1495: Hard Reboot

2015-03-06T10:21:38Z

Smangano: /* Explanation */

{{comic
| number = 1495
| date = March 6, 2015
| title = Hard Reboot
| image = hard_reboot.png
| titletext = Googling inevitably reveals that my problem is caused by a known bug triggered by doing [the exact combination of things I want to do]. I can fix it, or wait a few years until I don't want that combination of things anymore, using the kitchen timer until then.
}}

==Explanation==
This comic is about using a simple and unrelated trick to fix a problem.

{{w|Paging|Swap space}} is an area of a computer's hard drive reserved for use when the computer runs out of RAM. Ideally, RAM + SWAP >= MAX, where MAX is the amount of memory the computer will ever try to use at the same time. However, some [broken] programs may keep requesting memory from the system until computer runs out of resources. Alternatively, system may be misconfigured to run more and more programs simultaneously. Rebooting the computer will empty the RAM and swap space so resources can be reallocated, but this only temporarily alleviates the underlying issue. Determining the root cause of the problem is often nontrivial.

It would take up to 10 hours to figure out why the server is running out of swap space and fix the problem. Alternatively, Randall could just take 5 minutes and plug the server into a light timer. This attitude to problem solving is in contrast to the attitude shown in [[974: The General Problem]].

Timers [http://www.diytrade.com/china/pd/10081499/Analog_Electric_Light_on_off_Timer_Dual_Outlet_Switch.html like the one in the comic] typically have four switches or notches per hour, so using the timer would replace an unpredictable and indefinite loss of service with a regular 15 minute downtime event once a day. Also, it can be scheduled during, say, the middle of the night when most users are sleeping to minimize disruption.

The correct method of scheduling a regular reboot would be using a ''cron'' task, but perhaps the server is "crashing" in such a dramatic manner that ''cron,'' or ''shutdown,'' or ''init'' stops working. The comic title alludes to this, in that a "hard" reboot scheduled with an analog timer is more guaranteed to work than a "soft" one scheduled with ''cron.''

If a memory leak is not present, the problem might be fixable by simply increasing swap space, however if there is a more complex underlying issue, this is the first step along the path of 10 hours of troubleshooting. As a general stereotype, the type of person who has a home server is probably also the kind of person who would start by 'just' increasing the swap size, and before they know it has spent 10 hours completely engrossed in the challenge of fixing the problem. (See [[349: Success]])

The title text's first sentence refers to situations where the given solution to a problem is just the original problem rephrased to sound like a solution. It may also refer to bug trackers, where someone found out and posted what causes the issue, but the bug is marked as "Unresolved," "Waiting," or "Will not fix."

The title text's second sentence is about the human tendency to wait on someone else to fix a problem rather than doing it yourself. Since everyone is waiting on someone else to do it, such problems tend to never be fixed, hence the solution of "wait[ing] a few years until I don't want that combination of things anymore."

==Transcript==
''A section of a screen with a white-on-black color scheme is shown. The screen is covered in lines of illegible text.''

Figuring out why my home server keeps running out of swap space and crashing: 1-10 hours

''Next to the section of the screen is a timer plugged into a power port with cable running off to the side.''

Plugging it into a light timer so it reboots every 24 hours: 5 minutes

'''Why everything I have is broken'''

{{comic discussion}}

explain xkcd - User contributions [en]

1495: Hard Reboot