Nov 162015

Find the system host name

Display the system’s host name:
$ hostname
$ cat /etc/hostname

Display the system’s DNS domain name:
$ dnsdomainname

Display the system’s Fully Qualified Domain Name (FQDN):
$ hostname -f

Find the system serial number, manufacturer of the system and model name

$ sudo dmidecode -s system-serial-number
$ sudo dmidecode -s system-manufacturer
$ sudo dmidecode -s system-product-name
$ sudo dmidecode | more

OR use the lshw command:
# lshw | more
$ sudo lshw -short

Display information about installed hardware

$ sudo lsdev

Find the system CPU info

$ cat /proc/cpuinfo
$ lscpu

Display CPU (processors) related statistics

$ sudo mpstat
$ sudo mpstat 1
$ sudo mpstat -A

Find the system main memory (RAM) info

Show statistics about memory usage on the system including total installed and used RAM:
$ less /proc/meminfo
Show amount of free and used memory in the system:

## Display the amount of memory in megabytes ##
free -m
## Display the amount of memory in gigabytes ##
free -g
## Display the amount of memory in terabytes ##
free --tera
## Display human readable output ##
free -h

Show the system swap space usage

$ swapon -s
$ cat /proc/swaps
$ cat /proc/meminfo
$ top
$ vmstat
$ for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r | less
$ smem

Show the system virtual memory statistics

$ sudo vmstat
$ sudo vmstat 1
$ sudo vmstat 2

Find the Ubuntu Linux distribution version and related information

$ lsb_release -a

Find the system kernel version number

$ uname -r
$ uname -a

Find the system kernel parameters

$ cat /proc/cmdline
$ sysctl -a | more

Find the system kernel architecture (32 bit or 64 bit)

$ uname -m
$ getconf LONG_BIT
$ arch

Find the system disk information

Show all installed disks and size:
# fdisk -l | grep '^Disk /dev'

List all partitions of /dev/sda disk:

To read a disk label for /dev/sda:
# fdisk -l /dev/sda
To label a disk:
$ sudo fdisk /dev/sda
$ sudo e2label /dev/sda1
$ sudo cfdisk /dev/sda

Show block device attributes:

# blkid

List all block devices:

# lsblk

Display file system disk space usage:

$ df
$ df -H
$ df -HT

Estimate file space usage:

$ du
$ du /home

Display mounted file system:

$ cat /proc/mount
$ mount

Display SCSI devices (or hosts) and their attributes on Linux:

$ lsscsi

Display I/O statistics

$ sudo iostat
$ sudo iostat 2

Find the system PCI devices information

$ lspci
$ lspci -vt
$ lspci | grep -i 'something'
$ lspci -vvvn| less

Find the system USB devices information

$ lsusb
$ lsusb -vt

Find the system Wireless devices information

$ iwconfig
$ watch -n 1 cat /proc/net/wireless
$ wavemon

Find the system VGA/Graphics devices information

$ lspci | grep -i vga
$ lspci -vvnn | grep VGA

$ sudo lshw -class display

Find the system NVIDIA Graphics devices information

The following commands only works with Nvidia’s binary Linux driver:
$ nvidia-smi
$ nvidia-settings

Find the system AMD/ATI Graphics devices information

The following command only works with AMD’s binary Linux driver called catalyst:
$ fglrxinfo

Which version of Unity am I running?

$ unity --version

Find the system audio devices information

$ lspci | grep -i audio
$ cat /proc/asound/cards
$ arecord -l

Display the system/laptop battery status & thermal temperature

$ upower -i /org/freedesktop/UPower/devices/battery_BAT0
$ acpi -V

Find out how long the system has been running

$ uptime
$ who
$ w

Find the system load

$ uptime
$ cat /proc/loadavg
$ sudo top
$ sudo htop
$ sudo atop

Show the system reboot and shutdown history

$ last reboot
$ last shutdown

Show runlevel

$ runlevel
$ who -r

Display kernel ring buffer (boot time) messages

Use the following command to see boot time message including hardware configuration
$ sudo less /var/log/dmesg
$ sudo grep 'regx' /var/log/dmesg
$ sudo grep '[h|s]d' /var/log/dmesg

Display the system drivers (modules)

