Apache webserver reads its configuration files every time it's started. The configuration files are in plain text format, and Apache will need to restart every time there are changes …
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Privacy Policy for onlineweb.tools

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PHP scripts are only allocated a certain amount of memory that it can use, and whet it reaches the limit, it will produce the following error;

PHP Fatal error: Allowed memory size of xxxx bytes exhausted (tried to allocate yyyy) in yourscript.php

To fix this, you’ll need to increase the memory limit for PHP scripts using any of the following methods;

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

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"

shakir@anduril:~/Dropbox/Workspace/Apache/mirror/oseems.com$ sudo vi /etc/mysql/my.cnf
shakir@anduril:~/Dropbox/Workspace/Apache/mirror/oseems.com$ sudo /etc/init.d/apparmor restart
* Reloading AppArmor profiles
Skipping profile in /etc/apparmor.d/disable: usr.bin.firefox
Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd

 ...done.

shakir@anduril:~/Dropbox/Workspace/Apache/mirror/oseems.com$ sudo vi /etc/apparmor.d/usr.sbin.mysqld
shakir@anduril:~/Dropbox/Workspace/Apache/mirror/oseems.com$ sudo /etc/init.d/apparmor restart
* Reloading AppArmor profiles
Skipping profile in /etc/apparmor.d/disable: usr.bin.firefox
Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd

 ...done.

shakir@anduril:~/Dropbox/Workspace/Apache/mirror/oseems.com$ sudo /etc/init.d/mysql restart
* Stopping MySQL database server mysqld

 ...done.

* Starting MySQL database server mysqld

 ...done.

* Checking for tables which need an upgrade, are corrupt or were
not closed cleanly.

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.