Git workspaces explained

Working in git is complicated for new users. One of the reasons is that it is quite hard to grasp where are some actions happening.  Although some actions can be done from local to remote workspaces they are not recommended. The reason is that when we expose our code changes to other we cannot perform actions that we would do like we do it locally. All those actions will be mentioned in this article with short description and explained with greater detail in subsequent articles.

Working areas in git

1. Working directory
2. Index (Staging area)
3. Local repository
4. Remote repository

1. Working directory

The area where we edit our files.

2. Index (Staging area)

The area where are the files ready to commit to our local repository.

3. Local Repository

 The are where we put code we think we have finished editing.

4. Remote repository

If we just put our code to remote repository we might consider it as backup, or if we interact with others we have an additional step.

Local vs Remote workspace

Also we need to separate what actions we perform on our computer (locally) or with others. Remote workspace can be defined as some other repository on the same computer, network storage, remote computer or dedicated service like github, bitbucket, gitlab, .... It is

Local workspace

We can define local workspace as everything we do using our computer without any interaction with remote code. In that area we can put following workspaces: working directory, index and local repository.

The usual workflow in local workspace is following:

• Putting into local repository
  We create code and add it into the staging area, we can check the changes we are  about to put into the local repository.
• Getting out of the local repository
  We get the code from the repository into our working directory

Remote workspace 

I would define remote workspace how we have interaction with others. So it is interaction between our local repository and remote repository.

The usual workflow in remote workspace:

• Putting into remote repository
  - single-user
    Just put code into the the remote repository
  - multi-user
    Create a request to put code into the remote repository, 
    some other user needs to accept it after making a code review

• Getting code from the remote repository
  There are two steps involved: fetching and merging the code.
  First we fetch changes, see what has been changed, and merge to our local repository.

This is only introductionary post about git workspaces.

Vim plugins

There are many plugins out in the world for Vim and it takes time to investigate them and start to use them. I am slowly starting to become better and better Vim user. Some of the plugins are implemented in Vim add-ons for other code editors, or IDEs (integrated development environments).

If you are planning to use Vim plugins I highly recommend using some of Vim plugin manager. Vim 8 should contain a plugin manager, but I am using dein plugin manager. I used NeoBundle plugin manager before but it is deprecated. One of the major differences between NeoBundle and Dein that NeoBundle can be run on Windows. Since I am not using Windows anymore (although occasionally) I use Dein.

The list of Vim plugins I use:

• vim-surround 
• vim-airline
• vim-airline-themes
• vim-table-mode

A bit about those plugins.

Vim-surround (https://github.com/tpope/vim-surround)

Surround.vim is all about "surroundings": parentheses, brackets, quotes, XML tags, and more. The plugin provides mappings to easily delete, change and add such surroundings in pairs.

The documentation on its webpage sufficient and clear although I was confused a bit how to surround the selection of text. 

It is important to note that Eclipse plugin Vrapper support this plugin. 

I really love the plugin and use it very often.

Vim-airline (https://github.com/vim-airline/vim-airline)

It is just a nice status line that changes colour depending on the current Vim mode. If vim-fugitive is installed it shows which branch is active. Also, it displays various info about the file.

vim-airline-themes (https://github.com/vim-airline/vim-airline-themes)

Custom themes for the vim-airline plugin. 

vim-table-mode (https://github.com/dhruvasagar/vim-table-mode)

Quite useful if you want to make tables in the textual files. 

Excellent documentation on the github page.

Don't forget to use easy activation/deactivation for the plugin mode.

When in the normal mode type `<Leader>tm` and it will switch to the new mode.

This mode is more like a layer over the Insert mode.

<Leader> is a special key, `\` by default but it can be easily mapped to another value.

RHCSA vs LFCS

On this blog, I would like the differentiate these two certificates. I am in process of learning linux operating system and I would like to get certified. My goal is to pinpoint the pros and cons of each certificate and differences between them related to the exam objectives.


                         RHCSA                                               LFCS

Price:             460 € + VAT                                      300$
Validity:        3 years                                                2 years
Free Retake:      No                                                  1 free retake
Pre-requisites:   No                                                  No
Exam duration:  2.5 hrs                                            2 hrs
Passing score:    not defined                                     74%

There is a long list of course objective on both sides, some are more detailed in RHCSA list.

Links to the exam objectives:

• LFCS exam objectives
• RHCSA exam objectives

If we read the objectives we notice that many objectives are overlapping (maybe not positioned in the same area). 

There are many exam mocks for RHCSA and it is possible to take an assessment test on RedHat.

We can assess our knowledge using the following page: Red Hat Assesment

There is a section for RedHat 7 administration. I haven't tested it yet and it is unclear is it suitable for EX200 (RHCSA) or EX300 (RHCE).

