Sysadmin 101: Alerting

This is the first in a series of articles on system administrator fundamentals. These days, DevOps has made even the job title "system administrator" seem a bit archaic, much like the "systems analyst" title it replaced. These DevOps positions are rather different from typical sysadmin jobs in the past in that they have a much larger emphasis on software development far beyond basic shell scripting. As a result, they often are filled with people with software development backgrounds without much prior sysadmin experience. In the past, sysadmins would enter the role at a junior level and be mentored by a senior sysadmin on the team, but in many cases currently, companies go quite a while with cloud outsourcing before their first DevOps hire. As a result, DevOps engineers might be thrust into the role at a junior level with no mentor around apart from search engines and Stack Overflow posts. In this series of articles, I'm going to expound on some of the lessons I've learned through the years that might be obvious to longtime sysadmins but may be news to someone just coming into this position.

In this first article, I cover on-call alerting. Like with any job title, the responsibilities given to sysadmins, DevOps and Site Reliability Engineers may differ, and in some cases, they may not involve any kind of 24x7 on-call duties, if you're lucky. For everyone else, though, there are many ways to organize on-call alerting, and there also are many ways to shoot yourself in the foot.

The main enemies of on-call alerting are false positives, with the main risks being ignoring alerts or burnout for members of your team. This article talks about some best practices you can apply to your alerting policies that hopefully will reduce burnout and make sure alerts aren't ignored.

Alert Thresholds

A common pitfall sysadmins run into when setting up monitoring systems is to alert on too many things. These days, it's simple to monitor just about any aspect of a server's health, so it's tempting to overload your monitoring system with all kinds of system checks. One of the main ongoing maintenance tasks for any monitoring system is setting appropriate alert thresholds to reduce false positives. This means the more checks you have in place, the higher the maintenance burden. As a result, I have a few different rules I apply to my monitoring checks when determining thresholds for notifications.

Critical alerts must be something I want to be woken up about at 3am.

A common cause of sysadmin burnout is being woken up with alerts for systems that don't matter. If you don't have a 24x7 international development team, you probably don't care if the build server has a problem at 3am, or even if you do, you probably are going to wait until the morning to fix it. By restricting critical alerts to just those systems that must be online 24x7, you help reduce false positives and make sure that real problems are addressed quickly.

Critical alerts must be actionable.

Some organizations send alerts when just about anything happens on a system. If I'm being woken up at 3am, I want to have a specific action plan associated with that alert so I can fix it. Again, too many false positives will burn out a sysadmin that's on call, and nothing is more frustrating than getting woken up with an alert that you can't do anything about. Every critical alert should have an obvious action plan the sysadmin can follow to fix it.

Warning alerts tell me about problems that will be critical if I don't fix them.

There are many problems on a system that I may want to know about and may want to investigate, but they aren't worth getting out of bed at 3am. Warning alerts don't trigger a pager, but they still send me a quieter notification. For instance, if load, used disk space or RAM grows to a certain point where the system is still healthy but if left unchecked may not be, I get a warning alert so I can investigate when I get a chance. On the other hand, if I got only a warning alert, but the system was no longer responding, that's an indication I may need to change my alert thresholds.

Repeat warning alerts periodically.

I think of warning alerts like this thing nagging at you to look at it and fix it during the work day. If you send warning alerts too frequently, they just spam your inbox and are ignored, so I've found that spacing them out to alert every hour or so is enough to remind me of the problem but not so frequent that I ignore it completely.

Everything else is monitored, but doesn't send an alert.

There are many things in my monitoring system that help provide overall context when I'm investigating a problem, but by themselves, they aren't actionable and aren't anything I want to get alerts about. In other cases, I want to collect metrics from my systems to build trending graphs later. I disable alerts altogether on those kinds of checks. They still show up in my monitoring system and provide a good audit trail when I'm investigating a problem, but they don't page me with useless notifications.

Kyle's rule.

One final note about alert thresholds: I've developed a practice in my years as a sysadmin that I've found is important enough as a way to reduce burnout that I take it with me to every team I'm on. My rule is this:

If sysadmins were kept up during the night because of false alarms, they can clear their projects for the next day and spend time tuning alert thresholds so it doesn't happen again.

There is nothing worse than being kept up all night because of false positive alerts and knowing that the next night will be the same and that there's nothing you can do about it. If that kind of thing continues, it inevitably will lead either to burnout or to sysadmins silencing their pagers. Setting aside time for sysadmins to fix false alarms helps, because they get a chance to improve their night's sleep the next night. As a team lead or manager, sometimes this has meant that I've taken on a sysadmin's tickets for them during the day so they can fix alerts.