$ sudo lsmod
$ sudo modinfo {driver_name}
$ sudo modinfo kvm

Find the system IP address and related information

You need to use the ip command:

## Info about all interfaces. Must be run as root via sudo command ##
sudo ip a
sudo ip
sudo ip link ls up
sudo ifconfig -a
## Only show eth1 interface info ##
sudo ip a show eth0
sudo ifconfig eth0

Display the system routing table

## You can use any one of the following command ##
## Must be run as root ##
sudo ip r
sudo route -n
sudo netstat -nr

Display the system ethernet bridge

$ sudo brctl show
$ sudo bridge link

Display the system DNS server and related information

Display the system name server IP address (ISP or your dns server IP should be listed here):
# cat /etc/resolv.conf
Display the system resolver configuration file. This is useful to find out how host lookups are to be performed:
# cat /etc/host.conf
Use above two files to configure name resolution.

Display information about the system ports and socket

## Must run as root via sudo ##
sudo ss
## Display all listing ports ##
sudo ss -l
sudo netstat -tulpn
sudo netstat -tulpn | grep LISTEN
## Display all TCP sockets
sudo ss -t -a
## Display all UDP sockets.
sudo ss -u -a
## List all open files
lsof | more
lsof | grep something
lsof /dev/sda2
lsof /path/to/file

Display the list of running services

### SYS V ###
$ sudo service --status-all

$ sudo initctl list

Find out if service is enabled:

$ sudo initctl status service-name
$ sudo initctl status smbd

## SYS V
$ sudo service serviceName status
$ sudo service nginx status

View log files

$ cd /var/log
$ ls -l
$ tail -f /var/log/fileName
$ grep 'something' /var/log/fileNameHere

Find file by name

$ locate fileName
$ locate htpasswd
$ locate passwd
$ locate my.resume.doc

Find file by given condition

$ find {/dir/to/search} -name {file-to-search} -print
$ find /etc/ -name /etc/passwd -print
$ find $HOME -name '*.doc' -print

View user account details

$ less /etc/passwd
$ grep userName /etc/passwd
$ getent passwd

View group account details

$ less /etc/group
$ getent group
$ grep group-name /etc/group
$ groups userName

View password policy

$ chage -l userName
$ chage -l root
$ chage -l vivek

View system usage

$ sudo top
$ sudo htop
$ sudo atop
$ sudo ps auxwww
$ sudo netstat [options]
$ sudo iostat
$ sudo mpstat 1
$ sudo sar [options]

Trace system call

$ strace -o output.txt /bin/foo
$ strace -p 22254 -s 80 -o debug.nginx.txt

Trace library call

$ sudo ltrace /usr/sbin/httpd
$ sudo ltrace /sbin/chroot /usr/sbin/httpd

View process info

$ sudo pstree
$ sudo pstree | less
$ sudo ps auxwwwm
$ ps alxwww
$ ps auxwww
$ lsof -b M -n -l

Change process priority

$ sudo /bin/nice -n -1 command-name-here
$ sudo /bin/nice -n -1 pid
$ sudo renice {priority} pid

View process’s CPU affinity

$ sudo taskset -p {pid-here}
$ sudo taskset -p 42

Display the system listing of all package installed

$ dpkg -l
$ dpkg -l | less
$ dpkg -l nginx

Display the system listing of all patches installed

$ sudo apt-show-versions -a | grep -i "security"

Display the list of needed runtime libraries to run file

$ ldd file

Find what package a file belongs to

$ dpkg -S /path/to/file
$ dpkg -S /bin/ls

Create a backup list of all installed software

$ sudo dpkg --get-selections > /root/installed.pkgs.txt
Want to restore it again?
$ sudo dpkg --set-selections < /root/installed.pkgs.txt

Display the system firewall configuration

$ sudo iptables -L -n -v
$ sudo ufw status numbered
$ sudo ufw status verbose
$ sudo ufw app list

Do not forget to read man pages featured in this post:
$ man dpkg
$ man htop
$ man ...

Finally, make a backup – it cannot be stressed enough how important it is to make a backup of your system. A good backup plan allow you to recover from disk failure, accidental file deletion, file corruption, or complete server destruction, including destruction of on-site backups.