Friday, December 16, 2016

How to safely kill your NTP server

NTP is that service that typically quietly runs in the background on almost every single computer in the world. When a computer boots up for the first time, NTP gets configured and is almost never considered again. Why? Because for most people, it just works. Until the end of this century (Y2K + 100) or the next leap year second, most system administrators will happily not need to think about the wonders that NTP gives us.  There are, of course, always security considerations to make, but again, once those are addressed, NTP again fades to the back of your mind. 

If you are running your servers in Amazon, it's possible that your VPC doesn't permit access to external NTP peers. In this case, you may follow directions to set up your own NTP server. These were the exact directions my sys admin predecessor followed for the VPC I inherited at my current job. 

As it turns out, every one of the servers in our VPC needs external internet access and we configure that to route through a NAT. So, other than the security considerations of allowing traffic over port 123, there was no good reason to not rely on the public NTP peers. Great! So, that meant we could kill our internal NTP and save time and money by not hosting it.

So, how do you safely stop and shutdown your NTP server?

First up, the basics:
  1. Run a loop across all your servers and `grep 'server' /etc/ntp.conf | grep <ip|name>`. I just used a bash for-loop. 
    1. If you have any matches. Use a similar bash loop to replace the conf file and `sudo service ntpd stop; sudo service ntpd stop`. 
    2. Then run `ntpq -p` to confirm connections could be established with upstream peers.
  2. Check your image and the scripts that build them. If necessary, rebuild those.

Now you can feel pretty confident that everything you know about is configured properly. ...but what about what you don't know about?? Here's what I did:

  1. ssh ntp-server
  2. sudo service ntpd stop
  3. screen
  4. sudo nc -vulk -w 1 123
This sets up a dumb netcat UDP listener on NTP port 123. It will log all connections to the console. The `-w 1` is the only way I could contrive prevent the first connection from commandeering the process. It will time out the connection after 1 second; then combined with `-k`, it will keep listening for new connections. The screen is simply for the safety of knowing that this will keep running when I close my laptop, a.k.a. screen daemon. 

Let this run for a day and if you see any traffic in there, you'll know the IP address of the server trying to get at you for NTP info.

Tuesday, July 12, 2016

git log exit code 141?

Something's that been bugging me for a while now is that when I do a `git log` command and quit before scrolling through all the output, my terminal prompt shows my last command (the git log) exited non-zero with status code 141.

I have git configured to use `less -+S` as the pager.

The answer turns out to be really straightforward, but took me a little bit of internet searching. I am capturing the learning here to save my future self the research and possibly anyone else typing the exact same thing into Google that I did ;-)

The explanation:

  • Git pipes the logs into less
  • I quit the less process, which sends a SIGPIPE signal (13) to the underlying git process streaming the logs
  • git catches the interrupt and exits prematurely and per POSIX convention returns 128 + the SIGPIPE status ==> 141 to indicate that it was terminated by signal 13
The background:

Thursday, June 2, 2016

Yes, git, I did mean that

Git comes out of the box with a nice "auto correct" feature, but sometimes it's not correct. And other times, the first suggestion isn't the one you intended, but the second or third.

Here's a short, fun shell function (tested in zsh and bash) that will run your last git command and figure out what you meant to do and then run it for you.

Parity with auto-correct

$ git dif
git: 'dfif' is not a git command. See 'git --help'.

Did you mean this?
> idid !!
<shows diff>

Choose non-default auto-correct suggestion

$ git pu
git: 'pu' is not a git command. See 'git --help'.

Did you mean one of these?

$ idid -2 !!
<runs git push>

Thursday, May 19, 2016

Starting an Open Source Office within your Company

I had the privilege of sharing the stage yesterday with other members of the TODO Group to share our reflections from running Open Source Offices within our respective companies. See the post on the TODO blog.

In my portion of the talk, I focused on the questions and challenges that might face someone attempting to start up an Open Source presence for their company.

Grass Roots?

The first thing you're faced with deciding is if you should start from the bottom up or the top down. Ultimately, you'll want the executive support from the top, but when you're just getting started you can function without it. Instead, find a good first project to be the poster child. Use this to build excitement and draw attention. Within your engineering team, it's very likely that most folks will be interested in Open Source and want to be involved. It's also just as likely that they'll have no idea how to do that. The poster child will serve as an example of not only how to do it, but that it is possible.

Start working on how to fit thinking about Open Source into the Software Development Life Cycle, for both outgoing open source and incoming open source software.

Find someone who will champion OSS for you, be that person, or share the role.

Good Intentions

The percentage of folks who tell you they are interested in sharing their software is far greater than the percentage of folks who will put in the time to share it. Realizing this upfront will save you a lot of disappointment and undelivered work.

Figure out how to embed OSS into the DNA of your new projects. Learn the build systems that your developers use and make it easy for them to fork small, cohesive modules into open source ready projects that can be composed back into their larger, internal work. For example, break out small python libraries into pypi projects.

Straight Outta Compton

Open sourcing a software project successfully as a company is more than just creating amazing code.  There no trivial amount of red tape to traverse from legal, to security, to IP. And after that there is promotion. Imagine if Eazy E had never met Jerry Heller. There might never have been an NWA as we know it or modern day rap. The role of the Open Source Office is to be the guide through all the red tape and promotional process to your developers that Jerry Heller was to NWA.

Who Cares?

Success with OSS is a living thing and it needs to be tended to. It won't be on the roadmap for most teams and it won’t be a behavior for which time is allotted. In other words: it's unlikely that most developers will be gratuitously spending their time on OSS.

