Commands
Large Linux resource.
Vim
Copying and Pasting
Paste
First:
:set paste
Then enter insert mode. You will see the status bar insert (paste). Paste your code. ESC to exit out of that mode.
Then, lastly:
:set nopaste
Services
To check the status of a specific service:
service service_name status
To check the status of all services on the system:
service --status-all
To start, restart, stop, services:
service service_name stop
service service_name start
service service_name restart
Compressing
Zipping a file:
gzip -k filename
Run command replacing text with lines from file
The first step was to create a file which had a list of the names required. From this, a number of commands were used to edit this file in order to run it on the Linux system. The first step is to make sure that the file is saved as a LF line ending, as opposed to a CRLF ending. If this is not the case, Linux will see ^M characters at the end of each line in the file, this means that it cannot be run by bash. The next step is to add the “delete metric” code to each line. It appears as if the original file with the list of metrics must have a file extension (eg. *.txt)
This is done with the use of:
awk '{print "text placed in front of each entry" $1}' Original.txt > Final.sh
Where Original is the name of the file that is being augmented. Once this has happened, the file needs to be given execution permission:
sudo chmod +x Final.sh
Now the script can be executed on the server, this will run each line as a command.
Copying
Secure Copy
The scp command will always overwrite any previous files that were previously there before.
pscp -r 'C:\...' username@tsdb.eie.wits.ac.za:'/home/labproj/.../'
Count Files in Folder
ls -1 | wc -l
Size
Size of files in directory
Lists the size of files with the current directory.
ls -l *
Size of Folder
Outputs the size of the folder selected.
du -sh file_path
Size of Files and Folders in CWD
du -sk ./* | sort -nr | \
awk 'BEGIN{ pref[1]="K"; pref[2]="M"; pref[3]="G";} \
{ total = total + $1; x = $1; y = 1; \
while( x > 1024 ) { x = (x + 1023)/1024; y++; } \
printf("%g%s\t%s\n",int(x*10)/10,pref[y],$2); } \
END { y = 1; while( total > 1024 ) { total = (total + 1023)/1024; y++; } \
printf("Total: %g%s\n",int(total*10)/10,pref[y]); }'
Getting a Shell Script to Work
First create the shell script with:
touch filename.sh
Then edit the file with the contents you want. You have to allow it to have execution ability, you can do this by using
chmod +x filename.sh
Then you can run the script with
./filename.sh
Where the ‘./’ indicates that you are running it from inside the current folder.
Run command and keep it running even when user logs out
Use the screen package. This will run the command, and the user can leave that session with it will running. You can launch a screen by the simply command:
screen
Once the screen is up and running, you can issue your normal commands.
You can disconnect from the screen by using:
Ctrl + A followed by d
To go back into your screen:
screen -r
In order to close the screen one can use either:
exit or:
Ctrl + A followed by k
Killing another SSH Login
Search for the other login using: pstree -p
Kill the root process with: kill **
Where ** is the PID of the process you are attempting to kill
Delete all files that do not contain the *** file type
Deletes all files that are of a specific file type:
find . ! -name "*.file_fype" | xargs rm
Run specified command on multiple files
Finds all files with a specified extension (***), then runs a command on those files:
sudo find . -name "*.***" -exec "command here" {} \;
SSH Server
Bash:
ssh -L 13000:localhost:22 username@IP_Address
Using Python (this creates an SSH tunnel from Remote_Port to Local_Port):
python -m sshtunnel -U Username -P Password :Remote_Port -R
127.0.0.1:Local_Port -p 22 IP_Address
Rename Folder/File
mv oldName newName
Recursively replace text
The following grep command will recursively replace all occurrences of ‘foo’ with ‘bar’
egrep -lRZ 'foo' . | xargs -0 -l sed -i -e 's/foo/bar/g'
egrep -R is what enables the recursive search, and sed -i enables Sed’s ‘in-place’ mode to modify the files directly.
wget
Downloading from the internet, and other resources.
wget URL
Mirror the source directory and recursively dive into any directories found:
wget --mirror --recursive URL
OR
wget -m -r URL
wget -e robots=off -r -nc -mp URL
- -e robots=off: Navigates through all folders, even if the server doesn’t want it to.
