Say Goodbye to Reboots with Ksplice

Everyone hates rebooting for updates. When system administrators reboot their servers, they have to manage an inconvenient outage window—quite possibly during the middle of the night—and they have to deal with the lost productivity and annoyed users that result from the disruption. Similarly, rebooting your desktop means losing all of your valuable state—your favorite editor with the 35 open files you were working on, your 14 terminals, and, of course, your paused game of Frozen Bubble.

But the alternative—not installing updates right away—is even more unpleasant. If your parents were anything like mine, they insisted that you do two things: eat your vegetables and install your software updates. Why? Well, first, vegetables provide your body with much-needed nutrients. Second, most exploits take advantage of well-known software vulnerabilities—vulnerabilities that do not exist on patched systems. So staying up to date goes a long way in keeping your systems secure and reliable.

So is this it? Will we forever be forced to choose between security and availability? Fortunately, the answer is no. Ksplice, a startup company founded by MIT alumni, has developed technology that can install software updates, without requiring a reboot.

Using this technology, they are offering Ksplice Uptrack, a service that keeps your Linux systems up to date and secure without any hassle. Additionally, experienced kernel developers also can use the Ksplice tools to create their own rebootless updates.

You can start using Ksplice Uptrack without any advance preparation. Follow the directions on the Ksplice Uptrack Web site, which allows you to install the software using your package manager.

Once you've done this, a K icon appears in your notification area. When you see the K, you know that you have the latest security fixes for your Linux kernel. When new updates are available, a warning sign appears over the K.

Figure 1. Ksplice Uptrack notifies you that new rebootless updates are available by displaying a K with a warning sign in the notification area.

When this happens, click on the K to view a list of the available updates. Install the updates by clicking the green Install all updates button. The listed updates will be installed on your running system in seconds, as your applications continue to run without interruption.

Figure 2. The Ksplice Uptrack manager shows you a list of the available kernel updates. These updates correct security and reliability problems in the kernel. You can install these updates, without disrupting your running applications, by clicking Install all updates.

Like any good Linux tool, Ksplice Uptrack also can be controlled from the command line, with four simple commands. Each update has an ID associated with it, which you use to name it. You can install or remove individual updates, just like with any package manager. Here are the Ksplice Uptrack Commands:

What about when you actually do reboot? Well, you can boot in to your brand-new kernel that you've installed the traditional way, using your package manager. Everything will continue to work nicely, and when Ksplice Uptrack detects new updates for this kernel, it will notify you, just like before.

Alternatively, you can reboot into your old kernel. In this case, Ksplice Uptrack will re-apply the rebootless updates early in the boot process. This approach may be more desirable for some system administrators, because it ensures that the machine is in the exact same configuration both before and after the reboot.

New research originally conducted at MIT makes this rebootless update software possible. Three basic actions are related to rebootless updates: creating a rebootless update from a source code patch, applying a rebootless update to a running system and reversing an update. I describe each of these actions below.

To follow along with these examples on your own computer, you need to install the Ksplice utilities. Your distribution likely already includes these utilities, so you can install them using your package manager. If not, you can download them from the Ksplice Web site.