Roy's musings

From engineer to manager

2022-08-01T14:35:00.006-07:00

In 2015, I co-founded a company with my friend. Until then I had been working as an individual contributor. Though I had been a technical lead to many projects, I hadn’t managed teams. Over the past 7+ years I have learned a great deal on project and people management. My experience has taught me the most than the books and articles I have read. In this series, I would like to summarize what has worked for me with the hope that it would be helpful for someone following similar trajectory. If you have any feedback, please leave in comments.

Project and people management

As a manager, you are managing two things: projects and people. They both require different sets of skills.

For the most part, managing projects can be learnt from reading books. But managing people is a different skill and it cannot be learnt from books alone. It requires a lot of interacting with people. It requires listening and understanding people’s needs so that you can help them succeed. Usually these needs are driven by an instinct of self preservation. If you choose to ignore these needs, you are doomed to fail as a manager and you will end up with an unproductive and unhappy team.

Project management

Task is the basic unit of project management. Though it may sound trivial, I didn't have this clarity at the start.

Tasks have priorities. Most of my spectacular failures have been around misplaced priorities. There may be a task to build a cool feature using the latest and greatest GraphQL database with micro services. There may be another task which is a boring bug fix that is blocking a customer. Your developer may be excited and start working on the cool task, while there is a waiting or disgruntled customer. It is my responsibility to prioritize the task and to help the team see why a task is important.

When I am going through the list of tasks, I ask only one question: have I assigned the right priority to the task? I follow a guideline that the tasks that are blocking a customer from getting something done demand immediate attention. Those are the ones assigned highest priority.

Depending on the priority, tasks are committed. Every committed task has deadline.

How specific the deadline should be? You can say a task will be done by 3:30 PM tomorrow. In my experience, this is usually a bad idea. I follow this rule of thumb: if the task will take less than a week of effort, I specify the deadline in days. Else I specify the deadline in weeks. For instance a task that will take three weeks, don’t specify the dead line as Wednesday 4:00 PM of the third week. I say the deadline is third week. It could happen any time during the third week. Why is this important? I have observed that teams generally have high morale when they commit to a deadline and hit it.

Tasks also have dependencies. To keep track of dependencies, every project management system provides some means. For instance, JIRA has “Blocked By” field where you can specify dependent tasks.

Illusion of infinite time

A critical mistake that I kept repeating was saying yes to every task and allowing tasks to be re-prioritized arbitrarily. At the end of the week, I will find myself very frustrated and most of what was planned at the beginning of the week was pushed to the next week. This frustration was contagious. My team also will feel frustrated. When I say yes to everything, I am living under the illusion of infinite time.

Once a set of tasks are committed, your team’s flow should not be disturbed unless there is a valid reason. I use the same guideline here: is there a customer blocked by some broken functionality? Then it makes sense to stop working on a committed task and unblock the customer. A customer being blocked is different from customer asking for a feature. When a customer is asking for a feature, you can negotiate when it will be delivered. Your doesn’t need to drop everything and start working on the feature.

Bottlenecks

The most valuable skill I developed was to identify people and process bottlenecks. You may not even recognize there is a bottleneck in your team that is preventing from scaling. I developed a simple test for identifying people bottlenecks.

Every time when someone says only X can do a task, X is a bottleneck.

The test is simple and effective. Let me explain. As a manger in a planning meeting, if you find yourself repeating statements like “DNS change can only be done by Joe”, or “bootstrapping a new server can only be done by Kathy”, you know that Joe and Kathy are bottlenecks. Over a period of time, you will find that they will accumulate a set of tasks that can only be done by them. Soon they will be overloaded and worst case burnt out.

There a few techniques you can use to address people bottlenecks. If you have to do a task twice, automate right from first time. I have seen people giving an excuse that they will automate next time as they are under time pressure. Guess what, next time to automate never comes. And you will find the person doing the same task manually next time as well. If you are under time pressure, let the person do it manually and then automate. If you don’t have time pressure, automate first.