- -nc or –no-clobber: Skip downloading duplicate files.
- -np or –n-parent: Stops wget from ascending into a parent directory.
- -accept: Accept only file types that you are looking for.
- –level=: Select the number of folder levels in which to go down. (–level=0 does not specify a level, so it will keep going)
- –reject: Ignore specified file types
Recursively loop through folders A through F and only get the text files:
FOR %g IN (A B C D E F) DO wget -e robots=off -r --level=0 -nc -np --accept txt URL
Big
Table of Contents
- Basic Operations
1.1. File Operations
1.2. Text Operations
1.3. Directory Operations
1.4. SSH, System Info & Network Operations
1.5. Process Monitoring Operations - Basic Shell Programming
2.1. Variables
2.2. Array
2.3. String Substitution
2.4. Functions
2.5. Conditionals
2.6. Loops - Tricks
- Debugging
1. Basic Operations
a. export
Displays all environment variables. If you want to get details of a specific variable, use echo $VARIABLE_NAME.
export
Example:
$ export
AWS_HOME=/Users/adnanadnan/.aws
LANG=en_US.UTF-8
LC_CTYPE=en_US.UTF-8
LESS=-R
$ echo $AWS_HOME
/Users/adnanadnan/.aws
b. whatis
whatis shows description for user commands, system calls, library functions, and others in manual pages
whatis something
Example:
$ whatis bash
bash (1) - GNU Bourne-Again SHell
c. whereis
whereis searches for executables, source files, and manual pages using a database built by system automatically.
whereis name
Example:
$ whereis php
/usr/bin/php
d. which
which searches for executables in the directories specified by the environment variable PATH. This command will print the full path of the executable(s).
which program_name
Example:
$ which php
/c/xampp/php/php
e. clear
Clears content on window.
1.1. File Operations
| cat | chmod | chown | cp | diff | file | find | gunzip | gzcat | gzip | head |
| lpq | lpr | lprm | ls | more | mv | rm | tail | touch |
a. cat
It can be used for the following purposes under UNIX or Linux.
- Display text files on screen
- Copy text files
- Combine text files
- Create new text files
cat filename cat file1 file2 cat file1 file2 > newcombinedfile cat < file1 > file2 #copy file1 to file2
b. chmod
The chmod command stands for “change mode” and allows you to change the read, write, and execute permissions on your files and folders. For more information on this command check this link.
chmod -options filename
c. chown
The chown command stands for “change owner”, and allows you to change the owner of a given file or folder, which can be a user and a group. Basic usage is simple forward first comes the user (owner), and then the group, delimited by a colon.
chown -options user:group filename
d. cp
Copies a file from one location to other.
cp filename1 filename2
Where filename1 is the source path to the file and filename2 is the destination path to the file.
e. diff
Compares files, and lists their differences.
diff filename1 filename2
f. file
Determine file type.
file filename
Example:
$ file index.html
index.html: HTML document, ASCII text
g. find
Find files in directory
find directory options pattern
Example:
$ find . -name README.md
$ find /home/user1 -name '*.png'
h. gunzip
Un-compresses files compressed by gzip.
gunzip filename
i. gzcat
Lets you look at gzipped file without actually having to gunzip it.
gzcat filename
j. gzip
Compresses files.
gzip filename
k. head
Outputs the first 10 lines of file
head filename
l. lpq
Check out the printer queue.
lpq
Example:
$ lpq
Rank Owner Job File(s) Total Size
active adnanad 59 demo 399360 bytes
1st adnanad 60 (stdin) 0 bytes
m. lpr
Print the file.
lpr filename
n. lprm
Remove something from the printer queue.
lprm jobnumber
o. ls
Lists your files. ls has many options: -l lists files in ‘long format’, which contains the exact size of the file, who owns the file, who has the right to look at it, and when it was last modified. -a lists all files, including hidden files. For more information on this command check this link.
