The Helpdesk For I.T. Administrators
If you have a Ubuntu web server (running Ubuntu 14.04 LTS, 13.10, 12.04 LTS, or 10.04 LTS) set up using PHP FPM with Unix sockets, be warned that a recent security patch that fixes an issue with the PHP FPM socket permissions, may also break existing configurations, preventing your website from load php files. After …
The ‘sed’ command can be used to easily replace all occurrences of one string in a text file, with another string. For example: sed -i “s/wordtofind/replacewithword/g” /path/to/file.txt This command will find all occurrences of “wordtofind” and replace them on the fly with “replacewithword” in the file “/path/to/file.txt”. The “-i” command switch specifies to edit the …
To synchronize the time on a Ubuntu computer, with the time from a NTP server, you can simply run the following command: sudo ntpdate 0.pool.ntp.org Replace “0.pool.ntp.org” with your NTP time server of choice. Example output: $ sudo ntpdate 0.pool.ntp.org 1 Jul 00:50:12 ntpdate[31843]: adjust time server 12.34.56.78 offset -0.001309 sec $ Your time will …
The following example pac proxy auto config file will allow you to bypass the proxy server for all local IP addresses, and also set exclusions on specific domain names. For information on what a PAC file is, please check out: What is a .pac proxy auto config file Advanced .PAC proxy …
A .pac (Proxy Auto Config) file is a file stored on a web server that contains instructions for the browser, to help automate the proxy server setting configuration in a web browser. The .pac proxy configuration file contains JavaScript code, and must contain one function called FindProxyForURL. This function accepts two parameters, a URL, and …
To change the timezone on Ubuntu all you need to do is reconfigure the tzdata package. This can be done using the following command: sudo dpkg-reconfigure tzdata A menu prompt will then appear. Simply enter in your geographic area, and then the relevant city/timezone you want.
SSH allows the use of encryption keys to be used to allow logging into a system instead of having to remember a plain text password. This is great for use in scripts, and automated tasks, but can be a problem is anyone else ever gets the keys somehow. If the keys become compromised, you must …
DNS amplification attacks are a common form of DDoS that makes used of misconfigured DNS servers on the internet. The attack involves sending a request to the misconfigured DNS server, with a spoofed source IP address, so the response goes back to a third party (the target/victim). The attacker will use the largest DNS query …
The dig DNS lookup utility is a handy tool for performing DNS queries. The dig utility is part of the bind utilities package in CentOS. The following command can be used to install dig. Install dig (the bind-utils package): # yum install bind-utils Note: Make sure you run the above command as a user with …
This howto guide outlines the steps to enable IP forwarding on Ubuntu 13.04. This is required if you want your system to act as a router. Check the current setting: $ sysctl net.ipv4.ip_forward This should output a 0 or a 1 depending on if it is already enabled or not. eg: the following shows where …