The role of the OSS office is to continually drive engagement within the company. Regularly promote successes in the community or within the company. Maybe you just got a great new hire because of an OSS project or maybe one of your engineers was just recognized in the tech news. Maybe a talented employee previously on the verge of leaving renewed their commitment to the company because of engagement with OSS. Share these successes with the whole engineering team or within the leadership group.

Make the time to meet with team managers to see what projects are coming up in their backlogs. Brainstorm how OSS could be a part of that.


Finally, it's critical to keep your community happy. Never release a project without thinking about promotion and adoption, easy install, good README, etc. Keep an eye on the metrics on your projects. Celebrate healthy projects. Respond to GitHub Issues in a timely manner. Encourage pull requests! Coach your developers to be polite, be thoughtful, and to engage with the community. Create mailing lists. Consider adopting a code of conduct. Be a responsible member of the OSS community and remember that as an enterprise / company, you are setting an example and representing more than simply your company.

Final Note

These were the five points that I found most prominent from my time running Open Source at Box. However, the list of other reflections is much longer. Please see the presentation for some of the other takeaways from other members of the TODO Group. The role of Open Source Office is very critical to any company interested in being part of the OSS community, whether as a consumer or producer.

Saturday, April 2, 2016

Building Successful Teams (it's not just your manager's job)

Over the past year and a half I've been managing a small team of software developers. This past week I was reflecting on some of the practices we've developed as a team that I feel have contributed to our success as both a team and as individuals. Notwithstanding the likelihood that these are not new ideas, I wanted to collect my own reflections in a single, memorable-to-me place.

Success of the team is not measured only by the projects we have completed, but also by the steps each of the team members has made in their careers, personally and professionally. I feel that the practices outlined below are designed to achieve both of these aspects of success.

Our Practices

A rough overview of our formula is below. I've tried to keep the descriptions concise, but several of these points do merit their own blog posts.

Sidenote On Applicability

These practices evolved in a team of 3 people in an org of > 100 people in a department of > 300 people in a company of > 1000. There's a completely fair chance that some of these practices won't make sense in small companies (i.e. less than Dunbar's number) or very young companies.

Recurring Events

  • Weekly 1:1's with manager. Time for the manager to listen and the IC to talk. Check in on short term career development goals. Check in on impediments. Check in on any drama with other employees. See some more ideas, Good Tips for Your 1 on 1.
  • 6-weekly 1:1 offsite lunch to discuss career fit and plan. A deeper dive into long term career goals. A time to build rapport. Again, the IC should do most of the talking; though this is also a chance for the manager to provide guidance and reflections from their own experiences.
  • 4-weekly team offsite lunch. A chance to get out of the office and just be regular people. The fresh air and less familiar surroundings will be good for your psychology.
  • 4-weekly team lunch onsite. On the in between weeks from the offsite lunch. This just makes sure you are getting together and seeing each others faces.
  • 6-weekly team scrum retrospective. It is amazing what you learn about your team when you do this, both good things and bad things. The regular cadence also helps with accountability.
  • Weekly status emails for celebration, retrospection, and future (i.e. next week). At the least, these go to the team. I like to include my boss and other parties who helped play a part in recent success or have some stake (approvers, consulted, informed, etc.) in ongoing work. This is adopted from the PPP Concept.


These tie a team together and provide them the necessary context to self-navigate.
  • Team vision & purpose and company fit
  • Clear short term priorities. This is generally something visible like a Scrum or Kanban board. This is good for the team itself to use, but also for anyone else interested in what your team is doing.
  • Clear long term goals. These should fit with team vision and purpose. Typically, these will be the overarching epics comprising the short term priorities.
  • Rubric for roles on the team. At its worst, absence of clearly defined expectations for each role and level, can lead to feelings of unfairness or favoritism.  At its best, it provides career goals for team members and acts as a guide for what is and (as importantly) is not expected of them. 


  • Constant feedback, both good & bad. This builds respect in both directions. This also helps ensure transparency.
  • Fairness. Managers should be transparent about decisions made regarding other employees. If you feel you are being preferentially treated, speak up. If you notice it, your teammates probably do and doubtless will not appreciate it.
  • Outward communication to other teams about what you've accomplished. This is a step beyond the weekly status email. These happen anytime a major goal is achieved or an epic is completed. There is so much going on in most companies, that achievements get lost in the noise and too often only failures get any attention. If a manager isn't shouting from the rooftops about the team's success, then it's unlikely that anyone else will be.
  • Information pass downs from the manager's manager. Lots of decisions get made on high and awareness of that information about those can help your team be more successful.
  • Commitment to finish your short term priorities. New needs will come up that may be more important and vie for the team's attention & time. It's critical that you remain committed to complete your short term priorities, without this you lose trust and faith in the team. Furthermore, knowing you'll complete your commitments makes you more thoughtful about what you'll commit to.
  • You are held accountable. Whether you're a manager or an IC, if you're not held accountable then your work will suffer.

Outside the Team

  • You should ask a manager for help finding a mentor.
  • You should identify someone in upper leadership who shares your view points and is driven by the same things as you. There will be situations when you need a second opinion or someone to back you.
  • Try to cultivate a sponsor.

Parting Thoughts

Never sacrifice these things. Skipping one or two of them once or twice might be OK, but it will add up and accumulate into discontent and dissatisfaction and poor performance. You must keep yourselves accountable and hold those around you accountable.

Those lucky ones of us will find a manager who will naturally do these things, but for the rest of us we can't simply claim misfortune or "being a victim" as excuse and then give up. When it's your career on the line, it doesn't matter whose fault it is; what matters is the results you are going to get.

Additional Learning