Category Archives: Bash

CLI hotkey and navigation guide

I have been meaning to write this post for quite a while now but have always managed to forget.  I have been piecing together useful terminal shortcuts, commands and productivity tools since I started using Linux back in the day.  If you spend any amount of time in the terminal you should hopefully know about some of these tricks already but more importantly, if you’re like me, are always looking for ways to improve the efficiency of your bash workflow and making your life easier.

There are a few things that I would quickly like to note.  If you use tmux as your CLI session manager you may not be able to use some of the mentioned hotkeys to get around by default if you don’t have some settings turned on in your configuration file.

You can take a look at my custom .tmux.conf file if you’re interested in screen style bindings plus configuration for hotkeys.  If you simply want to add the option that turns on the correct hotkey bindings for your terminal, add this line to your ~/.tmux.conf file

set-window-option -g xterm-keys on

Also, if you are a Mac user, and don’t already know about it, I highly recommend checking out iTerm2.  Coming primarily from a Linux background the hotkey bindings in Mac OS X are a little bit different than what I am used to and were initially a challenge for me to get accustomed to.  The transition for me took a little bit but iTerm has definitely helped me out immensely, as well as a few other ticks learned along the way.  I really haven’t dug through all the options in iTerm but there are a huge number of options and customizations that can made.

The only thing I have been interested in so far is the navigation which I will highlight below.

Adjust iTerm keybindings – As I mentioned, I am used to using Linux keybinding so a natural fit for my purposes is the option key.  The first step is to disable the custom binding in the iTerm preferences.  To do this, click iTerm -> Preferences -> Profiles -> Keys and find the binding for option left arrow and option right arrow and remove them from the default profile.

Next, add the following to your global key bindings, iTerm -> Preferences -> Keys.

iterm2

 

 

 

Move left one word

  • Keyboard shortcut: ??
  • Action: Send Escape Sequence
  • Escape: b

Move right one word

  • Keyboard shortcut: ??
  • Action: Send Escape Sequence
  • Escape: f

Finally, it is also worth pointing out that I use zsh for my default shell.  There are some really nice additions that zsh offers over vanilla bash.  I recently ran across this blog post which has some awesome tips.  I have also written about switching to zsh here.  Anyway, here is the lis.  It will grow as I find more tips.

Basic navigation:

  • Ctrl-left/right arrow – Jump between words quickly.
  • Opt-left/right arrow – Custom iTerm binding for jumping between words quickly.
  • Alt-left/right arrow – Linux only.  Jump between words quickly.
  • Esc-b/f – Mac OS.  Similar to arrow keys, move between words quickly.
  • Alt-b – Linux only.  Jump back one word.  Handy with other hotkeys overridden.
  • Ctrl-a – Jump to the beginning of a line (doesn’t work with tmux mappings).
  • Ctrl-e – Jump to the end of a line.
  • End – SImilar to ctrl-e this will send your cursor to the end of the line.
  • Home – Similar to End, except jumps to the beginning of the line.

Intermediate navigation:

  • Ctrl-u – Copy entire command to clipboard.
  • Ctrl-y – Paste previously copied ctrl-u command in to the terminal.
  • Ctrl-w – Cut a word to the left of the cursor.
  • Alt-d – Cut after word after the cursor position

Advanced use:

  • Ctrl-x Ctrl-e – Zsh command.  Edit the current command in your $EDITOR, which for me is vim
  • Ctrl-r – Everybody hopefully should know this one.  It is basically recursive search history
  • Ctrl-k – Erase everything after the current cursor position.  Handy for long commands
  • !<command>:p – Print the last command
  • cd … – Zsh command.  This can be easily aliased but will jump up two directories
  • !$ – Quickly access the last argument of the last command.

Zsh tab completion

Tab completion with Zsh is awesome, it’s like bash completion on steroids.  I will attempt to highlight some of my favorite tab completion tricks with Zsh.

Directory shorthand – Say you need to get to a directory that is nested deeply.  You can use the first few characters that will uniquely match to that directory to navigate instead of typing out the whole command.  So for example, cd /u/lo/b will expand out to /usr/local/bin.

command specific history – This one comes in handy all the time.  If you need to grab a command that you don’t use very often you can user Ctrl-r to match the first part of the command and from there you can up arrow to locate the command you typed.