If the task cannot be automated, due to whatever be the limitation, convert the task into a easy to follow set of steps with an associated check list. Documenting the steps will also bring to light what is involved in the task and ask yourself the question why it cannot be automated. Documenting the steps also lets someone else in the team to pick up the task the next time.

Process bottlenecks can be identified only when you have listed down steps involved in a process.

Art of asking questions

The best way to encourage your team to participate in a conversation is to ask open questions. If you ask “Isn’t Redis the right back end for this task?”, your developer might say “yes” and go and go and use it.

Instead if you ask them an open question like “What do you think is the right back end for this task?”, you will hear a totally different answer. They may tell you about a few back ends they have used in the past, what are the pros/cons of each of them, what they read in the Hacker News about this latest back end, etc. You can let your team member be a hero who came up with the right back end. When people feel that they came up with an idea, they have a strong sense of ownership and feel more accountable. If you see any issues with the solution being proposed, you can ask a follow up question that will guide them to come up with the right solution.

Who knows they may propose Redis itself. Except this time they will feel like a hero for coming up with that answer and feel totally committed to it.

Summary

I can summarize my learning as:

Being a manager involves project and people management.
Don’t fall victim to illusion of infinite time. Learn to say no.
Learn to prioritize. Every task is created with a priority.
To scale, identify and fix people and process bottlenecks.
Ask open ended questions.

Service health checks - the right way to build them

2019-12-03T23:14:00.000-08:00

Service health checks are ubiquitous. If you have built any software that relies upon any upstream service, I am sure you would have used some form of health check. Your software could be a stand alone program or it could be a proxy. You may also have built and exposed a service that is used as an upstream service by another software.

The worst way to perform health check is to pull a resource (like GET /hc.html, if your service is exposed as a HTTP service) or perform a TCP connect check in the same port where data is served. These are checks I call as in-band health checks. Please don't do these.

Based on my experience, the best way to expose health checks is by using an out-of-band mechanism. This means that you expose another port for performing health check. The client can perform a HTTP check or TCP check in the health check port. As a convenience, if you expose health check as HTTP service in health check port, you can consolidate multiple health checks like: GET /healthcheck/port1, GET /healthcheck/port2, etc.

One convention that could be used is to use a fixed offset port as control port for any data port. For instance, 80's control port is 81 and 443's control port is 444. Or 80's control port is 8080, and 443's control port is 8443. So when you need to decide if the service is up/down, you can check the control port.

Now let me explain what is the benefit of the out-of-band health checks. If you would like to take the service down gracefully for maintenance, all that you have to do is to fail health checks for that port (GET /healthcheck/port1 returns a 4xx) or stop listening in the health check port. This will not impact any of the on-going requests. You can gracefully close the connections after serving the requests or after a period of idle time. This will enable you to perform scheduled maintenance like a champ without impacting any client traffic at all. Having zero impact to any client traffic should be your number one goal, when performing scheduled maintenance.

TIL: Keeping parent directory structure while copying

2018-02-26T20:38:00.000-08:00

There had been instances when I wanted to copy "/home/roy" to a target directory "/target" as "/target/home/roy". I used to do some scripting foo to get this done. A few days back, I learned this cool option called "--parents" in cp command that will preserve the parent directory structure while copying. Made my life a lot easier on one of my backup tasks.

Today I Learned (TIL)

2017-07-24T14:45:00.002-07:00

Today I Learned (TIL) is a series of posts that contain bit sized information that I learned and found to be worthy of sharing with others and keep as a note to myself.

For the last couple of years, I had been devoting most of my time in building the start-up, Zycada Networks, that I co-founded. It makes me happy to share my knowledge. So I would like to get back to the habit of writing blog posts regularly on interesting stories, tips-and-tricks, new ideas, technology trends, etc. TIL is one part of doing it.

