It's the end of the day on Friday. On your laptop, in an ssh session on a work machine, you check on long.sh, which has been running all day and has another 8...
It's the end of the day on Friday. On your laptop, in an ssh session on a work machine, you check on long.sh, which has been running all day and has another 8 or 9 hours to go. You start to close your laptop. You freeze for a second and groan. This was supposed to be running under a screen session. You know that if you kill the ssh connection, that'll also kill long.sh. What are you going to do? Leave your laptop for the weekend? Kill the job, losing the last 8 hours of work?...
It's the end of the day on Friday. On your laptop, in an ssh session on a work machine, you check on long.sh, which has been running all day and has another 8 or 9 hours to go. You start to close your...
If you run a computer network, be it home WiFi or a global enterprise system, you need a way to investigate the machines connected to your network. When ping...
If you run a computer network, be it home WiFi or a global enterprise system, you need a way to investigate the machines connected to your network. When ping and traceroute won't cut it, you need a port scanner. nmap is the port scanner. It's a powerful, sophisticated tool, not to mention a movie star. The documentation on nmap is voluminous: there's an entire book, with a free online edition, as well as a detailed manpage. In this post I'll show you just a few of the cool...
If you run a computer network, be it home WiFi or a global enterprise system, you need a way to investigate the machines connected to your network. When ping and traceroute won't cut it, you need a...
One year ago, we announced the general availability of Ksplice Uptrack, a subscription service for rebootless kernel updates on Linux. Since then, a lot has...
One year ago, we announced the general availability of Ksplice Uptrack, a subscription service for rebootless kernel updates on Linux. Since then, a lot has happened! Adoption Over 600 companies have deployed Ksplice Uptrack on more than 100,000 production systems, on all 7 continents (Antarctica was the last hold-out). More than 2 million rebootless updates have been installed! You see the greatest system administration time and cost savings when you use Ksplice Uptrack on...
One year ago, we announced the general availability of Ksplice Uptrack, a subscription service for rebootless kernel updates on Linux. Since then, a lot has happened! Adoption Over 600 companies have...
Despite its age, gdb remains an amazingly versatile and flexible tool, and mastering it can save you huge amounts of time when trying to debug problems in your...
Despite its age, gdb remains an amazingly versatile and flexible tool, and mastering it can save you huge amounts of time when trying to debug problems in your code. In this post, I'll share 10 tips and tricks for using GDB to debug most efficiently. I'll be using the Linux kernel for examples throughout this post, not because these examples are necessarily realistic, but because it's a large C codebase that I know and that anyone can download and take a look at. Don't worry...
Despite its age, gdb remains an amazingly versatile and flexible tool, and mastering it can save you huge amounts of time when trying to debug problems in your code. In this post, I'll share 10 tips...
How does coffee shop Internet access work? You pull out your laptop and type http://www.google.com into the URL bar on your browser. Instead of your friendly...
How does coffee shop Internet access work? You pull out your laptop and type http://www.google.com into the URL bar on your browser. Instead of your friendly search box, you get a page where you pay money or maybe watch an advertisement, agree to some terms of service, and are only then free to browse the web. What is going on behind the scenes to give the coffee shop that kind of control over your packets? Let's trace an example of that process from first broadcast to last...
How does coffee shop Internet access work? You pull out your laptop and type http://www.google.com into the URL bar on your browser. Instead of your friendly search box, you get a page where you...
The Linux kernel exposes a wealth of information through the proc special filesystem. It's not hard to find an encyclopedic reference about proc. In this...
The Linux kernel exposes a wealth of information through the proc special filesystem. It's not hard to find an encyclopedic reference about proc. In this article I'll take a different approach: we'll see how proc tricks can solve a number of real-world problems. All of these tricks should work on a recent Linux kernel, though some will fail on older systems like RHEL version 4. Almost all Linux systems will have the proc filesystem mounted at /proc. If you look inside this...
The Linux kernel exposes a wealth of information through the proc special filesystem. It's not hard to find an encyclopedic reference about proc. In this article I'll take a different approach:...
Have you ever had a machine get compromised? What did you do? Did you run rootkit checkers and reboot? Did you restore from backups or wipe and reinstall the...
Have you ever had a machine get compromised? What did you do? Did you run rootkit checkers and reboot? Did you restore from backups or wipe and reinstall the machines, to remove any potential backdoors? In some cases, that may not be enough. In this blog post, we're going to describe how we can gain full control of someone's machine by giving them a piece of hardware which they install into their computer. The backdoor won't leave any trace on the disk, so it won't be...
Have you ever had a machine get compromised? What did you do? Did you run rootkit checkers and reboot? Did you restore from backups or wipe and reinstall the machines, to remove any...
Ever wondered what a .deb file actually is? How is it put together, and what's inside it, besides the data that is installed to your system when you install the...
Ever wondered what a .deb file actually is? How is it put together, and what's inside it, besides the data that is installed to your system when you install the package? Today we're going to break out our sysadmin's toolbox and find out. (While we could just turn to deb(5), that would ruin the fun.) You'll need a Debian-based system to play along. Ubuntu and other derivatives should work just fine. Finding a file to look at Whenever APT downloads a package to install, it...
Ever wondered what a .deb file actually is? How is it put together, and what's inside it, besides the data that is installed to your system when you install the package? Today we're going to break...
Let's talk about how to hijack HTTP traffic on your home subnet using ARP and iptables. It's an easy and fun way to harass your friends, family, or flatmates...
Let's talk about how to hijack HTTP traffic on your home subnet using ARP and iptables. It's an easy and fun way to harass your friends, family, or flatmates while exploring the networking protocols. Please don't experiment with this outside of a subnet under your control -- it's against the law and it might be hard to get things back to their normal state. The setup Significant other comes home from work. SO pulls out laptop and tries to catch up on social media like every...
Let's talk about how to hijack HTTP traffic on your home subnet using ARP and iptables. It's an easy and fun way to harass your friends, family, or flatmates while exploring the networking protocols....
