SSH clients will automatically be disconnected from the server and prompt the below message after being idle or inactive for a while.

Read from remote host oseems.com: Connection reset by peer
Connection to oseems.com closed.

This is due to the SSH servers’ configuration (often by default) to avoid hanging sessions and free up resources.

If you have administrative access to the SSH servers, you can configure it so that it will not easily disconnect idle sessions. This could be achieved by setting the parameters for TCPKeepAlive, ClientAliveInterval, and ClientAliveCountMax as per the following;

TCPKeepAlive no 
ClientAliveInterval 30
ClientAliveCountMax 240

What it basically means is that the server will not send the TCP alive packet to check if the client’s connection is working, yet will still send the encrypted alive message every 30 seconds. It will only disconnect after at least 2 hours of inactivity.

The following is the full explanation for the options;

 TCPKeepAlive
         Specifies whether the system should send TCP keepalive messages to the other side.  If they are sent, death of the
         connection or crash of one of the machines will be properly noticed.  However, this means that connections will die
         if the route is down temporarily, and some people find it annoying.  On the other hand, if TCP keepalives are not
         sent, sessions may hang indefinitely on the server, leaving “ghost” users and consuming server resources.

         The default is “yes” (to send TCP keepalive messages), and the server will notice if the network goes down or the
         client host crashes.  This avoids infinitely hanging sessions.

         To disable TCP keepalive messages, the value should be set to “no”.

         This option was formerly called KeepAlive.

 ClientAliveCountMax
         Sets the number of client alive messages (see below) which may be sent without sshd(8) receiving any messages back
         from the client.  If this threshold is reached while client alive messages are being sent, sshd will disconnect the
         client, terminating the session.  It is important to note that the use of client alive messages is very different
         from TCPKeepAlive (below).  The client alive messages are sent through the encrypted channel and therefore will not
         be spoofable.  The TCP keepalive option enabled by TCPKeepAlive is spoofable.  The client alive mechanism is valu‐
         able when the client or server depend on knowing when a connection has become inactive.

         The default value is 3.  If ClientAliveInterval (see below) is set to 15, and ClientAliveCountMax is left at the
         default, unresponsive SSH clients will be disconnected after approximately 45 seconds.  This option applies to pro‐
         tocol version 2 only.

 ClientAliveInterval
         Sets a timeout interval in seconds after which if no data has been received from the client, sshd(8) will send a
         message through the encrypted channel to request a response from the client.  The default is 0, indicating that
         these messages will not be sent to the client.  This option applies to protocol version 2 only.

If you don’t have administrative access to the server, you can configure your SSH client to send the alive message to the server instead to achieve the same result. The key here is the ServerAliveInterval option for the SSH client.

You can do this by updating /etc/ssh/ssh_config (applying the setting to every user in the system) or in ~/.ssh/config (single user). Set the following option to have the client send the alive packet every 30 seconds to the server;

ServerAliveInterval 30

The other alternative is to manually set the ServerAliveInterval option every time you’re connecting to a server by using the -o ServerAliveInterval=<time-in-second> prefix as the following example;

$ ssh -o ServerAliveInterval=30 [email protected]

PDF or Portable Document Format the most used and probably the de-facto file format for document exchange. The format was created by Adobe Systems back in 1993 and Adobe Systems produces Adobe Acrobat to create and edit PDF files.

While being the most powerful tool for the purpose, Adobe Acrobat doesn’t currently run natively in Linux. One good alternative for Linux users is PDFEdit.

PDFEdit is the most complete PDFEditor for Linux. It’s QT based and the functions are accessible through theGUI based editor. The editing operations can also be scripted using the ECMAScript.

The program is installable in Ubuntu and Debian with the following command;

$ sudo apt-get install pdfedit

When launched, users can edit PDF files almost the same way as using any other desktop publishing application.

You will get the below error when logging in to phpMyAdmin without password even if your actual MySQL account itself is passwordless. This is because phpMyAdmin is normally configured to disable passwordless login due to security reasons.

To enable passwordless MySQL login in phpMyAdmin, you’ll need to set AllowNoPassword option in phpMyAdmin‘s configuration to TRUE.

To enable the option, uncomment or add the following line;

$cfg['Servers'][$i]['AllowNoPassword'] = TRUE;

Depending on distributions, there could be multiple occurrences of that particular line. Ubuntu for example has the following 2 lines;

if (!empty($dbname)) {
    // other configuration options
    $cfg['Servers'][$i]['AllowNoPassword'] = TRUE;
    // it should be placed before the following line
    $i++;
}

// other configuration options
$cfg['Servers'][$i]['AllowNoPassword'] = TRUE;

Mplayer is initially a movie player for Linux, but through the many available options, it is capable of doing many other things, including to save, record or dump online music stream to file.