ls option
Example:
$ ls -la rwxr-xr-x 33 adnan staff 1122 Mar 27 18:44 . drwxrwxrwx 60 adnan staff 2040 Mar 21 15:06 .. -rw-r--r--@ 1 adnan staff 14340 Mar 23 15:05 .DS_Store -rw-r--r-- 1 adnan staff 157 Mar 25 18:08 .bumpversion.cfg -rw-r--r-- 1 adnan staff 6515 Mar 25 18:08 .config.ini -rw-r--r-- 1 adnan staff 5805 Mar 27 18:44 .config.override.ini drwxr-xr-x 17 adnan staff 578 Mar 27 23:36 .git -rwxr-xr-x 1 adnan staff 2702 Mar 25 18:08 .gitignore
p. more
Shows the first part of a file (move with space and type q to quit).
more filename
q. mv
Moves a file from one location to other.
mv filename1 filename2
Where filename1 is the source path to the file and filename2 is the destination path to the file.
Also it can be used for rename a file.
mv old_name new_name
r. rm
Removes a file. Using this command on a directory gives you an error.
rm: directory: is a directory
To remove a directory you have to pass -r which will remove the content of the directory recursively. Optionally you can use -f flag to force the deletion i.e. without any confirmations etc.
rm filename
s. tail
Outputs the last 10 lines of file. Use -f to output appended data as the file grows.
tail filename
t. touch
Updates access and modification time stamps of your file. If it doesn’t exists, it’ll be created.
touch filename
Example:
$ touch trick.md
1.2. Text Operations
| awk | cut | echo | egrep | fgrep | fmt | grep | nl | sed | sort |
| tr | uniq | wc |
a. awk
awk is the most useful command for handling text files. It operates on an entire file line by line. By default it uses whitespace to separate the fields. The most common syntax for awk command is
awk '/search_pattern/ { action_to_take_if_pattern_matches; }' file_to_parse
Lets take following file /etc/passwd. Here’s the sample data that this file contains:
root:x:0:0:root:/root:/usr/bin/zsh
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
So now lets get only username from this file. Where -F specifies that on which base we are going to separate the fields. In our case it’s :. { print $1 } means print out the first matching field.
awk -F':' '{ print $1 }' /etc/passwd
After running the above command you will get following output.
root
daemon
bin
sys
sync
For more detail on how to use awk, check following link.
b. cut
Remove sections from each line of files
example.txt
red riding hood went to the park to play
show me columns 2 , 7 , and 9 with a space as a separator
cut -d " " -f2,7,9 example.txt
riding park play
c. echo
Display a line of text
display “Hello World”
echo Hello World
Hello World
display “Hello World” with newlines between words
echo -ne "Hello\nWorld\n"
Hello
World
d. egrep
Print lines matching a pattern - Extended Expression (alias for: ‘grep -E’)
example.txt
Lorem ipsum
dolor sit amet,
consetetur
sadipscing elitr,
sed diam nonumy
eirmod tempor
invidunt ut labore
et dolore magna
aliquyam erat, sed
diam voluptua. At
vero eos et
accusam et justo
duo dolores et ea
rebum. Stet clita
kasd gubergren,
no sea takimata
sanctus est Lorem
ipsum dolor sit
amet.
display lines that have either “Lorem” or “dolor” in them.
egrep '(Lorem|dolor)' example.txt
or
grep -E '(Lorem|dolor)' example.txt
Lorem ipsum
dolor sit amet,
et dolore magna
duo dolores et ea
sanctus est Lorem
ipsum dolor sit
e. fgrep
Print lines matching a pattern - FIXED pattern matching (alias for: ‘grep -F’)
example.txt
Lorem ipsum
dolor sit amet,
consetetur
sadipscing elitr,
sed diam nonumy
eirmod tempor
foo (Lorem|dolor)
invidunt ut labore
et dolore magna
aliquyam erat, sed
diam voluptua. At
vero eos et
accusam et justo
duo dolores et ea
rebum. Stet clita
kasd gubergren,
no sea takimata
sanctus est Lorem
ipsum dolor sit
amet.