Sending an alert often is referred to as paging or being paged, because in the past, sysadmins, like doctors, carried pagers on them. Their monitoring systems were set to send a basic numerical alert to the pager when there was a problem, so that sysadmins could be alerted even when they weren't at a computer or when they were asleep. Although we still refer to it as paging, and some older-school teams still pass around an actual pager, these days, notifications more often are handled by alerts to mobile phones.

The first question you need to answer when you set up alerting is what method you will use for notifications. When you are deciding how to set up pager notifications, look for a few specific qualities.

Something that will alert you wherever you are geographically.

A number of cool office projects on the web exist where a broken software build triggers a big red flashing light in the office. That kind of notification is fine for office-hour alerts for non-critical systems, but it isn't appropriate as a pager notification even during the day, because a sysadmin who is in a meeting room or at lunch would not be notified. These days, this generally means some kind of notification needs to be sent to your phone.

An alert should stand out from other notifications.

False alarms can be a big problem with paging systems, as sysadmins naturally will start ignoring alerts. Likewise, if you use the same ringtone for alerts that you use for any other email, your brain will start to tune alerts out. If you use email for alerts, use filtering rules so that on-call alerts generate a completely different and louder ringtone from regular emails and vibrate the phone as well, so you can be notified even if you silence your phone or are in a loud room. In the past, when BlackBerries were popular, you could set rules such that certain emails generated a "Level One" alert that was different from regular email notifications.

The BlackBerry days are gone now, and currently, many organizations (in particular startups) use Google Apps for their corporate email. The Gmail Android application lets you set per-folder (called labels) notification rules so you can create a filter that moves all on-call alerts to a particular folder and then set that folder so that it generates a unique alert, vibrates and does so for every new email to that folder. If you don't have that option, most email software that supports multiple accounts will let you set different notifications for each account so you may need to resort to a separate email account just for alerts.

Something that will wake you up all hours of the night.

Some sysadmins are deep sleepers, and whatever notification system you choose needs to be something that will wake them up in the middle of the night. After all, servers always seem to misbehave at around 3am. Pick a ringtone that is loud, possibly obnoxious if necessary, and also make sure to enable phone vibrations. Also configure your alert system to re-send notifications if an alert isn't acknowledged within a couple minutes. Sometimes the first alert isn't enough to wake people up completely, but it might move them from deep sleep to a lighter sleep so the follow-up alert will wake them up.

While ChatOps (using chat as a method of getting notifications and performing administration tasks) might be okay for general non-critical daytime notifications, they are not appropriate for pager alerts. Even if you have an application on your phone set to notify you about unread messages in chat, many chat applications default to a "quiet time" in the middle of the night. If you disable that, you risk being paged in the middle of the night just because someone sent you a message. Also, many third-party ChatOps systems aren't necessarily known for their mission-critical reliability and have had outages that have spanned many hours. You don't want your critical alerts to rely on an unreliable system.

Something that is fast and reliable.

Your notification system needs to be reliable and able to alert you quickly at all times. To me, this means alerting is done in-house, but many organizations opt for third parties to receive and escalate their notifications. Every additional layer you can add to your alerting is another layer of latency and another place where a notification may be dropped. Just make sure whatever method you choose is reliable and that you have some way of discovering when your monitoring system itself is offline.

In the next section, I cover how to set up escalations—meaning, how you alert other members of the team if the person on call isn't responding. Part of setting up escalations is picking a secondary, backup method of notification that relies on a different infrastructure from your primary one. So if you use your corporate Exchange server for primary notifications, you might select a personal Gmail account as a secondary. If you have a Google Apps account as your primary notification, you may pick SMS as your secondary alert.

Email servers have outages like anything else, and the goal here is to make sure that even if your primary method of notifications has an outage, you have some alternate way of finding out about it. I've had a number of occasions where my SMS secondary alert came in before my primary just due to latency with email syncing to my phone.

Create some means of alerting the whole team.

In addition to having individual alerting rules that will page someone who is on call, it's useful to have some way of paging an entire team in the event of an "all hands on deck" crisis. This may be a particular email alias or a particular key word in an email subject. However you set it up, it's important that everyone knows that this is a "pull in case of fire" notification and shouldn't be abused with non-critical messages.

Alert Escalations

Once you have alerts set up, the next step is to configure alert escalations. Even the best-designed notification system alerting the most well intentioned sysadmin will fail from time to time either because a sysadmin's phone crashed, had no cell signal, or for whatever reason, the sysadmin didn't notice the alert. When that happens, you want to make sure that others on the team (and the on-call person's second notification) is alerted so someone can address the alert.

