Finding list of installed files from a package in Linux

Recently we installed one package, but couldn’t understood which all files it installed on Ubuntu. You can use the command as, dpkg-query -L PACKAGE_NAME So, lets say, you want to identify which are files “openssh-server” package installed, then run the command as below, dpkg-query -L openssh-server /. /etc /etc/ufw /etc/ufw/applications.d /etc/ufw/applications.d/openssh-server /etc/pam.d /etc/pam.d/sshd /etc/init /etc/init/ssh.conf … Read more

How to disable and / or enable ICMP ping from Linux host ?

To disable the ICMP ping from certain linux host, lets say which has IP of use below command, Type below command on the console of linux PC on which you are trying to enable / disable the ping. $ sudo iptables -A INPUT -p icmp –icmp-type any -j REJECT $ sudo iptables -A OUTPUT … Read more

Understanding wireless beacon packet ( captured using pcap API’s )

As per Wikipedia, Beacon frame is one of the management frames in IEEE 802.11 based WLANs. It contains all the information about the network. Beacon frames are transmitted periodically, they serve to announce the presence of a wireless LAN and to synchronise the members of the service set. Beacon frames are transmitted by the access point (AP) in an infrastructure basic … Read more

Understanding pcap file format – part I – Global Header

The file must begin with a Section Header Block.  Below is typical configuration, with a single Section Header that covers the whole file. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SHB v1.0 | Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Typical configuration with a single Section Header Block The Section Header Block is mandatory. It identifies the beginning of a section of the capture dump … Read more

How to get mac-id using ipaddress in linux

Make sure you ping that IP atleast once so this can get address into ARP table. $ ping -c 1 PING ( 56(84) bytes of data.64 bytes from icmp_seq=1 ttl=128 time=4.68 ms— ping statistics —1 packets transmitted, 1 received, 0% packet loss, time 0msrtt min/avg/max/mdev = 4.681/4.681/4.681/0.000 ms Now user arp … Read more

Wi-Fi Initial Communication between device and access point

Following diagram shows the initial handshaking between the device ( like mobile ) and wireless access-point ( AP ) in open access mode and secured ( e.g. WPA ) mode, Authentication frame ( in open access ): 802.11 authentication is a process whereby the access point either accepts or rejects the identity of a radio … Read more

What is the Difference between Process and Thread ?

Creating a new thread is very similar to forking a new process, but there are differences. When a new process is forked, it shares relatively little data with the parent process which created it, when a new thread is created, it shares much more information (such as all the global variables and static local variables, … Read more

C program to check total and free RAM memory in Linux

Following C program helps you to identify what is the total and free memory / RAM available in your Linux machine. $ vim checkfreemem.c [bash] #include <stdio.h> #include <sys/sysinfo.h> void printmemsize(char *str, unsigned long ramsize) { printf("%s: %ld in bytes / %ld in KB / %ld in MB / %ld in GB\n",str, ramsize, ramsize/1024, (ramsize/1024)/1024, … Read more