Find the exact string ‘(Lorem|dolor)’ in example.txt
fgrep '(Lorem|dolor)' example.txt
or
grep -F '(Lorem|dolor)' example.txt
foo (Lorem|dolor)
f. fmt
Simple optimal text formatter
example: example.txt (1 line)
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
output the lines of example.txt to 20 character width
cat example.txt | fmt -w 20
Lorem ipsum
dolor sit amet,
consetetur
sadipscing elitr,
sed diam nonumy
eirmod tempor
invidunt ut labore
et dolore magna
aliquyam erat, sed
diam voluptua. At
vero eos et
accusam et justo
duo dolores et ea
rebum. Stet clita
kasd gubergren,
no sea takimata
sanctus est Lorem
ipsum dolor sit
amet.
g. grep
Looks for text inside files. You can use grep to search for lines of text that match one or many regular expressions, and outputs only the matching lines.
grep pattern filename
Example:
$ grep admin /etc/passwd
_kadmin_admin:*:218:-2:Kerberos Admin Service:/var/empty:/usr/bin/false
_kadmin_changepw:*:219:-2:Kerberos Change Password Service:/var/empty:/usr/bin/false
_krb_kadmin:*:231:-2:Open Directory Kerberos Admin Service:/var/empty:/usr/bin/false
You can also force grep to ignore word case by using -i option. -r can be used to search all files under the specified directory, for example:
$ grep -r admin /etc/
And -w to search for words only. For more detail on grep, check following link.
h. nl
Number lines of files
example.txt
Lorem ipsum
dolor sit amet,
consetetur
sadipscing elitr,
sed diam nonumy
eirmod tempor
invidunt ut labore
et dolore magna
aliquyam erat, sed
diam voluptua. At
vero eos et
accusam et justo
duo dolores et ea
rebum. Stet clita
kasd gubergren,
no sea takimata
sanctus est Lorem
ipsum dolor sit
amet.
show example.txt with line numbers
nl -s". " example.txt
1. Lorem ipsum
2. dolor sit amet,
3. consetetur
4. sadipscing elitr,
5. sed diam nonumy
6. eirmod tempor
7. invidunt ut labore
8. et dolore magna
9. aliquyam erat, sed
10. diam voluptua. At
11. vero eos et
12. accusam et justo
13. duo dolores et ea
14. rebum. Stet clita
15. kasd gubergren,
16. no sea takimata
17. sanctus est Lorem
18. ipsum dolor sit
19. amet.
i. sed
Stream editor for filtering and transforming text
example.txt
Hello This is a Test 1 2 3 4
replace all spaces with hyphens
sed 's/ /-/g' example.txt
Hello-This-is-a-Test-1-2-3-4
replace all digits with “d”
sed 's/[0-9]/d/g' example.txt
Hello This is a Test d d d d
j. sort
Sort lines of text files
example.txt
f
b
c
g
a
e
d
sort example.txt
sort example.txt
a
b
c
d
e
f
g
randomize a sorted example.txt
sort example.txt | sort -R
b
f
a
c
d
g
e
k. tr
Translate or delete characters
example.txt
Hello World Foo Bar Baz!
take all lower case letters and make them upper case
cat example.txt | tr 'a-z' 'A-Z'
HELLO WORLD FOO BAR BAZ!
take all spaces and make them into newlines
cat example.txt | tr ' ' '\n'
Hello
World
Foo
Bar
Baz!
l. uniq
Report or omit repeated lines
example.txt
a
a
b
a
b
c
d
c
show only unique lines of example.txt (first you need to sort it, otherwise it won’t see the overlap)
sort example.txt | uniq
a
b
c
d
show the unique items for each line, and tell me how many instances it found
sort example.txt | uniq -c
3 a
2 b
2 c
1 d
m. wc
Tells you how many lines, words and characters there are in a file.
wc filename
Example:
$ wc demo.txt
7459 15915 398400 demo.txt
Where 7459 is lines, 15915 is words and 398400 is characters.