TIL: Sort human friendly values

2017-07-24T14:00:00.001-07:00

Sorting numeric values in the input is easy. It just takes "sort -n". But what if the input contains human friendly units. For intance, "5G", "3M", "4K", etc. There is a flag to recognize and sort based on the human friendly units: "-h".

Incorrect: du -h | sort -nr
Correct: du -h | sort -rh

Caveat: "sort -h" works only on upper-case units. "K" will be treated as kilos, but "k" will not be!

Aligning text in emacs

2017-07-19T01:06:00.000-07:00

Aligning text like a table is often a useful task. I use this workflow to make the text tidier. For instance when I have two columns of text of varying width, aligning them makes it easier to read.

Steps:
1) Select the region you would like to align (C-x h will select the entire buffer)
2) C-u M-x align

Thats it. The selected region would have been aligned based on the first line of the region.

Example:
Before:
what? who?
hello world

After:
what? who?
hello world

By default only the space is used as a delimiter. If you would like to perform a little sophisticated alignment, you can make use of the align-regex function.
city, population
new york, 8.49M
san francisco, 0.85M

Bit twiddling in JDK to generate random number

2015-03-11T02:58:00.000-07:00

Some time back a friend asked me an algorithm question:

Given an integer random number generator randomN() that can generate random number in the range [0, N), how will you generate random numbers in the range [0, M) where M

I used modulo arithmetic to generate the desired random numbers in the range [0, M). And I reasoned out that if N = q*M + r, every number in the range [0, r] has an occurrence probability of (q+1)/N, but the numbers in the range [r+1, M) has an occurrence probability of only q/N.

It is easy to visualize this. See the diagram below:

You can see that we can divide line of length N units (given in green) by lines of length M units (given in black). When N is not exactly divisible by M, in the last part alone we have only r units.

So if we choose a random integer in the line represented in green, and then take a modulo M on the value, all the values except the values in the range [r+1, M) (represented in red) will occur q+1 times. But the values in that interval will occur only q times.

So how do we generate uniform random numbers? Solution is very simple: when the generated random number is in the last segment, just discard the number and regenerate another random number. My solution looked like this:

maxAllowed = N - (N mod M)
do {
randValue = randomN()
} while (randValue >= maxAllowed)
return maxAllowed mod M

Recently I was reading the Java API documentation for Random.nextInt(M). And I stumbled upon a clever trick that actually does what I did using some bit twiddling. The next(numBits) in Java code generates random numbers of length numBits. Since signed integers are 31 bits, internally nextInt(M) calls next(31). This will return values in the range of [0, MAX_INT + 1). Now using this the code generates a random number in the range of [0, M). What is the clever trick here? Look at how integer overflow is used to detect boundary condition.

do {
bits = next(31);
val = bits % n;
} while (bits - val + (n-1) < 0);

This boundary condition is similar to "randValue >= maxAllowed" condition in my code.

Personally I feel that my code is easier to understand and (I guess) performs better. The reason why I guess my code performs better is due to the fact that it does modulo arithmetic exactly two times. But JDK's code performs modulo arithmetic every time in the loop. Also for checking the condition it performs addition of four values, while my boundary condition is a straight forward comparison.

Yet it was interesting to see this piece of code and spend some time to understand what it is actually doing.

Is accepting Optional as argument a code smell?

2014-09-08T11:20:00.000-07:00

I was reviewing some piece of code and came across a function that was taking Optional as argument. In the same class, another function was taking a couple of Optional as arguments.

When I thought about it, I felt that taking an Optional should be avoided. You can return an Optional from a function, but avoid taking Optional arguments. Before calling a function, you should check for the presence or absence of the values that you are passing. Hence a function taking one or more Optional is a code smell.

One argument that can possibly presented in favor of taking Optional as argument is every caller checking for the presence of the arguments. Consider the code example below:

If you pay attention, the error handling from the caller's point of view is ugly if the caller wants to report correct error. Much worse, the error check is done after using the values.

