Linux Commands Quick Guide

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This Guide contains all the Linux commands that you may have to use for ThingWorx Analytics Installation or day to day use.

Command/Category	Description
Network/port
ip a	List the ips of all of the network interfaces
ssh	How to jump from one machine to another
ping	Send packets to a remote machine. useful for testing connectivity
netstat –anp	Check active port
cat < /dev/tcp/localhost/8080	Test connection to a port Replace localhost with desired hostname or ip, replace 8080 with desired port number (/dev/tcp/host/port)
exit	Exit my current sign in. this lets one disconnect from remove ssh sessions or if one has changed one's user e.g. switched to root
scp	Retrieve something via ssh
Resource Usage
free -m	Check memory -m is for output in Mb
Mpstat -P ALL	CPU usage
top	Process usage
jvmtop	Collect cpu usage of jvm and its thread https://github.com/patric-r/jvmtop (requires jdk to be installed)
File Interaction
cp / mv	Copy and move respectively. mv just deletes the source file. Usage: cp /source/location/file /output/location/file
cat	Mostly used to just print the contents of a file to the command line. can also print multiple files at once: cat /var/log/gridworker/warning.log /var/log/gridworker/error.log
vim / vi	A command line text editor. Not the most user friendly (none of them are) but really useful. Here's a cheat sheet for the commands https://www.fprintf.net/vimCheatSheet.html
rm	Remove files
chmod	Change the access permissions of files
chown	Change the user or group ownership of files
grep	A text based filtering. Useful for making a larger list smaller and more targeted. Almost always used after a pipe (see pipe below)
less	Generally used to view the contents of a file with more friendly scrolling
locate	Find a file by name
Directory
ls	What’s in the directory. Will do the current directory but you can also pass the directory e.g. ls /var/log/tomcat. Black writing is files Blue writing is directories Red writing is compressed file
pwd	Tell me which directory I'm currently in
cd	Change directory. provide the directory to change to or just use cd to return to the user's home directory
clear	Clears the screen Terminal clears all provided commands
mkdir	Creates Directories
Running Processes
ps	Query what services are running. usually use ps -aux to get a full, sorted list. using grep with this is helpful
systemctl	The correct way to interact with services that are running
Package installation
yum install <packageName>	Install a package. More useful commands: https://www.centos.org/docs/5/html/5.1/Deployment_Guide/s1-yum-useful-commands.html
yum list installed	List installed packages
yum list <package>	List available packages
yum --showduplicates list java-1.7.0-openjdk-devel	Use --showduplicates to see all versions Can use * for package name: openjdk
rpm -ql <packagename>	Find where package are installed Note: works if package installed with yum
Yumdownloader --urls <packageName>	Find URL where a package is downloaded from. Note: need to install yum-utils package
Repoquery --requires <packageName>	Find dependencies of a package Note: need to install yum-utils package
repoquery --qf=%{name} -g --list --grouppkgs=all [groups] \| xargs repotrack -a x86_64 -p /repos/Packages	Download a package with all its dependencies. Need to install yum-utils package From <http://unix.stackexchange.com/questions/50642/download-all-dependencies-with-yumdownloader-even-if-already-installed>
Other Commands
curl http://localhost:8080/1.0/about/versioninfo	Send REST call via command line Use -X POST (default GET) for a POST (see man page - https://curl.haxx.se/docs/manual.html for example) See also http://www.codingpedia.org/ama/how-to-test-a-rest-api-from-command-line-with-curl/
Find / -type f -exec grep -I mystring {} \;	Search string in files
Sudo -u user command	Execute a command as different user

The below helpers are not commands themselves, but can be used in conjunction with the above commands.

Helper	Description
'pipe'	The \| character. lets one chain commands. e.g. ps -aux \| grep java
./	The shorthand way to refer to this directory explicitly
../	The shorthand way to refer to the parent directory
'tab completion'	Pressing tab will let linux guess what command/option best fits what's currently written. very useful for navigating directories and long-named files (NOTE: not necessarily tab based upon one's keyboard layout/language)
'ctrl-r'	Look up the mostly likely command that matches what one typing. so if one earlier used ps -aux \| grep java \| less and the hit ctrl-r and typed -aux it would likely pull that command or at least the most recent one that matches