VirtualBox Copy/Paste not working?

Open the settings (Host Key (usually right ctrl) + s) > Advanced > Shared Clipboard > Enable

Fire the below command and restart the VM

sudo apt-get install virtualbox-guest-dkms

Hope this helps!

Installing Nagios Core without "root" permission

Complete guide to install Nagios in Linux without "root" permission

1) Installing HTTPD

# All the installation will be done under /home/maximus/tools

wget http://www-eu.apache.org/dist//httpd/httpd-2.4.23.tar.gz
wget http://www-eu.apache.org/dist//apr/apr-util-1.5.4.tar.gz
wget http://www-eu.apache.org/dist//apr/apr-1.5.2.tar.gz

tar -xzvf httpd-2.4.23.tar.gz
tar -xzvf apr-1.5.2.tar.gz
tar -xzvf apr-util-1.5.4.tar.gz

cp -r apr-1.5.2 httpd-2.4.23/srclib/apr
cp -r apr-util-1.5.4 httpd-2.4.23/srclib/apr-util
cd httpd-2.4.23
./configure --prefix=/home/maximus/tools -with-included-apr
make
make install

2) Install PHP

wget http://php.net/get/php-7.0.9.tar.gz
tar -xzvf php-7.0.9.tar.gz
cd php-7.0.9
./configure --prefix=/home/maximus/tools --with-apxs2=/home/maximus/tools/bin/apxs --with-config-file-path=/home/maximus/tools/conf/
make
make install
cp php.ini-development /home/maximus/tools/conf/php.ini

# Add the following lines in /home/maximus/tools/conf/httpd.conf to enable PHP and CGI, 
# and to change the default HTTP port no

Listen 5555
LoadModule cgid_module modules/mod_cgid.so
LoadModule php7_module        modules/libphp7.so
<FilesMatch \.php$>
    SetHandler application/x-httpd-php
</FilesMatch>

3) Install GD

wget http://www.boutell.com/gd/http/gd-2.0.33.tar.gz
tar -xzvf gd-2.0.33.tar.gz
cd gd-2.0.33
./configure --prefix=/home/maximus/tools/
make
make install


4) Install Nagios

wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.1.1.tar.gz
tar -xzvf nagios-4.1.1.tar.gz
cd nagios-4.1.1

# maximus is a non-previliged user. eng is the group which maximus belongs to. 
# Feel free to change it as per your needs
./configure --prefix=/home/maximus/tools/nagios --with-cgiurl=/nagios/cgi-bin --with-htmurl=/nagios/ --with-nagios-user=maximus --with-nagios-group=eng --with-command-group=eng --with-gd-lib=/home/maximus/tools/lib --with-gd-inc=/home/maximus/tools/include --with-httpd-conf=/home/maximus/tools/conf
make all
make install

# In the Makefile (in current directory) add the entry DESTDIR=/home/maximus/tools/ 
# and the execute the next command
make install-init
# Now remove the entry which we just added
make install-commandmode
make install-config
make install-webconf
cp -R contrib/eventhandlers/ /home/maximus/tools/nagios/libexec/

# Provide a password for the user nagiosadmin (you can chose your own username). 
# You will be using this login to the Nagios Core Web 
cd /home/maximus/tools/nagios/etc/
htpasswd -c htpasswd.users nagiosadmin

# Add the following line to /home/maximus/tools/conf/httpd.conf

Include conf/nagios.conf

5) Install the Nagios Core Plugins

wget http://www.nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz
tar -xzvf nagios-plugins-2.1.1.tar.gz
cd nagios-plugins-2.1.1
./configure --with-nagios-user=maximus --with-nagios-group=eng --prefix=/home/maximus/tools/nagios/
make
make install

To start the all the services
/home/maximus/tools/bin/apachectl start
/home/maximus/tools/etc/rc.d/init.d/nagios start

To stop the all the services
/home/maximus/tools/bin/apachectl stop
/home/maximus/tools/etc/rc.d/init.d/nagios stop

Web Address
http://localhost:5555/nagios/index.php

Hope this helps!!