Spelling and case correction – Bash by default can get annoying if you have a long command typed out but somehow managed to typo part of the command.  In zsh this is (sometimes) corrected for you automatically when you <tab> to complete the command.  For example if you are changing dirs in to the ‘Documents’ directory you can type ‘cd ~/doc/’ and the correct location will be expanded for you.

This list will continue to grow as I find more handy shortcuts, hotkeys or generally other useful tips and tricks that I find in my day to day command line work.  I really want to build a similar list for things in Vim but my Vim skills are unfortunately lacking plus there is already some really nice documentation and guidance out there already.  If you are interested in writing up a Vim productivity post I would love to post it.  Likewise, if you have any other nice shortcuts or tips you think are worth mentioning, post them in the comments and I will try to get them added to the list.

Add environment variable file to fig

If you haven’t heard of fig and are using Docker, you need to check it out.  Basically Fig is a tool that allows users to quickly create development environments using Docker.  Fig alleviates the complexity and tediousness of having to manually bring containers up and down, stitch them together and basically orchestrate a Docker environment.  On top of this, Fig offers some other cool functionality, for example, the ability to scale up applications.  I am excited to see what happens with the project because it was recently merged in to the Docker project.  My guess is that there will be many new features and additions to either Docker if Fig gets rolled in to the Docker core project.  For now, you can check out Fig here if you haven’t heard of it and are interested in learning more.

One issue that I have run in to is that there is currently not a great way to handle a large number of environment variables in fig.  In Docker there is an option that allows a user to pass in an environment variable file with the –env file <filename> flag.  To do the same with Fig in its current form, you are forced to list out each individual environment variable in your configuration which can quickly become tedious and confusing.

There is a PR out for adding in the ability to pass an environment variable file in to fig via the env-file option in a fig.yml file.  This approach to me is much easier than adding each environmental variable separately to the configuration with the environment option as well as having to update the fig.yml configuration if any of the values ever change.  I know that functionality like this will get merged eventually but until then I have been using the PR as a workaround to solve this issue, I think that this is also a good opportunity to show people how to get a project working manually with custom changes.  Luckily the fix isn’t difficult.

This post will assume that you have git, python and pip installed.  If you don’t have these tools installed go ahead and get that done.  The first step is to clone the fig project on github on to your local machine, see above for the link to the PR.

git clone git@github.com:docker/fig.git

Jump in to the fig project you just cloned and edit the service.py file.  This is the file that handles the processing of environment variables.  There are a few sections that need to be updated in the config.  Check the PR to be sure, but at the time of the writing, the following code should be added.

Line 55

- supported_options = DOCKER_CONFIG_KEYS + ['build', 'expose']
+ supported_options = DOCKER_CONFIG_KEYS + ['build', 'expose', 'env-file']

Line 318

+ def _get_environment(self):
+ env = {}
+
+ if 'env-file' in self.options:
+ env = env_vars_from_file(self.options['env-file'])
+
+ if 'environment' in self.options:
+ if isinstance(self.options['environment'], list):
+ env.update(dict(split_env(e) for e in self.options['environment']))
+ else:
+ env.update(self.options['environment'])
+
+ return dict(resolve_env(k, v) for k, v in env.iteritems())
+

LIne 352

- if 'environment' in container_options:
- if isinstance(container_options['environment'], list):
- container_options['environment'] = dict(split_env(e) for e in container_options['environment'])
- container_options['environment'] = dict(resolve_env(k, v) for k, v in container_options['environment'].iteritems())
+ container_options['environment'] = self._get_environment()

Line 518

+
+
+def env_vars_from_file(filename):
+ """
+ Read in a line delimited file of environment variables.
+ """
+ env = {}
+ for line in open(filename, 'r'):
+ line = line.strip()
+ if line and not line.startswith('#') and '=' in line:
+ k, v = line.split('=', 1)
+ env[k] = v
+ return env

That should be it.  Now you should be able to install fig with the new changes.  Make sure you are in the root fig directory that contains the setup.py file.

sudo python setup.py develop

Now you should be able to edit your fig.yml file to reflect the changes that have been added to fig via env-file.  Here is what a sample configuration might look like.

testcontainer:
 image: username/testcontainer
 ports:
 - "8080:8080"
 links:
 - "mongodb:mongodb"
 env-file: "/home/username/test_vars"

Notice that nothing else changed.  But instead of having to list out environment variables one at a time we can simply read in a file.  I have found this to be very useful for my workflow, I hope others can either adapt this or use this as well.  I have a feeling this will get merged in to fig at some point but for now this workaround works.

