Programs compiled for Linux normally use shared libraries rather than being statically linked. The advantage to this is that it’ll save disk spaces as programs don’t need to include libraries in their package. The disadvantage to this is that a program compiled for one system, might not work on another system (distribution) as libraries might not be identically configured on different systems.

The program ldd can be used to display shared libraries used by a program, along with the path of where the library is expected to be found in the filesystem.

The following example shows dependencies of the program bash in a 64 bit machine:

$ ldd /bin/bash
linux-vdso.so.1 =>  (0x00007fff8a372000)
        libncurses.so.5 => /lib/libncurses.so.5 (0x00007fa53a974000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fa53a770000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fa53a3db000)
        /lib64/ld-linux-x86-64.so.2 (0x00007fa53abe2000)

To display more information and to not need to type the program’s full path, run the command as the following.

$ ldd -v `which bash`
        linux-vdso.so.1 =>  (0x00007fff855ff000)
        libncurses.so.5 => /lib/libncurses.so.5 (0x00007f0cc4c11000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f0cc4a0d000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f0cc4678000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f0cc4e7f000)

        Version information:
        /bin/bash:
                libdl.so.2 (GLIBC_2.2.5) => /lib/x86_64-linux-gnu/libdl.so.2
                libc.so.6 (GLIBC_2.4) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.8) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.3) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.11) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.3.4) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.2.5) => /lib/x86_64-linux-gnu/libc.so.6
        /lib/libncurses.so.5:
                libdl.so.2 (GLIBC_2.2.5) => /lib/x86_64-linux-gnu/libdl.so.2
                libc.so.6 (GLIBC_2.4) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.3) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.3.4) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.2.5) => /lib/x86_64-linux-gnu/libc.so.6
        /lib/x86_64-linux-gnu/libdl.so.2:
                ld-linux-x86-64.so.2 (GLIBC_PRIVATE) => /lib64/ld-linux-x86-64.so.2
                libc.so.6 (GLIBC_PRIVATE) => /lib/x86_64-linux-gnu/libc.so.6
                libc.so.6 (GLIBC_2.2.5) => /lib/x86_64-linux-gnu/libc.so.6
        /lib/x86_64-linux-gnu/libc.so.6:
                ld-linux-x86-64.so.2 (GLIBC_PRIVATE) => /lib64/ld-linux-x86-64.so.2
                ld-linux-x86-64.so.2 (GLIBC_2.3) => /lib64/ld-linux-x86-64.so.2

Link building or the process of getting backlinks to your website is very important because other than to increase referral traffic to your site, it’ll also increase search engine traffic by increasing your site’s PageRank. Link building is therefore the most important step in increasing your website’s traffic.

tar.bz2 is a file format for bzip2-compressed tar archive. tar.bz2 files are normally small in size but require more CPU power to compress and extract as compared to tar.gz files.

To view the content of a tar.bz2 file without uncompressing, use tar with the tf options as follows;

$ tar tf filename.tar.bz2

The command will produce a list of files contained in the archive. Use less if the list is too long;

$ tar tf filename.tar.bz2 | less

httpd.conf is Apache‘s main configuration file by default. It will then call out other files and directories via Include and IncludeOptional directives which is meant to simplify the main configuration file, and the structure wildly varies between platforms.

httpd.conf itself is located differently between platforms. These are some of the known locations;

If your platform of choice is not on the list, simply run httpd -V from the terminal and look for SERVER_CONFIG_FILE.