Alert escalations are one of those areas that some monitoring systems do better than others. Although the configuration can be challenging compared to other systems, I've found Nagios to provide a rich set of escalation schedules. Other organizations may opt to use a third-party notification system specifically because their chosen monitoring solution doesn't have the ability to define strong escalation paths. A simple escalation system might look like the following:

  • Initial alert goes to the on-call sysadmin and repeats every five minutes.

  • If the on-call sysadmin doesn't acknowledge or fix the alert within 15 minutes, it escalates to the secondary alert and also to the rest of the team.

  • These alerts repeat every five minutes until they are acknowledged or fixed.

The idea here is to give the on-call sysadmin time to address the alert so you aren't waking everyone up at 3am, yet also provide the rest of the team with a way to find out about the alert if the first sysadmin can't fix it in time or is unavailable. Depending on your particular SLAs, you may want to shorten or lengthen these time periods between escalations or make them more sophisticated with the addition of an on-call backup who is alerted before the full team. In general, organize your escalations so they strike the right balance between giving the on-call person a chance to respond before paging the entire team, yet not letting too much time pass in the event of an outage in case the person on call can't respond.

If you are part of a larger international team, you even may be able to set up escalations that follow the sun. In that case, you would select on-call administrators for each geographic region and set up the alerts so that they were aware of the different time periods and time of day in those regions, and then alert the appropriate on-call sysadmin first. Then you can have escalations page the rest of the team, regardless of geography, in the event that an alert isn't solved.

On-Call Rotation

During World War One, the horrors of being in the trenches at the front lines were such that they caused a new range of psychological problems (labeled shell shock) that, given time, affected even the most hardened soldiers. The steady barrage of explosions, gun fire, sleep deprivation and fear day in and out took its toll, and eventually both sides in the war realized the importance of rotating troops away from the front line to recuperate.

It's not fair to compare being on call with the horrors of war, but that said, it also takes a kind of psychological toll that if left unchecked, it will burn out your team. The responsibility of being on call is a burden even if you aren't alerted during a particular period. It usually means you must carry your laptop with you at all times, and in some organizations, it may affect whether you can go to the movies or on vacation. In some badly run organizations, being on call means a nightmare of alerts where you can expect to have a ruined weekend of firefighting every time. Because being on call can be stressful, in particular if you get a lot of nighttime alerts, it's important to rotate out sysadmins on call so they get a break.

The length of time for being on call will vary depending on the size of your team and how much of a burden being on call is. Generally speaking, a one- to four-week rotation is common, with two-week rotations often hitting the sweet spot. With a large enough team, a two-week rotation is short enough that any individual member of the team doesn't shoulder too much of the burden. But, even if you have only a three-person team, it means a sysadmin gets a full month without worrying about being on call.

Holiday on call.

Holidays place a particular challenge on your on-call rotation, because it ends up being unfair for whichever sysadmin it lands on. In particular, being on call in late December can disrupt all kinds of family time. If you have a professional, trustworthy team with good teamwork, what I've found works well is to share the on-call burden across the team during specific known holiday days, such as Thanksgiving, Christmas Eve, Christmas and New Year's Eve. In this model, alerts go out to every member of the team, and everyone responds to the alert and to each other based on their availability. After all, not everyone eats Thanksgiving dinner at the same time, so if one person is sitting down to eat, but another person has two more hours before dinner, when the alert goes out, the first person can reply "at dinner", but the next person can reply "on it", and that way, the burden is shared.

If you are new to on-call alerting, I hope you have found this list of practices useful. You will find a lot of these practices in place in many larger organizations with seasoned sysadmins, because over time, everyone runs into the same kinds of problems with monitoring and alerting. Most of these policies should apply whether you are in a large organization or a small one, and even if you are the only DevOps engineer on staff, all that means is that you have an advantage at creating an alerting policy that will avoid some common pitfalls and overall burnout.

Kyle Rankin is a Tech Editor and columnist at Linux Journal and the Chief Security Officer at Purism. He is the author of Linux Hardening in Hostile Networks, DevOps Troubleshooting, The Official Ubuntu Server Book, Knoppix Hacks, Knoppix Pocket Reference, Linux Multimedia Hacks and Ubuntu Hacks, and also a contributor to a number of other O'Reilly books. Rankin speaks frequently on security and open-source software including at BsidesLV, O'Reilly Security Conference, OSCON, SCALE, CactusCon, Linux World Expo and Penguicon. You can follow him at @kylerankin.

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