1.3. Directory Operations
| cd | mkdir | pwd |
a. cd
Moves you from one directory to other. Running this
$ cd
moves you to home directory. This command accepts an optional dirname, which moves you to that directory.
cd dirname
b. mkdir
Makes a new directory.
mkdir dirname
c. pwd
Tells you which directory you currently are in.
pwd
1.4. SSH, System Info & Network Operations
| bg | cal | date | df | dig | du | fg | finger | jobs | last |
| man | passwd | ping | ps | quota | scp | ssh | top | uname | uptime |
| w | wget | whoami | whois |
a. bg
Lists stopped or background jobs; resume a stopped job in the background.
b. cal
Shows the month’s calendar.
c. date
Shows the current date and time.
d. df
Shows disk usage.
e. dig
Gets DNS information for domain.
dig domain
f. du
Shows the disk usage of files or directories. For more information on this command check this link
du [option] [filename|directory]
Options:
-h(human readable) Displays output it in kilobytes (K), megabytes (M) and gigabytes (G).-s(supress or summarize) Outputs total disk space of a directory and supresses reports for subdirectories.
Example:
du -sh pictures
1.4M pictures
g. fg
Brings the most recent job in the foreground.
h. finger
Displays information about user.
finger username
i. jobs
Lists the jobs running in the background, giving the job number.
j. last
Lists your last logins of specified user.
last yourUsername
k. man
Shows the manual for specified command.
man command
l. passwd
Allows the current logged user to change their password.
m. ping
Pings host and outputs results.
ping host
n. ps
Lists your processes.
ps -u yourusername
Use the flags ef. e for every process and f for full listing.
ps -ef
o. quota
Shows what your disk quota is.
quota -v
p. scp
Transfer files between a local host and a remote host or between two remote hosts.
copy from local host to remote host
scp source_file user@host:directory/target_file
copy from remote host to local host
scp user@host:directory/source_file target_file
scp -r user@host:directory/source_folder target_folder
This command also accepts an option -P that can be used to connect to specific port.
scp -P port user@host:directory/source_file target_file
q. ssh
ssh (SSH client) is a program for logging into and executing commands on a remote machine.
ssh user@host
This command also accepts an option -p that can be used to connect to specific port.
ssh -p port user@host
r. top
Displays your currently active processes.
s. uname
Shows kernel information.
uname -a
t. uptime
Shows current uptime.
u. w
Displays who is online.
v. wget
Downloads file.
wget file
w. whoami
Return current logged in username.
x. whois
Gets whois information for domain.
whois domain
1.5. Process Monitoring Operations
| kill | killall | & | nohup |
a. kill
Kills (ends) the processes with the ID you gave.
kill PID
b. killall
Kill all processes with the name.
killall processname
c. &
The & symbol instructs the command to run as a background process in a subshell.
command &
d. nohup
nohup stands for “No Hang Up”. This allows to run command/process or shell script that can continue running in the background after you log out from a shell.
nohup command
Combine it with & to create background processes
nohup command &
2. Basic Shell Programming
The first line that you will write in bash script files is called shebang. This line in any script determines the script’s ability to be executed like a standalone executable without typing sh, bash, python, php etc beforehand in the terminal.
#!/usr/bin/env bash
2.1. Variables
Creating variables in bash is similar to other languages. There are no data types. A variable in bash can contain a number, a character, a string of characters, etc. You have no need to declare a variable, just assigning a value to its reference will create it.
Example:
str="hello world"
The above line creates a variable str and assigns “hello world” to it. The value of variable is retrieved by putting the $ in the beginning of variable name.
Example:
echo $str # hello world
2.2. Array
Like other languages bash has also arrays. An array is a variable containing multiple values. There’s no maximum limit on the size of array. Arrays in bash are zero based. The first element is indexed with element 0. There are several ways for creating arrays in bash which are given below.
Examples:
array[0]=val
array[1]=val
array[2]=val
array=([2]=val [0]=val [1]=val)
array=(val val val)
To display a value at specific index use following syntax:
${array[i]} # where i is the index
If no index is supplied, array element 0 is assumed. To find out how many values there are in the array use the following syntax:
${#array[@]}
Bash has also support for the ternary conditions. Check some examples below.