A side effect of product() taking Optional is that it must return an Optional. Otherwise it has to throw an exception. They both can be avoided if it doesn't take the Optional argument.

A simplified version will be:

A minor annoyance with two argument logging in SLF4J and Scala

2014-07-29T16:40:00.002-07:00

I am using Scala for one of my recent projects. For logging, I am using SLF4J/LOGback. There is one minor annoyance while you are trying to log two argument messages like:

logger.info("Some log with arg1 [{}] and arg2 [{}].", arg1, arg2)

While you compile with sbt you will get the following error:

[error] both method info in trait Logger of type (x$1: String, x$2: <repeated...>[Object])Unit

[error] and method info in trait Logger of type (x$1: String, x$2: Any, x$3: Any)Unit

[error] match argument types (String,String,String)

If you are getting this error, a small trick that I did to avoid casting to AnyRef or Object was to just add a null argument at the end which will force the Scala compiler to make use of the vararg version. LOGBack just ignores extraneous arguments. Like this:

logger.info("Some log with arg1 [{}] and arg2 [{}].", arg1, arg2, null)

Disclaimer: I am a Scala rookie, hence take my advice with a pinch of salt!

The most important keyboard shortcut you should know in IntelliJ IDEA

2014-07-21T23:59:00.001-07:00

TLDR; If you are new to IntelliJ (like me), use "Cmd+Shift+A" to find your way around.

Recently I started developing an application in Scala. I am an avid Eclipse user, but unfortunately I felt that the support for Scala is a bit clunky as of today. It was driving me nuts to see some of the Java classes highlighted in red as unknown classes, but restarting the Eclipse or refreshing project was removing those errors.

Based on my research, I felt that IntelliJ IDEA has better support for Scala. So I wanted to give it a spin. So far I feel so good that I decided to give it a try.

I prefer to get things done using keyboard shortcuts, touching the mouse only for absolutely essential needs. The most important keyboard (and in my opinion the most awesome) shortcut that you should know in IntelliJ is "Cmd+Shift+A". This will show you an input box where you can enter a partial string and you will be presented with the list of action or options that is relevant to the search term. For e.g. you can enter "override" and presented with actions relevant to "overriding".

For Emacs users, this is very similar to "apropos" command. For Eclipse users, this is similar to "Cmd+Shift+L", but only better.

An absolute essential thing you should know about Hibernate cache

2014-05-24T20:03:00.000-07:00

You might have used Hibernate for your ORM needs. The most important thing that you should about Hibernate cache is that it is implemented using a Map and a reference every entity that you have read from the database is kept in that Map. The key of that Map is the Entity ID (which could be just a Long or some form of composite primary key you have defined and wrapped in an EntityKey). The value stored is the entity itself (proxied).

If you read a 1000 entities (or rows) from the database, a reference to each one of them will be kept in the Map. If those entities have relationships specified (one-to-many or many-to-many) with other entities and those entities should be loaded eagerly, you are asking Hibernate to load a lot more than 1000 entities.

If you venture into processing a large set of rows (say 100,000 rows), a reference to every one those rows is going to be kept in the Map. Sometimes the amount of memory needed could be so large that your process might run out of memory (as mine did).

So what is the life cycle of this Map? This map is part of the "persistence context" that is referenced in Hibernate session. Hence when a Hibernate session is created, this Map contains no elements. As you keep reading or inserting entities, this Map accumulates references to these entities. When you close the session the Map is cleared.

If you would like to deal with a large volume of entities, given below is a strategy that you can follow:

Divide the entire set of entities into smaller batches (like 1000 entities per batch).
If you have made any updates, flush the session once in every batch.
Clear the session once in every batch. This should take care of evicting all the references to the entities and those entities will be GCed.