HC-SR04 with Raspberry Pi - Distance

HC-SR04 (Ultrasonic Module) interfacing with Raspberry Pi for distance calculation.

Will provide the schematics soon.

/*
 * HC-SR04 <> RPi
 * To calculate the distance
 * Using the libbcm2835 library
 * Author : Ahamed EN (ahamed.en@gmail.com)
 * 20-March-2016
 */
#include <bcm2835.h>
#include <stdio.h>
#include <sys/time.h>

/* We will be using
 * Pin#16 (GPIO23) as Trigger
 * Pin#18 (GPIO24) for Echo
 */
#define TRIGGER RPI_GPIO_P1_16
#define ECHO    RPI_GPIO_P1_18

int main(int argc, char **argv)
{

    if (!bcm2835_init())
        return 1;

    struct timeval start, end;
    float duration;

    bcm2835_gpio_fsel(TRIGGER, BCM2835_GPIO_FSEL_OUTP);
    bcm2835_gpio_fsel(ECHO, BCM2835_GPIO_FSEL_INPT);

    bcm2835_gpio_write(TRIGGER, LOW);
    bcm2835_gpio_write(ECHO, LOW);
    bcm2835_delay(2);

    bcm2835_gpio_write(TRIGGER, HIGH);
    usleep(10); /* As per the HC-SR04 manual */
    bcm2835_gpio_write(TRIGGER, LOW);

    /* Wait until we get a HIGH */
    while(!bcm2835_gpio_lev(ECHO));
    gettimeofday(&start, NULL);

    /* Wait until we get a LOW */
    while(bcm2835_gpio_lev(ECHO));
    gettimeofday(&end, NULL);

    /*
     * speed = distance/time
     * speed = 340m/s = 34300cm/s (speed of sound)
     *
     * 34300 = distance/time
     *
     * distance = time/2 * 34300 (time/2 because what we got is the time
     *                              for to and fro)
     */

    duration = (end.tv_sec - start.tv_sec) * 1000.0;
    duration += (end.tv_usec - start.tv_usec) / 1000.0;
    duration = duration/1000; /* to seconds */

    float distance = duration/2 * 34300;

    printf("Disatnce : %f cm\n", distance);

    bcm2835_delay(500);
    bcm2835_close();
    return 0;
}

Interfacing SIM800 module with Raspberry Pi via Serial Interface C program

Interfacing SIM800 module with R-Pi via Serial Interface using C program. Following program sends an SMS to the specified mobile number.

This program uses the normal C routines

R-Pi                 SIM800
                  
Pin#06(GND)  --------  GND
Pin#08(TXD0) --------  Rx
Pin#10(RXD0) --------  Tx

root@raspberrypi:~/sim# gcc send.c -o send_sms

root@raspberrypi:~/sim# ./send_sms
Writing to Port : AT
Read from port  : ATOK
Writing to Port : AT+CMGF=1
Read from port  : AT+CMGF=1OK
Writing to Port : AT+CNMI=2,1,0,0,0
Read from port  : AT+CNMI=2,1,0,0,0OK
Writing to Port : AT+CMGS="9535213788"
Read from port  : AT+CMGS="9535213788">
Writing to Port : PI_SIM800_TESTING

The received SMS

/*
 * SIM800 <> Raspberry Pi - Serial Interface
 * To send a SMS using SIM800 module via RPi
 * Author : Ahamed EN (ahamed.en@gmail.com)
 * Date : 20 March 2016
 */

