Sources:
- Advanced linux commands – http://www.linuxquestions.org/linux/answers/Security/Advance_linux_command
- http://www.linuxquestions.org/questions/linux-general-1/tricks-and-hints-27957/
- Unix Guide’s (http://www.unixguide.net/) rosetta stone for unix commands – http://www.unixguide.net/cgi-bin/unixguide.cgi – covers: AIX, FreeBSD, HP-UX, LINUX(RedHat), SOLARIS and Tru64.
- “A Sysadmin’s Universal Translator (Rosetta Stone)” – http://bhami.com/rosetta.html
- “Rosetta Stone for Scripting Languages” – http://www.lurklurk.org/rosetta.html
- “Basic networking commands in linux/unix” by Javin Paul (at TIBCO RV FIX PROTOCOL JAVA TUTORIAL; 2010.10.03) – http://javarevisited.blogspot.com/2010/10/basic-networking-commands-in-linuxunix.html
- Unix tips at SuperUser – http://superuser.com/questions/tagged/unix | Bash – http://superuser.com/questions/tagged/bash | Linux – http://superuser.com/questions/tagged/linux
- “BASH Frequently Asked Questions” and Greg’s Wiki – http://mywiki.wooledge.org/BashFAQ/
System information
Check cpu info:
cat /proc/cpuinfo |
Usernames
To get the list of usernames with its user ID in formatted way:
awk -F":" '{ print "username: " $1 "\t\tuid:" $3 }' /etc/passwd
|
Filenames
Find the particular string from the list of files in current directory:
cd /etc for i in $(find -type f); do grep -iH nfsnobody $i; done |
Or
grep -iH nfsnobody * |
Counting words
Get the no of occurrences of particular word in file:
awk '/ServerName/ {i=i+1} END {print i}' /etc/httpd/conf/httpd.conf
grep ServerName /etc/httpd/conf/httpd.conf
|
Semaphores
To delete resources of semaphore arrays from memory:
ipcs -s |
grep apache |
perl -e 'while () { @a=split(/\s+/); print`ipcrm sem $a[1]`}'
|
Convering Unix timestamp to human readable format
All one needs here is neatly summarized by Anton Olson in his blog posting “BASH: Convert Unix Timestamp to a Date” – http://www.antonolsen.com/2006/04/06/bash-convert-unix-timestamp-to-a-date/:
- 1) perl -e “require ‘ctime.pl’; print &ctime($EPOCH);” – where ctime is a Perl module (available where?)
- 2) perl -e “print scalar(localtime($EPOCH))”
- 3) echo $EPOCH|awk ‘{print strftime(“%c”,$1)}’
- 4) # date -d @1000000042 on Linux (and Cygwin)
- 5) $ date -d ’1970-01-01 sec’. It is important to use the GMT tag:
- #date -d ’1970-01-01 1000000000 sec GMT’ with output: Sat Sep 8 20:46:40 CDT 2001
- #date -d ’1970-01-01 1000000000 sec’ gives output: Sun Sep 9 02:46:40 CDT 2001
- 6) $ date -r 1229519950 – on FreeBSD
The third method works fine if you have available only shell (e.g. working in Cygwin) and does not require Perl interpreter. For example:
In: echo 101000070 | awk '{print strftime("%c",$1)}'
Out: Wed Mar 14 19:34:30 1973
|
Perl
To check whether perl module is installed correctly or not: if all is correct then output of this command nothing
perl -e 'require Mail::SPF::Query' |
To install CPAN module:
cpan cpan> install Mail::SPF::Query CPAN: Storable loaded ok Going to read /root/.cpan/Metadata Database was generated on Thu, 24 Nov 2005 14:54:20 GMT Mail::SPF::Query is up to date. |
IP Addresses
To get the list of IP addresses in the server:
ifconfig | grep -vw inet6 | grep -w inet | cut -d : -f 2 | cut -d \ -f 1 |
Find list of IP address along with eth device and network mask:
ifconfig | cut -d " " -f1,12,16 | grep -A 1 eth | tr -d - | tr -s "\n" |sed -e :a -e N -e 's/\n/ /' |
hard disk
Know the performance of your HardDisk: change the device address as per your servers configuration
hdparm -Tt /dev/sda |
Logging
Get the customized output of raw accesslog of httpd: Navigate the folder where your http access log reside, then execute following:
tail -f access_log |
awk '{if ($11 ~"\"-\"") print $1, $7, $12; else print $1, $10, $11, $12}'
|
Checking SSH failure log (in GNU/Linux Debian)
/bin/cat /var/log/auth.log |
grep sshd:auth |
grep failure |
awk '{print $1"-" $2 "-" $3 "-->" $12 "->" $14 "->" $15}'
|
Open connections
The details of the present http connections can be found by using:
netstat -plan |
grep ":80 " |
awk {'print $5'} |
awk -F: {'print $1'}|
sort
cat /proc/net/ip_conntrack |
grep "port=80" |
wc -l
|
Number of connection from the particular IP addfess:
netstat -ntu | awk '{print $5}'| cut -d: -f1 | sort | uniq -c | sort -nr | more
|
No of conections:
netstat -alntp /sbin/ldconfig /usr/local/lib - Update the system linker cache |
Real Time Network Activity Examples:
root# watch -d "netstat -nalp |grep -v DGRAM |grep -v STREAM |grep -v LISTEN" root# watch "netstat -nalp"|grep ":TCP PORT Number" root# watch "netstat -nalp"|grep ":22" |
Port scanning
Port scanning using nmap:
You can customized it to get more informative output
nmap -sS localhost - |
instead host localhost, it could be IP address of another server which is in question
Bash loops
You can execute bash command a certain number of times by using something similar to the following:
n=0;while test -$n -gt -10; do echo n=$n; n=$[$n+1]; done |
that code will print “n=0”, “n=1”, and so on 10 times.
Directory content
Only get the listing of directories:
ls -F $1 | grep \/ | sed -e 's/\/$/4/g' |
Killing processes
Kill program one time click base keyword:
for a in $( ps aux |
grep "some-thing-text" |
awk '{ print $2 }'); do kill $a; done;
|
Kill crontab processes:
for a in $( ps aux | grep "/USR/SBIN/CRON" | awk '{ print $2 }'); do kill $a; done;
|
Environment variables
CDPATH env variable, if it is set for instance
[bash ~]$ export CDPATH=/usr/local/apache |
when you enter from any directory you’re in
[bash /var/log]$ cd htdocs |
it will take you to /usr/local/apache/htdocs.
Bash completion, command repetition and command history
- !! at the command shell executes the last executed command
- !m – executes the last command in history that starts with m for instance mail
- !m:p – will print what was the last command that starts with m
vi
- hitting twice z while holding a shift key in vi in command mode saves the edited file and quits vi
File dates
Updating atime on file foo (e.g. to 21:00 of Jan 1 1970):
touch -t 197001012100 foo |
help, man, apropos
Redirect a rather big man page to a text file in easy readable format:
man manpage | col -b > manpage.txt |
Conversion DOS to UNIX and vice versa
Getting rid off annoying ^M (CTRL-M) in DOS-like files:
tr -d "15" /unixfile |
In vi editor use search-and-replace command:
:%s/^M//g |
To get ^M (in vi)you press CTRL+V+M
Related here: Unix system administration – https://eikonal.wordpress.com/2011/03/02/unix-system-administration/ | Cygwin stuff – https://eikonal.wordpress.com/2010/07/12/cygwin-stuff | MS Windows Registry transversal by Cygwin – https://eikonal.wordpress.com/2011/03/01/registry-transversal-by-cygwin
Related here: Scripting languages – https://eikonal.wordpress.com/2010/06/15/awk-sed/ | Unix tricks – https://eikonal.wordpress.com/2011/02/15/unix-tricks/ | SED tricks – https://eikonal.wordpress.com/2010/10/05/sed-tricks/ | Memory of things disappearing > nmap stuff > getports.awk – https://eikonal.wordpress.com/2010/06/23/memory-of-things-disappearing-nmap-stuff-getports-awk/ | AWK – https://eikonal.wordpress.com/2011/09/30/awk/
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