Introduction to boot2docker

boot2docker

If you work on a Mac (or Windows) and use Docker then you probably have heard of boot2docker.  If you haven’t heard of it before, boot2docker is basically a super lightweight Linux VM that is designed to run Docker containers.  Unfortunately there is no support (yet) in Mac OS X or Windows kernels for running Docker natively so this lightweight VM must be used as an intermediary layer that allows the host Operating Systems to communicate with the Docker daemon running inside the VM.  This solution really is not that limiting once you get introduced to and become comfortable with boot2docker and how to work around some of the current limitations.

Because Docker itself is such a new piece of software, the ecosystem and surrounding environment is still expanding and growing rapidly.  As such, the tooling has not had a great deal of time to mature.  So with pretty much anything that’s new, especially in the software and Open Source world, there are definitely some nuances and some things to be aware of when working with boot2docker.

That being said, the boot2docker project bridges a gap and does a great job of bringing Docker to an otherwise incompatible platform as well as making it easy to use across platforms, which especially useful for furthering the adoption of Docker among Mac and Windows users.

When getting started with boot2docker, it is important to note that there are a few different things going on under the hood.

Components

The first component is VirtualBox.  If you are familiar with virtual machines, there’s pretty much nothing new here.  It is the underpinning of running the VM and is a common tool for creating and managing VM’s.  One important note here about VBox.  This is currently the key to make volume sharing work with boot2docker to allow a user to pass local directories and files in to containers using its shared folder implementation.  Unfortunately it has been pretty well documented that vboxsf (shared folders) have not great performance when compared to other solutions.  This is something that the boot2docker team is aware of and working on for future reference.  I have a workaround that I will outline below if anyone happens to hit some of these performance issues.

The next component is the VM.  This is a super light weight image based on Tiny Core Linux and the 3.16.4 Linux kernel with AUFS to leverage Docker.  Other than that there is pretty much nothing else to it.  The TCL image is about 27MB and boots up in about 5 seconds, making it very fast, which is nice to get going with quickly.  There are instructions on the boot2docker site for creating custom .iso’s if you are interested as well if you are’t interested in building your own customized TCL.

The final component is called boot2docker-cli, which is normally referred to as the management tool.  This tools does a lot of the magic to get your host talking to the VM with minimal interaction.  It is basically the glue or the duct tape that allows users to pass commands from a local shell in to the container and get Docker to do stuff.

Installation

It is pretty dead simple to get boot2docker set up and configured.  You can download everything in one shot from the links on their site http://boot2docker.io or you can install manually on OSX with brew and a few other tools.  I highly recommend the packaged installer, it is very straight forward and easy to follow and there is a good video depiction of the process on the boot2docker site.

If you choose to install everything with brew you can use the following commands as a reference.  Obviously it will be assumed that brew is already installed and set up on your OSX system.  The first step is to install boot2docker.

brew install boot2docker

You might need to install Virtualbox separately using this method, depending on whether or not you already have a good version of Virtualbox to use with boot2docker.

The following commands will assume you are starting from scratch and do not have VBox installed.

brew update
brew tap phinze/homebrew-cask
brew install brew-cask
brew cask install virtualbox

That is pretty much it for installation.

Usage

The boot2docker CLI is pretty straight forward to use.  There are a bunch of commands to help users interface with the boot2docker VM from the command line.  The most basic and simple usage to initialize and create a vanilla boot2docker VM can be done with the following command.

boot2docker init

This will pull down the correct image and get the environment set up.  Once the VM has been created (see the tricks sections for a bit of customization) you are ready to bring up the VM.

boot2docker start

This command will simply start up the boot2docker VM and run some behind the scenes  tasks to help make using the VM seamless.  Sometimes you will be asked to set ENV variables here, just go ahead and follow the instructions to add them.

