sudo tcpdump -ni lo0 -s 0 -A tcp port 3000
Author: admin
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Sniffing tcp with tcpdump
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Set automatic httpd daemon start
This comand set executions permissions to the script and with chkconfig we create a Start link to the rc.d system.
chmod 755 /etc/init.d/httpd ; chkconfig --add httpd /etc/init.d/httpd start
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Dirty script to find out free storage space in mount points
Dirty script to find out free storage space.
for path in `mount | awk '/^\/dev/ {print $3}'`; do df -h "$path"; done; -
Find symbolic links to directory
find . -lname '*directory_name*' 2>/dev/null -
Nat with iptables
Example of nat in iptables.
YourIP=1.2.3.4
YourPort=80
TargetIP=2.3.4.5
TargetPort=22iptables -t nat -A PREROUTING --dst $YourIP -p tcp --dport $YourPort -j DNAT \
--to-destination $TargetIP:$TargetPort
iptables -t nat -A POSTROUTING -p tcp --dst $TargetIP --dport $TargetPort -j SNAT \
--to-source $YourIP
iptables -t nat -A OUTPUT --dst $YourIP -p tcp --dport $YourPort -j DNAT \
--to-destination $TargetIP:$TargetPort -
Check if an input is numeric or char
With this script you can check if an argument to a script is numeric, char or alphanumeric.
[[ -z "$1" ]] && echo "I cant work without an input" && exit 1INPUT="$@"
[[ "$INPUT" == ?(+|-)+([0-9]) ]] && echo "$INPUT is numeric" && exit 0
[[ "$INPUT" == +([a-zA-Z]) ]] && echo "$INPUT is character" && exit 0
[[ "$INPUT" == *([0-9]|[a-zA-Z])* ]] && echo "$INPUT is alpha-numeric" && exit 0
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List large files in Linux
Command to find and list all files above a defined size. Works for debian based distros and Centos. If the output its wrong in other systems, you can play with awk params.
find . -type f -size +50000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }' -
How to generate a tar gz file from a file list
Easy example of tar use. We provide a list of files to archive them in one tar file.
tar zcvf myFile.tar.gz file1.txt file2.txt file3.txt file4.txt -
Mirror two local directories with rsync
To copy 2 directories in a little more advanded way you can use rsync.
# mirror Dir to Dir2cd ~/Dir
rsync -vaz ~/Dir2 .