The disadvantage of this method is that if there is one or more entities that are referred across that batches, they will be read again once per batch. But the main advantage is that you will keep your memory utilization low.

Heartbleed bug in OpenSSL

2014-04-08T16:05:00.001-07:00

There was a serious vulnerability reported in the OpenSSL library that can let the attacker to dump memory contents from the server. Thus the attacker can perform offline analysis of the memory contents and identify sensitive information like private key of the server, key material for SSL sessions, decrypted data that is in memory, etc. This affects any server that uses OpenSSL to implement HTTPS.

I thought I will share some material in one place that will be helpful for people to understand the problem better.

Description of the problem can be found here.
A simple Python script to test your servers can be found here or you can use this site.
NVD entry for this issue can be found here.
How some of the companies are responding: Heroku, AWS, Lastpass.

Hope that helps.

Two important traits of building reliable distributed systems

2014-04-05T12:13:00.002-07:00

Designing a distributed system is hard enough. Even harder to design a distributed system that is reliable. There are many best practices that you can follow to make a reliable distributed system. Based on an issue that I recently troublehooted, there are a couple of them that I think are critical:

Enabling TCP keep-alive between the processes if you are using TCP
Performing all IO operations with a time out

My advise is based on my experience in Linux. But I think it should be applicable to other operating systems as well. When a host goes down with a kernel panic, none of the established connections are closed by sending a FIN or RESET packet. This cauases trouble that the peer process doesn't know about the other end of the communication being gone. When you enable TCP keep-alive, the kernel sends a zero length packet as per the configuration. Hence if the peer has died due to kernel panic, the zero length packet will not be ACKed. Thus, the peer death is detected. If the peer has died and rebooted, when the zero length packet is sent, the peer responds with RESET packet. Thus the best way to detect peer death is enabling keep-alive.

For Linux, to enable keep-alive, please refer to this page. The most important thing is after you open the socket, you should use setsockopt() to set the SO_KEEPALIVE option.

Using timeouts is one way to detect that the service quality is degrading. For e.g. when you try to fetch data from an external system, the external system might be choking due to too many requests and may not be as responsive as it should be. But if you build retry mechanisms based on timeouts, you have to be extra careful. Because sending more requests to an external system might make the situation worse than it should be.

A brief tutorial on using Guava's Optional with Jackson JSON library

2013-09-16T17:36:00.001-07:00

One serious limitation of using Jackson to deserialize the custom defined bean classe is that you cannot differentiate between a value missing in the input JSON or it is present but having null value. Consider the exampel below:

class MyBean {
  private String firstName;
  private String lastName;
  // Getters and setters here.
}

You cannot differentiate between the JSON inputs {"firstName": "John"} and {"firstName": "John", "lastName": null}. I.e. the lastName property being present in the input or not.

Guava library has an excellent tool to express missing values versus null values: Optional. Jackson supports integration with Guava library. The integration library can be accessed from jackson-datatype-guava package. To clearly express the null versus absent values, we can rewrite the bean class above as follows:

class MyBean {
  private Optional<String> firstName;
  private Optional<String> lastName;
  // Getters and setters here.
}

So before accessing the value, you will be just checking for its presence. I.e. myBean.getFirstName().isPresent().

If you don't care if the value is present or not, but just want to retrieve the value as null if absent, you can do myBean.fetFirstName().orNull().

BTW, if you are not making use of Guava libraries in your project, you are truly missing something great and makes you productive. Please give it a try.

A Python script to execute Python code like "perl -ne"

2013-07-15T14:06:00.002-07:00

I wrote a small utility script that can be used to run a small snippet of Python code like "perl -ne". I find it very useful for my needs. Hope it helps you too. Any suggestions welcome.
You can find the script as a gist here.