# httpd -V
Server version: Apache/2.4.25 (Unix)
Server built:   Feb  6 2017 20:02:10
Server's Module Magic Number: 20120211:67
Server loaded:  APR 1.5.2, APR-UTIL 1.5.4
Compiled using: APR 1.5.2, APR-UTIL 1.5.4
Architecture:   64-bit
Server MPM:     prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_FLOCK_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=256
 -D HTTPD_ROOT="/usr"
 -D SUEXEC_BIN="/usr/bin/suexec"
 -D DEFAULT_PIDLOG="/private/var/run/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="/private/etc/apache2/mime.types"
 -D SERVER_CONFIG_FILE="/private/etc/apache2/httpd.conf"

# httpd -V | grep SERVER_CONFIG_FILE
 -D SERVER_CONFIG_FILE="/private/etc/apache2/httpd.conf"

There are many Google AdSense success stories that can be found on the Internet, but for most people joining the program, they are far from being successful. Average Google AdSense publisher’s earning can barely pay for their website hosting, let alone to getting rich by it.

Many sites and tutorial make it sound too easy to earn big from Google AdSense. While it is true that it’s easy to sign up for the program and to earn from it, earning enough to actually make a living out of it sounds like just a dream.

This article tries to be realistic about making money online, particularly with Google AdSense. The following are some tips on how to be successful with the program.

Maximum upload file size for PHP is bound to the lowest value of both post_max_size and upload_max_filesize directives in your configuration. post_max_size affects maximum file upload size as file upload is normally an HTTP POST operation.

You can update your PHP configuration file for these two directives to the values that fit your requirement and then restart your web server.

The following example allows for file upload of not more than 200MB.

post_max_size = 200M
upload_max_filesize = 250M

Alternatively, you can add the following lines in your .htaccess and the setting will apply to scripts from within the .htaccess‘ directory.

php_value upload_max_filesize 200M
php_value post_max_size 250M

Restart Apache for the changes to take effect.

You won’t be able to directly use your PuTTY‘s key in Linux‘s OpenSSH because the keys are of different format. You’ll need to first convert PuTTY‘s key to OpenSSH‘s key format by following these steps;

1. Download PuTTY Key Generator (puttygen.exe) from the following URL

   https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html

2. Launch the program and click on the Load button and select your PuTTY‘s key file, which normally ends with .ppk extension.
   
   
3. Enter the key’s passphrase if prompted.
   
4. Details of the imported key will be displayed.
   
5. Go to Conversions → Export OpenSSH key from the menu.
   
6. Save your converted key to a new file and location.
   

Apache‘s reverse proxy is an act of an Apache webserver providing content from other webserver transparently. This is useful in many instances such as caching and mirroring, but it’s mostly used to serve websites that are hosted behind NAT or a firewall. A reverse proxy server routes connection addressed to the internal server, and the client sees the reverse proxy server itself as the origin server.

For example, Apache can be configured to serve URL‘s such as http://www.example.com/webapp to actually get the content from http://192.168.0.10/myapp, which is hosted from an internal network. This happens transparently and the user initially requesting http://www.example.com/webapp need not to be aware of what happens in the background.

Being the language used in website designs, CSS is one of the language supported by Vim’s auto-complete feature.

To start using the feature, enter the following while in Vim’s command mode.

:set omnifunc=csscomplete#CompleteCSS

That will enable CSS auto-completion in Vim. To use it, press Ctrl + x followed by Ctrl + o while partially typing CSS codes.

The following is a sample screenshot.

You can use the arrow key to navigate through the list to choose your desired auto-complete suggestion.

The easiest way to shutdown a Windows machine from Linux is by using Samba’s net command. The following command will send an RPC call to the Windows machine, telling it to shutdown;

$ net rpc SHUTDOWN -C "Comment here" -f -I xxx.xxx.xxx.xxx -U username%password

If successful, we’ll be presented with the following mesage;

Shutdown of remote machine succeeded

Change “Comment here” with whatever shutdown comment that you would like for the shutdown, and replace xxx.xxx.xxx.xxx with the IP address of the Windows machine that we are to shutdown. A valid username and password also need to be supplied as a parameter to the the -U switch.

For this command to be successful, the user we use must have shutdown privilege on the windows machine. The Windows machine also need to have RPC enabled, and no firewall is blocking port 135 as the port used by RPC. The net command itself however is only available if Samba is installed.