${varname:-word} # if varname exists and isn't null, return its value; otherwise return word
${varname:=word} # if varname exists and isn't null, return its value; otherwise set it word and then return its value
${varname:+word} # if varname exists and isn't null, return word; otherwise return null
${varname:offset:length} # performs substring expansion. It returns the substring of $varname starting at offset and up to length characters
2.3 String Substitution
Check some of the syntax on how to manipulate strings
${variable#pattern} # if the pattern matches the beginning of the variable's value, delete the shortest part that matches and return the rest
${variable##pattern} # if the pattern matches the beginning of the variable's value, delete the longest part that matches and return the rest
${variable%pattern} # if the pattern matches the end of the variable's value, delete the shortest part that matches and return the rest
${variable%%pattern} # if the pattern matches the end of the variable's value, delete the longest part that matches and return the rest
${variable/pattern/string} # the longest match to pattern in variable is replaced by string. Only the first match is replaced
${variable//pattern/string} # the longest match to pattern in variable is replaced by string. All matches are replaced
${#varname} # returns the length of the value of the variable as a character string
2.4. Functions
As in almost any programming language, you can use functions to group pieces of code in a more logical way or practice the divine art of recursion. Declaring a function is just a matter of writing function my_func { my_code }. Calling a function is just like calling another program, you just write its name.
function name() {
shell commands
}
Example:
#!/bin/bash
function hello {
echo world!
}
hello
function say {
echo $1
}
say "hello world!"
When you run the above example the hello function will output “world!”. The above two functions hello and say are identical. The main difference is function say. This function, prints the first argument it receives. Arguments, within functions, are treated in the same manner as arguments given to the script.
2.5. Conditionals
The conditional statement in bash is similar to other programming languages. Conditions have many form like the most basic form is if expression then statement where statement is only executed if expression is true.
if [ expression ]; then
will execute only if expression is true
else
will execute if expression is false
fi
Sometime if conditions becoming confusing so you can write the same condition using the case statements.
case expression in
pattern1 )
statements ;;
pattern2 )
statements ;;
...
esac
Expression Examples:
statement1 && statement2 # both statements are true
statement1 || statement2 # at least one of the statements is true
str1=str2 # str1 matches str2
str1!=str2 # str1 does not match str2
str1<str2 # str1 is less than str2
str1>str2 # str1 is greater than str2
-n str1 # str1 is not null (has length greater than 0)
-z str1 # str1 is null (has length 0)
-a file # file exists
-d file # file exists and is a directory
-e file # file exists; same -a
-f file # file exists and is a regular file (i.e., not a directory or other special type of file)
-r file # you have read permission
-s file # file exists and is not empty
-w file # you have write permission
-x file # you have execute permission on file, or directory search permission if it is a directory
-N file # file was modified since it was last read
-O file # you own file
-G file # file's group ID matches yours (or one of yours, if you are in multiple groups)
file1 -nt file2 # file1 is newer than file2
file1 -ot file2 # file1 is older than file2
-lt # less than
-le # less than or equal
-eq # equal
-ge # greater than or equal
-gt # greater than
-ne # not equal
2.6. Loops
There are three types of loops in bash. for, while and until.
Different for Syntax:
for x := 1 to 10 do
begin
statements
end
for name [in list]
do
statements that can use $name
done
for (( initialisation ; ending condition ; update ))
do
statements...
done
while Syntax:
while condition; do
statements
done
until Syntax:
until condition; do
statements
done
3. Tricks
Set an alias
Open bash_profile by running following command nano ~/.bash_profile
alias dockerlogin=’ssh www-data@adnan.local -p2222’ # add your alias in .bash_profile
To quickly go to a specific directory
nano ~/.bashrc
export hotellogs=”/workspace/hotel-api/storage/logs”
source ~/.bashrc
cd $hotellogs
Exit traps
Make your bash scripts more robust by reliably performing cleanup.
function finish {
# your cleanup here. e.g. kill any forked processes
jobs -p | xargs kill
}
trap finish EXIT
Saving your environment variables
When you do export FOO = BAR, your variable is only exported in this current shell and all its children, to persist in the future you can simply append in your ~/.bash_profile file the command to export your variable
echo export FOO=BAR >> ~/.bash_profile
Accessing your scripts
You can easily access your scripts by creating a bin folder in your home with mkdir ~/bin, now all the scripts you put in this folder you can access in any directory.