There are a few other nice commands that help you interact with the boot2docker VM.  For example if you are having trouble communicating with the VM you can run the ip command to gather network information.

boot2docker ip

If the VM somehow gets shut off or you cannot access it you can check its status.

boot2docker status

Finally there is a nice help command that serves as a good guide for interacting with the VM in various ways.

boot2docker help

The commands listed in this section will for the most part cover 90% of interaction and usage of the boot2docker VM.   There is a little bit of advanced usage with the cli covered below in the tricks section.

Tricks

You can actually modify some of the default the behavior of your boot2docker VM by altering some of the underlying boot2docker configurations.  For example, boot2docker will look in $HOME/.boot2docker/profile for any custom settings you may have.  If you want to change any network settings, adjust memory or cpu or a number of settings, you would simply change the profile to reflect the updated changes.

You can also override the defaults when you create your boot2docker VM by passing some arguments in.  If you want to change the memory or disk size by default, you would run something like

boot2docker init --memory=4096 --disksize=60000

Notice the –disksize=60000.  Docker likes to take up a lot of disk space for some of its operations, so if you can afford to, I would very highly recommending that you adjust the default disk size for the VM to avoid any strange running out of disk issues.  Most Macbooks or Windows machines have plenty of extra resources and big disks so usually there isn’t a good reason to not leverage the extra horsepower for your VM.

Troubleshooting

One very useful command for gathering information about your boot2docker environment is the boot2docker config command.  This command will give you all the basic information about the running config.  This can be very valuable when you are trying to troubleshoot different types of errors.

If you are familiar with boot2docker already you might have noticed that it isn’t a perfect solution and there are some weird quirks and nuances.  For example, if you put your host machine to sleep while the boot2docker VM is still running and then attempt to run things in Docker you may get some quirky results or things just won’t work.  This is due to the time skew that occurs when you put the machine to sleep and wake it up again, you can check the github issue for details.  You can quickly check if the boot2docker VM is out of sync with this command.

date -u; boot2docker ssh date -u

If you notice that the times don’t match up then you know to update your time settings.  The best fix for now that I have found for now is to basically reset the time settings by wrapping the following commands in to a script.

#!/bin/sh
 
# Fix NTP/Time
boot2docker ssh -- sudo killall -9 ntpd
boot2docker ssh -- sudo ntpclient -s -h pool.ntp.org
boot2docker ssh -- sudo ntpd -p pool.ntp.org

For about 95% of the time skew issues you can simply run sudo ntpclient -s -h pool.ntp.org to take care of the issue.

Another interesting boot2docker oddity is that sometimes you will not be able to connect to the Docker daemon or will sometimes receive other strange errors.  Usually this indicates that the environment variables that get set by boot2docker have disappeared,  if you close your terminal window or something similar for example.  Both of the following errors indicate the issue.

dial unix /var/run/docker.sock: no such file or directory

or

Cannot connect to the Docker daemon. Is 'docker -d' running on this host?

The solution is to either add the ENV variables back in to the terminal session by hand or just as easily modify your bashrc config file to read the values in when the terminal loads up.  Here are the variables that need to be reset, or appended to your bashrc.

export DOCKER_CERT_PATH=/Users/jmreicha/.boot2docker/certs/boot2docker-vm
export DOCKER_TLS_VERIFY=1
export DOCKER_HOST=tcp://192.168.59.103:2376

Assuming your boot2docker VM has an address of 192.168.59.103 and a port of 2376 for communication.

Shared folders

This has been my biggest gripe so far with boot2docker as I’m sure it has been for others as well.  Mostly I am upset that vboxsf are horrible and in all fairness the boot2docker people have been awesome getting this far to get things working with vboxsf as of release 1.3.  Another caveat to note if you aren’t aware is that currently, if you pass volumes to docker with “-v”, the directory you share must be located within the “/Users” directory on OSX.  Obviously not a huge issue but something to be aware if you happen to have problems with volume sharing.

