In a previous article I discussed how to use Mailgun as a relay in Postfix. This works great if you are only sending email from one website on your server, often times however you will have multiple websites sending email on a single server. In these cases, websites NOT belonging to the sender domain will … [Read more…]
Using multiple monitors on my Linux laptop has introduced a couple of unique issues. The largest of which is that the laptop seems to forget my monitor configuration every time I unplug it. This article is going to discuss how I addressed this problem and how I spanned my desktop wallpaper. But first, a bit … [Read more…]
When parsing log files sed is not the go-to tool for most techs, but it offers a pretty neat feature: the ability to easily search a log file for a specific date/time range. Pattern Matching sed -n ‘/Dec 30 13:00/p’ /var/log/messages Date Range Matching sed -n ‘/Dec 30 13:00/,/Dec 30 14:00/p’ /var/log/messages Change Delimiters If … [Read more…]
Inevitably every Linux administrator will eventually have to alter permissions and owerships, perhaps even FACLs. But what happens when your changes go awry? The problem is amplified if you were making changes recursively! Backup Permissions Fortunately there is a pretty simple method to backup the permissions, ownerships, and FACLs: getfacl -pR /path/to/backup > /root/perms.bak NOTE: … [Read more…]
Bind mounts in Linux allow you to mount one part of the file hierarchy somewhere else. I highly recommend using bind mounts in chrooted environment as it can simplify user access control. Creating Bind Mounts Bind mounts were added in kernel 2.4.0, so older systems will not support it. Run uname -r to verify your … [Read more…]
File transfer is a fundamental concept of the Internet, however there are a plethora of configuration options that often lead to confusion. In this article I am going to discuss installation and configuration of FTP, FTPS, and SFTP as well as how to chroot (i.e. jail) users for these services. FTP, The Basics FTP is … [Read more…]
I tend to spend quite a bit of my time on a command line, so I am always looking for little ways to make my life easier. Because of that, this post will be a bit of a living document that I plan to occasionally update as I discover more handy tricks. This is not … [Read more…]
Over the last couple of days I have become increasingly interested in unraveling the mysteries behind establishing an SSH connection. The process is very intricate and some of the documentation seems scattered, so I decided to write a bit about it in the hopes that someone else may benefit. Prior to writing this article I … [Read more…]
Mailgun is a developer-centric approach to email. It can be used to simply relay email, but it can do so much more! In this article I am going to discuss basic configuration for using Mailgun as a relay with Postfix and briefly discuss some of the additional features offered by Mailgun. Step 1) Account creation … [Read more…]
An often underused feature of OpenSSH is the Match statement. Match statements work on OpenSSH 4.4+; applicable versions ship with RHEL/CentOS 6+ and Ubuntu 12.04+. The Match directive accepts the following options: Match User Match Group Match Host Match LocalAddress Match LocalPort Match Address Match statements can be used to help harden SSH but can … [Read more…]