13 Sep 2016 Matteo Mattei raspberrypi backup
When I backup my raspberry pi SD card one problem I always faced is how much storage space I have to use because using dd command the resulting backup image is exactly the same size of the whole SD card and having memory cards of 32GB or more, the storage of my pc would end pretty soon.
That said I wrote a little script that takes the big image, resize it to the minimal and compress it using gzip.
Just for completeness, this is the command I use to create the image of the SD card:
sudo dd if=/dev/mmcblk0 of=/path/to/image.img bs=1M
Now you can use the following script to shrink the image:
sudo ./raspberrypi_image_resize.sh /path/to/image.img
The process takes some time and at the end you will find that the size of the compressed image is drastically reduced. This is an example of a 8GB SD card before and after the compression:
-rw-r--r-- 1 matteo matteo 8026849280 Sep 10 15:45 image.img
-rw-r--r-- 1 matteo matteo 468097056 Sep 12 12:57 image.img.gz
So from a 8GB file, we have obtained 460MB file.
09 Aug 2016 Matteo Mattei php server security
Attacks through PHP vulnerabilities are very common and every sysadmin should protect and enforce as much as possible the server infrastructure and PHP configuration to prevent as much as possible these types of attack. Today I show you how to tune PHP configuration to disable some dangerous functions and report as less information as possible to outside.
All changes we are going to do are located in php.ini:
expose_php = Off # we don't want to let the clients know we are using PHP
display_errors = Off # in case of error we don't want to show it
register_argc_argv = Off # for better performance
allow_url_fopen = Off # no external URL access
allow_url_include = Off # no external URL access
disable_functions = exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,parse_ini_file,show_source # potential dangerous functions to disable
After that, restart the web server and create a
phpinfo() page to make sure the new values have been correctly set.
09 Aug 2016 Matteo Mattei maldet server web security
The LMD (Linux Malware Detect) also called maldet is a malware scanner developed by (rxfn.com)[https://www.rfxn.com] for Linux released under the GNU GPLv2 license, that is designed around the threats faced in shared hosted environments.
This guide show you how to install, configure and run maldet once a day in a cronjob:
First of all download the latest version of the maldetect, decompress, and install it:
tar -zxvf maldetect-current.tar.gz
Now edit the configuration file /usr/local/maldetect/conf.maldet and set the following values:
The default monitor_mode is used by inotify in case you want real-time protection, otherwise you can relay only on the cronjob that is already configured in /etc/cron.daily.
For real-time protection start maldet inotify monitor:
Now update malware definitions and run your first scan:
maldet -d # update the program
maldet -u # update malware definitions
maldet -a /path/to/scan # scan all files in the path
The last command might take lot of time depending on the number of files to analyze.
09 Aug 2016 Matteo Mattei centos server monitor apache
GoAccess is a nice tool that parses Apache logs and create a report in various format extracting lot of interesting data and statistics. This guide has been tested on CentOS 6.x but it should be very similar also for other distributions.
First of all install some dependencies given we are going to compile the sources:
yum install glib2 glib2-devel glibc make
Download the goaccess source code, copile and install it:
tar xzf goaccess-1.0.2.tar.gz
Now run goaccess and select the format of the Apache log file from the list it proposes. In case you already know how the Apache output file is generated, you can edit the configuration file /usr/local/etc/goaccess.conf with the appropriate patterns for time-format, date-format and log-format. In my case I have the following:
log-format %h %^[%d:%t %^] "%r" %s %b
Create a goaccess folder inside a virtualhost document root (so that it is accessible from the web):
chown myuser.myuser /var/www/vhosts/myhost.com/public_html/goaccess
Now edit /etc/crontab and add a cronjob for goaccess that runs every 10 minutes:
*/10 * * * * myuser /usr/local/bin/goaccess -f /usr/local/apache/logs/access_log -a -d -o /var/www/vhosts/myhost.com/public_html/goaccess/index.html &> /dev/null
Generally is a good idea to protect the goaccess folder with a password so that nobody except you can access and see the statistics of the web server.
cat << EOF > /var/www/vhosts/myhost.com/public_html/goaccess/.htaccess
htpasswd -c /home/myuser/goaccess_htpasswd myuser
Now every 10 minutes the statistics of your Apache (or Nginx) web server are correctly parsed and served in a nice HTML web interface!
09 Aug 2016 Matteo Mattei apache server security
Production Apache web servers need to be well configured for what regards security and performance. Here below a quick tips to make your servers more secure and performant.
First of all you need to verify if you are using prefork module:
apachectl -V | grep -i mpm
If prefork is enabled, you should see a line like this:
If it is, I wrote a simple script to calculate the number of MaxClients your server can support:
Basically this number is calculated with this formula:
(TOTAL_RAM - MYSQL_RAM - 50MB) / APACHE_RAM
So, edit /etc/apache2/apache2.conf on Debian/Ubuntu and /etc/httpd/conf/httpd.conf on RedHat/CentOS and set the prefork section like this:
MaxClients 300 # value calculated
MaxRequestPerChild 3000 # 3000 is a good number, avoid to leave it at 0
Set now some parameters that affects security and performances. Depending on your distribution they can be already set in the following files:
Now test apache configuration and if all goes well, restart the web server:
/etc/init.d/httpd restart # RedHat/CentOS
/etc/init.d/apache2 restart # Debian/Ubuntu