The main issue with vboxsf is that it does not do any sort of caching sort of caching so when you are attempting to share a large amount of small files (big git repo’s) or anything that is filesystem read heavy (grunt) performance becomes a factor.  I have been exploring different workarounds because of this limitation but have not found very many that I could convince our developers to use.  Others have had luck by creating a container that runs SMB or have been able to share a host directory in to the boot2docker vm with sshfs but I have not had great success with these options.  If anybody has these working please let me know I’d love to see how to get them working.

The best solution I have come up with so far is using vagrant with a customized version of boot2docker with NFS support enabled, which has very little “hacking” to get working which is nice.  And a good enough selling point for me is the speed increase by using NFS instead of vboxsf, it’s pretty staggering actually.

This is the project that I have been using https://vagrantcloud.com/yungsang/boxes/boot2docker.  Thanks to @yungsang for putting this project together.  Basically it uses a custom vagrant-box based off of the boot2docker iso to accomplish its folder sharing with the awesome customization that Vagrant provides.

To get this workaround to work, grab the vagrantfile from the link provided above and put that in to the location you would like to run Vagrant from.  The magic sauce in the volume sharing is in this line.

onfig.vm.synced_folder ".", "/vagrant", type: "nfs"

Which tells Vagrant to share your current directory in to the boot2docker VM in the /vagrant directory, using NFS.  I would suggest modifying the default CPU and memory as well if your machine is beefy enough.

v.cpus = 4
v.memory = 4096

After you make your adjustments, you just need to spin up the yungsang version of boot2docker and jump in to the VM.

vagrant up
vagrant ssh

From within the VM you can run your docker commands just like you normally would.  Ports get forwarded through to your local machine like magic and everybody is happy.

Autosnap AWS snapshot and volume management tool

This is my first serious attempt at a Python tool on github.  I figured it was about time, as I’ve been leveraging Open Source tools for a long time, I might as well try to give a little bit back.  Please check out the project and leave feedback by emailing, opening a github or issue or commenting here, I’d love to see what can be done with this tool, there are lots of bugs to shake out and things to improve.  Even better if you have some code you’d like to contribute, this is very much a work in progress!

Here is the project – https://github.com/jmreicha/autosnap.

Introduction

Essentially, this tool is designed to ease the management of the snapshot and volume lifecycle in an AWS environment.  I have discovered that snapshots and volumes can be used together to form a simple backup management system, so by simplifying the management of these resources, by utilizing the power of the AWS API, you can easily manage backups of your AWS data.

While this obviously isn’t a full blown backup tool, it can do a few handy things like leverage tags to create and destroy backups based on custom expiration dates and create snapshots based on a few other criteria, all managed with tags.  Another cool thing about handling backups this way is that you get amazing resiliency by storing snapshots to S3, as well as dirt cheap storage.  Obviously if you have a huge number of servers and volumes your mileage will vary, but this solution should scale up in to the hundreds, if not thousands pretty easily.  The last big bonus is that you can nice granularity for backups.

For example, if you wanted to keep a weeks worth of backups across all your servers in a region, you would simply use this tool to set an expiration tag of 7 days and voila.  You will have rolling backups, based on snapshots for the previous seven days.  You can get the backup schedule fairly granular, because the snapshots are tagged down to the hour. It would be easy to get them down to the second if that is something people would find useful, I could see DB snapshots being important enough but for now it is set to the hour.

The one drawback is that this needs to be run on a daily basis so you would need to add it to a cron job or some other tool that runs tasks periodically.  Not a drawback really as much of a side note to be aware of.

Configuration

There is a tiny bit of overhead to get started, so I will show you how to get going.  You will need to either set up a config file or let autosnap build you one.  By default, autosnap will help create one the first time you run it, so you can use this command to build it:

autosnap

If you would like to provide your own config, create a file called ‘.config‘ in the base directory of this project.  Check the README on the github page for the config variables and for any clarifications you may need.

Usage

Use the –help flag to get a feeling for some of the functions of this tool.