In it’s easiest form, running the following command will dump 1.FM’s Channel X (with more channels available from www.shoutcast.com) to current.mp3

$ mplayer -dumpstream http://64.62.252.130:8070  -dumpfile current.mp3

The following bash script takes this a little bit further by keeping the latest 3 dumps, and delete the older ones.

#!/bin/bash
URL=http://64.62.252.130:8070
WORKDIR=/home/shakir/temp/mplayerdump
MAXDUMP=3
CURRENTDUMP=`ls $WORKDIR | wc -l`
 
mv $WORKDIR/current.mp3 $WORKDIR/`date +%F`.mp3
if [ $CURRENTDUMP -ge $MAXDUMP ] ; then
   for i in `ls $WORKDIR | head -n $[($CURRENTDUMP-$MAXDUMP)+1]`; do
      rm $WORKDIR/$i
   done
fi 
 
mplayer -dumpstream  $URL -dumpfile $WORKDIR/current.mp3

Going a little further is to run the script through cron nightly, for daytime listening probably while being mobile and offline. Crontab entry is editable by the following command;

$ crontab -e

and add the following line (assuming the script is located at /home/shakir/mplayerdump.sh)

0 2 * * * /home/shakir/mplayerdump.sh

Do make sure the script is executable by running the following command:

$ chmod a+x /home/shakir/mplayerdump.sh

The basic steps in accessing a MySQL database is normally to connect, execute statement, fetch result, and then to close the connection. The following is the steps translated into Python codes;

# Import required module
import MySQLdb
 
# Connect
conn = MySQLdb.connect(host="localhost", port=3306, user="root", passwd="root123", db="mysql")
cursor = conn.cursor(  )
 
# Execute statement
stmt = "SELECT * FROM user"
cursor.execute(stmt)
 
# Fetch and output the result
result = cursor.fetchall(  )
print result
 
# Close connection
conn.close(  )

The requirement for this is to install the MySQLdb module for Python which is available from it’s project page at http://sourceforge.net/projects/mysql-python. The connect function creates a connection to the database based on the supplied parameters, and a cursor object is then created upon the connection object. The above example only show the execute and fetchall methods, and there many other available methods from the cursor object. The conn object calls the close method to close the connection to the MySQL server.

1. Install the latest Java Runtime Environment.

   # yum install -y java-1.8.0-openjdk

2. Add Elasticsearch repository to yum.
   1. Download and install the public signing key.

      # rpm --import https://artifacts.elastic.co/GPG-KEY-elasticsearch

   2. Add the following lines to /etc/yum.repos.d/elasticsearch.repo.

      [elasticsearch-6.x]
      name=Elasticsearch repository for 6.x packages
      baseurl=https://artifacts.elastic.co/packages/6.x/yum
      gpgcheck=1
      gpgkey=https://artifacts.elastic.co/GPG-KEY-elasticsearch
      enabled=1
      autorefresh=1
      type=rpm-md

3. Install Elasticsearch package along with dependencies.

   # yum install -y elasticsearch

4. Configure Elasticsearch if necessary by editing /etc/elasticsearch/elasticsearch.yml.
5. Configure firewall for Elasticsearch service.
   1. Enable network access to port 9200and 9300.

      # firewall-cmd --permanent --add-port=9200/tcp
      # firewall-cmd --permanent --add-port=9300/tcp

   2. Reload firewall rules and keep state information.

      # firewall-cmd --reload

6. Configure Elasticsearch service to automatically start during boot.

   # systemctl enable elasticsearch

7. Start Elasticsearch service.

   # systemctl start elasticsearch

   The service will take a while to start

8. Test if installation is successful.

   $ curl 127.0.0.1:9200
   {
     "name" : "8v4rGQI",
     "cluster_name" : "elasticsearch",
     "cluster_uuid" : "nkZIqfkpSyCdh_jg3nqWfw",
     "version" : {
       "number" : "6.2.2",
       "build_hash" : "10b1edd",
       "build_date" : "2018-02-16T19:01:30.685723Z",
       "build_snapshot" : false,
       "lucene_version" : "7.2.1",
       "minimum_wire_compatibility_version" : "5.6.0",
       "minimum_index_compatibility_version" : "5.0.0"
     },
     "tagline" : "You Know, for Search"
   }

When plugging an iPhone to a Ubuntu machine for few times, the CPU becomes busy with 100% utilization.

This is due to some bugs which causes iphone-set-info and sometimes gvfs-afc-volume-monitor program to misbehave.

To fix this, run the following commands at the terminal

sudo killall -9 iphone-set-info
sudo killall -9 gvfs-afc-volume-monitor

This will only kill the programs, and will not affect the iPhone’s charging.

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