device
sudo ip addr add [ip address/subnet mask] dev [interface]	# Temporary assign static ip address
sudo ip link set dev [interface] up	# The ip can then be used to set the link up
sudo ip link set dev [interface] down	# The ip can then be used to set the link down
sudo ip route add default via [ip address]	# Set default gateway address
sudo ip route show	# Show default gateway
sudo ip addr flush [interface]	# Reset network configuration
sudo /etc/init.d/networking restart	# Start with new configuration
sudo service vsftpd start	# Start vsftpd
sudo ufw status verbose	# Enable UFW and check its status
sudo ufw reload	# Restart ufw
sudo smbstatus	# Check is samba active
sudo service --status-all	# Show services installed
sudo service [service name] start	# Start service
sudo apt install open-vm-tools	# Install vmware tools terminal
sudo ip a	# To quickly identify all available Ethernet interfaces
sudo ip addr add [ip address/subnet mask] [interface]	# To temporarily configure an IP address
sudo apt install ubuntu-mate-core	# Install desktop on server
sudo apt install ne	# Install ne text editor, vim alternative
sudo nautilus	# Access the filesystem with full priviledges with default gnome file manager gui
sudo aptitude	# Text based manager for installing software
sudo atop	# System and process monitor
sudo iotop	# Linux I/O monitor
sudo powertop	# Power management monitor
sudo ifstat -i[interface] [sec]	# Network usage statistics

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# here is a example network configuration file used by netplan to put static address:
# configuration file can be found at: /etc/netplan

network:
version: 2
renderer: networkd
ethernets:
[interface]:
dhcp4: no
addresses: [host ip address/subnet mask]
gateway4: [default gateway ip address]
nameservers:
addresses: [dns ip address,sec dns ip address]

# here is a example network configuration file used by netplan to put dynamic address:
# configuration file can be found at: /etc/netplan

network:
version: 2
renderer: networkd
ethernets:
[interface]:
dhcp4: true

---

# Wireshark network monitors capture filters:

Capture traffic from a range of IP addresses:
net 192.168.2.0/24

capture ip:
host 192.168.2.1

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Sysadmin app's for linux:

Terminal emulator: tilix

terminal recource monitor: bashtop

Network sniffer: wireshark

Terminal effect: cmatrix

Linux full Office suite: libre office

Media player: vlc

Archive manager with GUI: peazip

Email software: thunderbird

Code editor: Visual Studio Code

Alternative to firefox: chromium

Nmap GUI: nmapsi4

Disk encryption: zulucrypt

Software packgace installer: gdebi

Software packgace manager: synaptic

Disk partition manager: gnome disks

Samba GUI: smb4k

Task manager: stacer

TOR connection system: anonsurf

TOR surfing: TOR browser

A graphical network monitor: etherape

Well-known FireWall ports:
Port	TCP	UDP	Name	Description
1	✓	✓	tcpmux	TCP port multiplexer
5	✓	✓	rje	Remote job entry
7	✓	✓	echo	Echo service
9	✓	✓	discard	Zero service for test purposes
11	✓	✓	systat	System information
13	✓	✓	daytime	Time and date
17	✓	✓	qotd	Sends quote of the day
18	✓	✓	msp	Sends text messages
19	✓	✓	chargen	Sends an infinite character string
20	✓		ftp-data	FTP data transfer
21	✓	✓	ftp	FTP connection
22	✓	✓	ssh	Secure Shell Service
23	✓		telnet	Telnet service
25	✓		smtp	Simple Mail Transfer Protocol
37	✓	✓	time	Machine-readable time protocol
39	✓	✓	rlp	Resource location protocol
42	✓	✓	nameserver	Name service
43	✓		nicname	WHOIS directory service
49	✓	✓	tacacs	Terminal access controller access control system
50	✓	✓	re-mail-ck	Remote mail checking
53	✓	✓	domain	DNS name resolver
67		✓	bootps	Bootstrap protocol services
68		✓	bootpc	Bootstrap client
69		✓	tftp	Trivial file transfer protocol
70	✓		gopher	Document search
71	✓		genius	Genius protocol
79	✓		finger	Delivers user contact information
80	✓		http	Hypertext transfer protocol
81	✓		Torpark:	Onion routing (unofficial)
82		✓	Torpark:	Control (unofficial)
88	✓	✓	kerberos	Network authentication system
101	✓		hostname	NIC host name
102	✓		Iso-tsap	ISO TSAP protocol
105	✓	✓	csnet-ns	Mailbox mail server
107	✓		rtelnet	Remote telnet
109	✓		pop2	Post office protocol v2 for e-mail communication
110	✓		pop3	Post office protocol v3 for e-mail communication
111	✓	✓	sunrpc	RPC protocol for NFS
113		✓	auth	Authentication service
115	✓		sftp	Simple file transfer protocol
117	✓		uucp-path	File transfer between Unix systems
119	✓		nntp	Transfer of messages in news groups
123		✓	ntp	Time synchronization service
137	✓	✓	netbios-ns	NETBIOS name service
138	✓	✓	netbios-dgm	NETBIOS datagram service
139	✓	✓	netbios-ssn	NETBIOS session service
143	✓	✓	imap	Internet message access protocol for e-mail communication
161		✓	snmp	Simple network management protocol
162	✓	✓	snmptrap	Simple network management protocol trap
177	✓	✓	xdmcp	X display manager
179	✓		bgp	Border gateway protocol
194	✓	✓	irc	Internet relay chat
199	✓	✓	smux	SNMP UNIX multiplexer
201	✓	✓	at-rtmp	AppleTalk routing
209	✓	✓	qmtp	Quick mail transfer protocol
210	✓	✓	z39.50	Bibliographic information system
213	✓	✓	ipx	Internetwork packet exchange
220	✓	✓	imap3	IMAP v3 for e-mail communication
369	✓	✓	rpc2portmap	Coda file system port mapper
370	✓	✓	codaauth2	Coda file system authentication service
389	✓	✓	ldap	Lightweight directory access protocol
427	✓	✓	svrloc	Service location protocol
443	✓		https	HTTPS (HTTP over SSL/TLS)
444	✓	✓	snpp	Simple network paging protocol
445	✓		microsoft-ds	SMB over TCP/IP