Setting the terminal window title - version 2

2013-07-15T13:26:00.000-07:00

I had earlier written a small snippet about setting the window title from command line. Based on my experience, I felt that I could make it a lot simpler. Here is version of the same function.

function wtitle {
if [ -z "$ORIG_PS1" ] ; then
ORIG_PS1=$PS1
fi
export PS1="\[\033]0;$1 - \u@\h:\w\007\]$ORIG_PS1"
}

A rarely used but very useful option in grep

2013-07-03T11:56:00.001-07:00

I usually do a lot of log analysis. I search for patterns in multiple files in multiple hosts. Then I collate the result and do processing on the result lines. A sample output looks like:

/tmp/input1.txt: line containing pattern

/tmp/input2.txt: another line containing pattern

As it turns out, I don't need the file names in the grep result. I always used to remove the file name prefixes using a Perl one-liner. Silly me!

I was pretty sure that this was a common problem and it must have been solved already. When I referred to the man page of grep, I came across this gem: -h. If you specify this option, grep will not prefix each line with a the file name.

There is also -H option which will prefix each line with a filename even if you are searching in only one file.

Returning to Python

2013-06-03T14:02:00.000-07:00

After a couple of years or so, I starting making use Python as my main programming language for one of the projects. This time I was making use of the virtualenv to install Python with various modules and just tar it up and copy to different machines. virtualenv saved me tons of time.

Zig-zag search

2013-04-23T18:37:00.000-07:00

This is an interesting problem that I ran into. The problem definition goes like this.

You are given an array of integers. The array is considerably large (say 5 million elements). You are given two inputs: an index i in the array and an integer value v. Start searching the array for value v from the index i, and expand your search towards the two edges of the array. Return the index where the value v occurs closest to index i. If the value v occurs on both sides of index i at an equal distance, return the lower of the two indices. If the value v does not occur at all, return -1.

It was very interesting to solve this problem. Give it a shot, you might also like it.

Installing Emacs 24.3.1

2013-03-23T22:53:00.001-07:00

Earlier I blogged about a little hurdle that I ran into when I was trying to install Emacs 24.1. Since Emacs 24.3.1 was released recently, I thought I would give it a spin.

After downloading the source code, I unzipped the source code and ran configure command. I got a similar error that I was getting before.

 checking for libXaw... configure: error: No X toolkit could be found.  
 If you are sure you want Emacs compiled without an X toolkit, pass  
  --with-x-toolkit=no  
 to configure. Otherwise, install the development libraries for the toolkit  
 that you want to use (e.g. Gtk+) and re-run configure.

I am trying to install Emacs on Mint 14. So to satisfy all the dependencies, I installed the missing packages.

  sudo apt-get update   
  sudo apt-get install libgtk2.0-dev libtiff4-dev libgif-dev libpng12-dev libxpm-dev libncurses-dev libjpeg-dev libjpeg8-dev libjpeg-turbo8-dev

After installing the dependencies, the usual three step process worked fine.

 ./configure  
 ./make  
 sudo make install

Hope this helps if you run into the same problem.

A late realization on embedding the code using gist

2013-03-20T14:54:00.000-07:00

Off late I started using gist to embed source code in my blog entries. I was thinking about the consequences of doing this (or any form of embedding text using an external site). I realized the following:

First and foremost the search engines don't get to index the page based on the key words in the embedded source code. For e.g. consider an embedded gist that demonstrates ServerSocket. Unless I mention about ServerSocket in my blog somewhere, the serarch engine will not associate the blog entry with the ServerSocket as that word appears only in the embedded source code.
When peopele search for a specific key word in the embedded source code, they will be taken directly to the gist page, instead of the blog entry. This is bad because the user will not get the context and explanation around the source code.

To understand the depth of the problem, please search for alias-to-jumphosts-alist in Google. You will find that the gist is shown first and then the blog entry. Even in this case the blog entry is shown only because it mentions the function in it.

In future I should try to embed the source code in the blog itself and make use of a source code formatter like SyntaxHighligher.