$ autosnap --help

usage: autosnap [--config] [--list-vols] [--manage-vols] [--unmanage-vols]
 [--list-snaps] [--create-snaps] [--remove-snaps] [--dry-run]
 [--verbose] [--version] [--help]

optional arguments:
 --config          create or modify configuration file
 --list-vols       list managed volumes
 --manage-vols     manage all volumes
 --unmanage-vols   unmanage all volumes
 --list-snaps      list managed snapshots
 --create-snaps    create a snapshot if it is managed
 --remove-snaps    remove a snapshot if it is managed
 --version         show program's version number and exit
 --help            display this help and exit

The first thing you will need to do is let autosnap manage the volumes in a region:

autosnap --manage-vols

This command will simply add some tags to help with the management of the volumes.  Next, you can take a look and see what volumes got  picked up and are now being managed by autosnap

autosnap --list-vols

To take a snapshot of all the volumes that are being managed:

autosnap --create-snaps

And you can take a look at your snapshots:

autosnap --list-snaps

Just as easily you can remove snapshots older than the specified expiration date:

autosnap --remove-snaps

There are some other useful features and flags but the above commands are pretty much the meat and potatoes of how to use this tool.

Conclusion

I know this is not going to be super useful for everybody but it is definitely a nice tool to have if you work with AWS volumes and snapshots on a semi regular basis.  As I said, this can easily be improved so I’d love to hear what kinds of things to add or change to make this a great tool.  I hope to start working on some more interesting projects and tools in the near future, so stay tuned.

Patching CVE-6271 (shellshock) with Chef

If you haven’t heard the news yet, a recently disclosed vulnerability has been released that exploits environmental variables in bash.  This has some far reaching implications because bash is so widespread and runs on many different types of devices, for example network gear, routers, switches, firewalls, etc.  If that doesn’t scare you then you probably don’t need to finish reading this article.  For more information you can check out this article that helped to break the story.

I have been seeing a lot “OMG the world is on fire, patch patch patch!” posts and sentiment surrounding this recently disclosed vulnerability, but basically have not seen anybody taking the time to explain how to patch and fix this issue.  It is not a difficult fix but it might not be obvious to the more casual user or those who do not have a sysadmin or security background.

Debian/Ubuntu:

Use the following commands to search through your installed packages for the correct package release.  You can check the Ubuntu USN for versions.

dpkg -l | grep '^ii' or
dpkg-query --show bash

If you are on Ubuntu 12.04 you will need update to the following version:

bash    4.2-2ubuntu2.3

If you are on Ubuntu 13.10, and have this package (or below), you are vulnerable.  Update to 14.04!

 bash 4.2-5ubuntu3

If you are on Ubuntu 14.04, be sure to update to the most recently patched patch.

bash 4.3-7ubuntu1.3

Luckily, the update process is pretty straight forward.

apt-get update
apt-get --only-upgrade install bash

If you have the luxury of managing your environment with some sort of automation or configuration management tool (get this in place if you don’t have it already!) then this process can be managed quite efficiently.

It is easy to check if a server that is being managed by Chef has the vulnerability by using knife search:

knife search node 'bash_shellshock_vulnerable:true'

From here you could createa a recipe to patch the servers or fix each one by hand.  Another cool trick is that you can blast out the update to Debian based servers with the following command:

knife ssh 'platform_family:debian' 'sudo apt-get update; sudo apt-get install -y bash'; knife ssh 'platform_family:redhat' 'sudo yum -y install bash'

This will iterate over every server in your Chef server environment that is in the Debain family (including Ubuntu) or RHEL family (including CentOS) and update the server packages so that the latest patched bash version gets pulled down and then gets updated to the latest version.

You may need to tweak the syntax a little, -x to override the ssh user and -i to feed an identity file.  This is so much faster than manually installing the update on all your servers or even fiddling around with a tool like Fabric, which is still better than nothing.

One caveat to note:  If you are not on an LTS version of Ubuntu, you will need to upgrade your server(s) first to an LTS, either 12.04 or 14.04 to qualify for this patch.  Ubuntu 13.10 went out of support in August which was about a month ago as per the time of this writing so you will want to get your OS up date.

One more thing:  The early patches to address this vulnerability did not entirely fix the issue, so make sure that you have the correct patch installed.  If you patched right away there is a good chance you may still be vulnerable, so simply rerun your knife ssh command to reapply the newest patch, now that the dust is beginning to settle.

Outside of this vulnerability, it is a good idea to get your OS on an Ubuntu LTS version anyway to continue receiving critical updates for software as well as security patches for a longer duration than the normal, 6 month release cycle of the server distribution.