64	✓	✓	kpasswd	Kerberos password change
500		✓	isakmp	Security protocol
512		✓	exec	Remote process execution
512	✓		comsat/biff	Mail client and server
513	✓		login	Login to remote computer
513	✓		who	Whod user logging daemon
514	✓		shell	Remote shell
514		✓	syslog	Unix system logging service
515	✓		printer	Line printer daemon print services
517		✓	talk	Talk remote calling
518		✓	ntalk	Network talk
520		✓	efs	Extended file name server
520		✓	router	Routing information protocol
521		✓	ripng	Routing information protocol for IPv6
525		✓	timed	Time server
530	✓	✓	courier	Courier remote procedure call
531	✓	✓	conference	Chat over AIM and IRC
532	✓		netnews	Netnews newsgroup service
533		✓	netwall	Emergency broadcasts
540	✓		uucp	Unix-to-Unix copy protocol
543	✓		klogin	Kerberos v5 remote login
544	✓		kshell	Kerberos v5 remote shell
546	✓	✓	dhcpv6-client	DHCP v6 client
547	✓	✓	dhcpv6-server	DHCP v6 server
548	✓		afpovertcp	Apple filing protocol over TCP
554	✓	✓	rtsp	Real time streaming protocol
556	✓		remotefs	Remote file system
563	✓	✓	nntps	NNTP over SSL/TLS
587	✓		submission	Message submission agent
631	✓	✓	ipp	Internet printing protocol
631	✓	✓		Common Unix printing system (unofficial)
636	✓	✓	ldaps	LDAP over SSL/TLS
674	✓		acap	Application configuration access protocol
694	✓	✓	ha-cluster	Heartbeat service
749	✓	✓	kerberos-adm	Kerberos v5 administration
750		✓	kerberos-iv	Kerberos v4 services
873	✓		rsync	rsync file transfer services
992	✓	✓	telnets	Telnet over SSL/TLS
993	✓		imaps	IMAP over SSL/TLS
995	✓		pop3s	POP3 over SSL/TLS

SUBNETTING (example in yellow):

number of subnets:	1	2	4	8	16	32	64	128	256
number of hosts per subnet:	256	128	64	32	16	8	4	2	1
subnet mask:	/24	/25	/26	/27	/28	/29	/30	/31	/32

example of original network ID: 192.168.4.0/26 ,with 4 subnets:
network ID:	subnet mask:	host ID range:	number of usable hosts:	broadcast ID:
192.168.4.0	/26	192.168.4.1 - 192.168.4.62	62	192.168.4.63
192.168.4.64	/26	192.168.4.65 - 192.168.4.126	62	192.168.4.127
192.168.4.128	/26	192.168.4.129 - 192.168.4.190	62	192.168.4.191
192.168.4.192	/26	192.168.4.193 - 192.168.4.254	62	192.168.4.255
subnet mask: 255.255.255.192 wildcard mask: 0.0.0.63 binary subnet mask: 11111111.11111111.11111111.11000000 IP / network class type: C CIDR notation: /26

Subnet masks:
CIDR subnet mask:	subnet mask:	binary subnet mask:
/24	255.255.255.0	11111111.11111111.11111111.00000000
/25	255.255.255.128	11111111.11111111.11111111.10000000
/26	255.255.255.192	11111111.11111111.11111111.11000000
/27	255.255.255.224	11111111.11111111.11111111.11100000
/28	255.255.255.240	11111111.11111111.11111111.11110000
/29	255.255.255.248	11111111.11111111.11111111.11111000
/30	255.255.255.252	11111111.11111111.11111111.11111100
/31	255.255.255.254	11111111.11111111.11111111.11111110
/32	255.255.255.255	11111111.11111111.11111111.11111111