Using dirtrack-mode inside shell mode

2013-03-14T13:25:00.000-07:00

I usually try to automate the things that I repeatedly perform. One the things that I recently automated was:

Create a directory with a prefix and today's date or time as suffix.
Chdir to the most recently created directory.

The source code for these utility functions is given below:

When I use these utility functions inside the Emacs' shell-mode, the shell-mode was unable to keep track of the current directory. The issue is that I am changing directories without making use of the cd command.

Then came the dirtrack-mode for the rescue. The idea is very simple: you specify the regular expression where the path appears in your shell prompt. The dirtrack-mode figures out the rest of the stuff.

Now my .emacs file contains the following two lines:

Thats it. Works like a charm. Please note that you might have to modify the regular expression to match where the full path appears in your prompt.

One sequence per table or one sequence per database

2013-02-11T15:57:00.001-08:00

Let us assume that you are implementing RESTful APIs for your service. Your service has the following two models: users and tweets. While inserting new entities, you should genertate IDs. The IDs for each of these models can be generated in two ways:

You can use a sequence (if you are using Oracle) or autoincrement feature (if you are using MySQL) to have per model IDs.
You can use a global sequence for all the models.

If you are following the first strategy, you will have user IDs 1, 2, 3, 4, etc. and tweet IDs 1, 2, 3, 4, etc. If you are following the second strategy, you will have user IDs 1, 3, 4, 8, etc. and the tweet IDs 2, 5, 6, 7, etc.

Thinking about it, I felt that using the first strategy will leak information. Consider some one doing a tweet every day at 10:00 AM and get the tweet ID. If first day the tweet ID is 100, and the second day the tweet ID is 200, etc. That person can infer that your system is receiving 100 tweets/day. I don't know how sensitive this information can be.

I would appreciate your thoughts. Please share them in comments.

The issue with Emacs "cd" function and CDPATH

2013-02-02T19:06:00.001-08:00

Recently I wasted sometime trying to figure out an issue with "cd" function and autocompletion in Emacs, while I had a value set for CDPATH environment variable. I hope it saves some time for someone who might bump into the same issue.

I had CDPATH environment variable set and it didn't have "." (current directory) as one of the components. When I tried autocompletion while running "cd" function, it didn't show any of the subdirectories under the current directory. The directories it showed for completion were from somewhere else. As soon as I added ".", I was able to see all the subdirectories of current directory in the autocompletion list.

Hope this saves some time for you as well.

Enabling multiple cores in VirtualBox

2013-01-23T15:53:00.001-08:00

This post is a follow up to my earlier post Moving from VMWare Player to VirtualBox.

Once you have set up your VirtualBox instance, the first challenge you will face is that the guest OS may possibly be very slow due to the fact that the number of cores allowed is only one. Hence you will have to increase the number of cores that your guest OS can make use of. Open the VirtualBox manager, click on your VM, then click on the Settings button. In the Settings window, click on the System on the left pane and select the Processor tab on the right.

In this page, you can increase the number of processors. If you haven't already enabled the virtualization in your processor, you are likely to get an error when you click on OK. The error message will look like this:

Failed to open a session for the virtual machine Lubuntu.
VD: error VERR_NOT_SUPPORTED opening image file 'C:\VMs\Lubuntu.vmdk' (VERR_NOT_SUPPORTED).
Result Code: E_FAIL (0x80004005)Component: ConsoleInterface: IConsole {db7ab4ca-2a3f-4183-9243-c1208da92392}

If you see this error, you haven't possibly enabled the virtualization in the processor. Virtualization can be enabled only from the BIOS. Please refer to your computer's manufacturer web site to find out how to enable this. For your reference, I am giving a link to how to enable it in ThinkPad W520 (which I own).

Once the virtualization is enabled, you can restart your computer and try to increase the number of cores dedicated your guest OS again. Hopefully, you will not get the same error again.

Thats it. Boot your guest OS and enjoy!