If you can not access, try append the code below in your ~/.bash_profile file and after do source ~/.bash_profile.
# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
PATH="$HOME/bin:$PATH"
fi
4. Debugging
You can easily debug the bash script by passing different options to bash command. For example -n will not run commands and check for syntax errors only. -v echo commands before running them. -x echo commands after command-line processing.
bash -n scriptname
bash -v scriptname
bash -x scriptname
1 – SYSTEM INFORMATION
Display Linux system information
uname -a
Display kernel release information
uname -r
Show which version of redhat installed
cat /etc/redhat-release
Show how long the system has been running + load
uptime
Show system host name
hostname
Display the IP addresses of the host
hostname -I
Show system reboot history
last reboot
Show the current date and time
date
Show this month’s calendar
cal
Display who is online
w
Who you are logged in as
whoami
2 – HARDWARE INFORMATION
Display messages in kernel ring buffer
dmesg
Display CPU information
cat /proc/cpuinfo
Display memory information
cat /proc/meminfo
Display free and used memory ( -h for human readable, -m for MB, -g for GB.)
free -h
Display PCI devices
lspci -tv
Display USB devices
lsusb -tv
Display DMI/SMBIOS (hardware info) from the BIOS
dmidecode
Show info about disk sda
hdparm -i /dev/sda
Perform a read speed test on disk sda
hdparm -tT /dev/sda
Test for unreadable blocks on disk sda
badblocks -s /dev/sda
3 – PERFORMANCE MONITORING AND STATISTICS
Display and manage the top processes
top
Interactive process viewer (top alternative)
htop
Display processor related statistics
mpstat 1
Display virtual memory statistics
vmstat 1
Display I/O statistics
iostat 1
Display the last 100 syslog messages (Use /var/log/syslog for Debian based systems.)
tail 100 /var/log/messages
Capture and display all packets on interface eth0
tcpdump -i eth0
Monitor all traffic on port 80 ( HTTP )
tcpdump -i eth0 ‘port 80’
List all open files on the system
lsof
List files opened by user
lsof -u user
Display free and used memory ( -h for human readable, -m for MB, -g for GB.)
free -h
Execute “df -h”, showing periodic updates
watch df -h
4 – USER INFORMATION AND MANAGEMENT
Display the user and group ids of your current user.
id
Display the last users who have logged onto the system.
last
Show who is logged into the system.
who
Show who is logged in and what they are doing.
w
Create a group named “test”.
groupadd test
Create an account named john, with a comment of “John Smith” and create the user’s home directory.
useradd -c “John Smith” -m john
Delete the john account.
userdel john
Add the john account to the sales group
usermod -aG sales john
5 – FILE AND DIRECTORY COMMANDS
List all files in a long listing (detailed) format
ls -al
Display the present working directory
pwd
Create a directory
mkdir directory
Remove (delete) file
rm file
Remove the directory and its contents recursively
rm -r directory
Force removal of file without prompting for confirmation
rm -f file
Forcefully remove directory recursively
rm -rf directory
Copy file1 to file2
cp file1 file2
Copy source_directory recursively to destination. If destination exists, copy source_directory into destination, otherwise create destination with the contents of source_directory.
cp -r source_directory destination
Rename or move file1 to file2. If file2 is an existing directory, move file1 into directory file2
mv file1 file2
Create symbolic link to linkname
ln -s /path/to/file linkname
Create an empty file or update the access and modification times of file.