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <termios.h>

/* This is R-Pi default serial port */
#define DEFAULT_PI_SERIAL_PORT "/dev/ttyAMA0"

typedef enum _mode_t{
    RW,
    WO,
    RO
}sim_mode_t;

static inline void error(char *err)
{
    printf("Error : %s\n", err);
}

#define ERROR(err) { printf("[%s %d] ", __func__, __LINE__); error(err); }

int open_serial_dev(char *serial_dev)
{

    if(!serial_dev){
        ERROR("serial_dev in NULL");
        return -1;
    }

    int fd;

    fd = open(serial_dev, O_RDWR | O_NOCTTY | O_NDELAY);
    if(fd < 0){
        ERROR("Could not open the serial device");
        return -1;
    }
    return fd;

}

/* To initialize the serial port via termios */
int serial_init(int fd)
{

    struct termios termios;
    int ret = 0;

    ret = tcgetattr (fd, &termios);
    if(ret < 0){
        ERROR("tcgetattr failed");
        return -1;
    }

    cfsetispeed(&termios, B9600);
    cfsetospeed(&termios, B9600);

    termios.c_iflag &= ~(IXANY | IXON | IXOFF);
    termios.c_lflag &= ~(ICANON | ECHO);
    termios.c_cflag |= (CLOCAL | CREAD);

    termios.c_cc[VMIN]  = 1;
    termios.c_cc[VTIME] = 10;

    ret = tcsetattr (fd, TCSANOW, &termios);
    if(ret < 0){
        ERROR("tcsetattr failed");
        return -1;
    }


    return 0;
}

void set_cmd(char *cmd, char *cmd_str)
{
    memset(cmd, 0, sizeof(cmd));
    strcpy(cmd, cmd_str);
}

int read_port(int fd, int ret)
{
    int rv = 0;
    int i = 0;
    char buf[64];
    if(ret){
        rv = read(fd, &buf, sizeof(buf));
        printf("Read from port\t: ");
        for(i=0; i<rv; i++){
            if(buf[i] == '\n' || buf[i] == '\r') continue;
            printf("%c", buf[i]);
        }
        printf("\n");
    }
    return rv;
}

int write_port(int fd, char *cmd, int len)
{
    if(fd < 0){
        ERROR("Invalid fd");
        return -1;
    }

    printf("Writing to Port\t: %s", cmd);

    int ret = 0;
    ret = write(fd, cmd, len);
    if(ret <= 0){
        ERROR("write failed");
    }
    return ret;

}

/* Function to write and read from the port */
void set_get_cmd(int fd, sim_mode_t mode, char *cmd_str)
{
    int ret;
    char cmd[64];
    set_cmd(cmd, cmd_str);
    ret = write_port(fd, cmd, strlen(cmd));
    usleep (100000);
    if(mode == WO){
        return;
    }
    read_port(fd, ret);
    return;

}

int main(int argc, char **argv)
{

    char *serial_dev = DEFAULT_PI_SERIAL_PORT;
    int ret = 0;
    int fd;


    if(argv[1]){
        serial_dev = argv[1];
    }

    fd = open_serial_dev(serial_dev);
    if(fd < 0){
        ERROR("Exiting");
        return -1;
    }

    ret = serial_init(fd);
    if(ret < 0){
        ERROR("Exiting");
        return -1;
    }

    /* Check the SIM800 Data sheet for the commands */

    set_get_cmd(fd, RW, "AT\r\n");
    set_get_cmd(fd, RW, "AT+CMGF=1\r\n");
    set_get_cmd(fd, RW, "AT+CNMI=2,1,0,0,0\r\n");

    /* Specify the 10 digit mobile # here */
    set_get_cmd(fd, RW, "AT+CMGS=\"9535213788\"\r\n");

    /* Following is your text message */
    set_get_cmd(fd, WO, "PI_SIM800_TESTING\r\n");

    set_get_cmd(fd, WO, "\x1A");

    printf("\n");

    return 0;

}

Guide to Linux Driver

/dev/hello_world: A Simple Introduction to Device Drivers under Linux - O'Reilly Media

CCIE Data Center :: Nexus :: FabricPath Overview

Multicast Part 1 - Intro