touch file
View the contents of file
cat file
Browse through a text file
less file
Display the first 10 lines of file
head file
Display the last 10 lines of file
tail file
Display the last 10 lines of file and “follow” the file as it grows.
tail -f file
6 – PROCESS MANAGEMENT
Display your currently running processes
ps
Display all the currently running processes on the system.
ps -ef
Display process information for processname
ps -ef | grep processname
Display and manage the top processes
top
Interactive process viewer (top alternative)
htop
Kill process with process ID of pid
kill pid
Kill all processes named processname
killall processname
Start program in the background
program &
Display stopped or background jobs
bg
Brings the most recent background job to foreground
fg
Brings job n to the foreground
fg n
7 – FILE PERMISSIONS
Linux chmod example PERMISSION EXAMPLE
U G W
rwx rwx rwx chmod 777 filename
rwx rwx r-x chmod 775 filename
rwx r-x r-x chmod 755 filename
rw- rw- r-- chmod 664 filename
rw- r-- r-- chmod 644 filename
NOTE: Use 777 sparingly!
LEGEND
U = User
G = Group
W = World
r = Read
w = write
x = execute
- = no access
8 – NETWORKING
Display all network interfaces and ip address
ifconfig -a
Display eth0 address and details
ifconfig eth0
Query or control network driver and hardware settings
ethtool eth0
Send ICMP echo request to host
ping host
Display whois information for domain
whois domain
Display DNS information for domain
dig domain
Reverse lookup of IP_ADDRESS
dig -x IP_ADDRESS
Display DNS ip address for domain
host domain
Display the network address of the host name.
hostname -i
Display all local ip addresses
hostname -I
Download http://domain.com/file
wget http://domain.com/file
Display listening tcp and udp ports and corresponding programs
netstat -nutlp
9 – ARCHIVES (TAR FILES)
Create tar named archive.tar containing directory.
tar cf archive.tar directory
Extract the contents from archive.tar.
tar xf archive.tar
Create a gzip compressed tar file name archive.tar.gz.
tar czf archive.tar.gz directory
Extract a gzip compressed tar file.
tar xzf archive.tar.gz
Create a tar file with bzip2 compression
tar cjf archive.tar.bz2 directory
Extract a bzip2 compressed tar file.
tar xjf archive.tar.bz2
10 – INSTALLING PACKAGES
Search for a package by keyword.
yum search keyword
Install package.
yum install package
Display description and summary information about package.
yum info package
Install package from local file named package.rpm
rpm -i package.rpm
Remove/uninstall package.
yum remove package
Install software from source code.
tar zxvf sourcecode.tar.gz cd sourcecode ./configure make make install
11 – SEARCH
Search for pattern in file
grep pattern file
Search recursively for pattern in directory
grep -r pattern directory
Find files and directories by name
locate name
Find files in /home/john that start with “prefix”.
find /home/john -name ‘prefix*’
Find files larger than 100MB in /home
find /home -size +100M
12 – SSH LOGINS
Connect to host as your local username.
ssh host
Connect to host as user
ssh user@host
Connect to host using port
ssh -p port user@host
13 – FILE TRANSFERS
Secure copy file.txt to the /tmp folder on server
scp file.txt server:/tmp
Copy *.html files from server to the local /tmp folder.
scp server:/var/www/*.html /tmp
Copy all files and directories recursively from server to the current system’s /tmp folder.
scp -r server:/var/www /tmp
Synchronize /home to /backups/home
rsync -a /home /backups/
Synchronize files/directories between the local and remote system with compression enabled
rsync -avz /home server:/backups/
14 – DISK USAGE
Show free and used space on mounted filesystems
df -h
Show free and used inodes on mounted filesystems
df -i
Display disks partitions sizes and types
fdisk -l
Display disk usage for all files and directories in human readable format
du -ah
Display total disk usage off the current directory
du -sh
15 – DIRECTORY NAVIGATION
To go up one level of the directory tree. (Change into the parent directory.)
cd ..
Go to the $HOME directory
cd
Change to the /etc directory
cd /etc
Conda/Anaconda
This link provides some simple commands for working with the conda CLI.