There are many dumps for RHCSA and not many for LFCS. Since they overlap I will use RHCSA dumps. And try to follow LFCS exam objectives as much as possible.

Vagrant

Vagrant is an open-source software product for building and maintaining portable virtual software development environments,^[4] e.g. for VirtualBox, Hyper-V, Docker, VMware, and AWS which try to simplify software configuration management of virtualizations in order to increase development productivity. Vagrant is written in the Ruby language, but its ecosystem supports development in almost all major languages.

Vagrant is a nice tool and I really like it. Starting using Vagrant is simple but it can lead problems. The problems are not Vagrant related because the software is nice, but how other people support it.

I used it with Virtualbox and I will list some nice things and bad things related to the experience. The base of using vagrant is a box (compressed disk image file)

Nice things:

• Easy to run a box
• Good documentation
• Lovely integration with Ansible (dynamic discovery)
• support for multiple virtual machines
• virtual machine customization
• no demand for using the Ruby programming language (but it can help)
• networking works out-of-the-box
• private networking (connecting to assigned IP from the host)
• greate user base with excellent "boxes"

Bad things:

• Creating boxes is a complex process
• Official boxes are broken (Ubuntu 16.04)
  Since it doesn't contain vagrant user functionality is limited and problematic
• Links to boxes are not valid or not valid anymore
• Some official boxes don't integrate virtualbox add-ons which can cause issues
• Experimentation is needed to find suitable boxes
• It doesn't use cloning feature of virtualbox and therefore if we use many virtual machines base box get expanded as many machines as we have
  

Vagrant is a nice tool that needs to be examined more. In following blog entries I will explain multi-machine setup.

psqlrc (psql startup file) in Windows

We can have startup script in Windows and Linux when running psql (Postgresql command line interface). By using Postgresql documentation is obvious for Linux but for Windows it is not.

In windows there is cryptic notes %APPDATA%\postgresql\psqlrc.conf.

So let's explore what does it mean.

APPDATA is environment variable for Windows OS and we can get it very easily.

We open command line (CMD) and type following: echo %APPDATA%.

In Windows 7 some like this will be visible on the screen:

c:> cd C:\Users\User\AppData\Roaming (User is active user)

So when we combine the appdata directory and postgresql we get following:
C:\Users\User\AppData\Roaming\postgresql

So if we want to go to that directory we need to enter following command:
cd C:\Users\User\AppData\Roaming\postgresql

We can also go to that diretory if we write in the command line:
C:> CD %APPDATA%\postgresql

The latter way is much easier and we don't need to think about name of the user.

So now when we are in the folder and we try to list the files we notice that there is not psqlrc.conf file. Does it mean that we are in the wrong folder, not. We need to create a file. I recommend any text editor will do the job, not MS Word or LibreOffice Writer. Text editor like Notepad will do the job. 

So now that when we configured the setup file how we can use it or not to use it.
If we want to use it we run the usual syntax for runnig psql program psql -U postgres 
Or if we don't want to use configuration file we need to use -X when invoking command
so it looks like this: psql -X -U postgres

Usually we don't need password for postgres (configured in pgpass.conf). I'll write about it in some another blogpost.

There are great blogs about psql online, some research will do.
Some useful pages for customization:
psql official documentation
psqlrc psql startup file for postgres
psqlrc file for dbas
how to customize the postgresql prompt with psqlrc on ubuntu 14.04

My main motivation for configuring psqlc was setting null automatically and changing default editor to vim, so I have everything in the console.
Since I am Vim user this helps me to practice server like environment. That file is temporary and it last while session lasts. If you want normal file run: 
#\! vim perm.sql  and perm.sql file will be created in the directory where you started psql

Example of my psqlrc.conf:

\set QUIET 1

\x auto
\timing
\set COMP_KEYWORD_CASE upper

\pset border 2
\pset null <NULL>
\setenv editor 'c:\\Program Files\\Vim\\vim74\\vim.exe'
\set VERBOSITY verbose

\set QUIET 0

\echo 'Welcome to PostgreSQL! \n'
\echo 'Type :version to see PostgreSQL version \n'
\echo 'Type :extensions to see the available extensions'

\set version 'SELECT version();'
\set extensions 'select * from pg_available_extensions;'

Working with directories in Docker using Windows 7 x64

This example was performed by using Docker Windows CLI 1.8.1

I will use linux shell on Windows.
The easiest way to run a shell is by installing Git with Unix tools.

Mounting directories from Windows host to Docker

 We need to put our directories into c:\Users\ directory. 
 docs: https://docs.docker.com/userguide/dockervolumes/ 
(Mount a host directory as a data volume)

There is a slight change when working in shell that worked in my case is that extra / need to be put.
So the following command mounts a directory from a host 

docker run -v //c/Users/directory:/directory image-name command

note: the volume is mounted temporary, you need to copy is into other directory,
or you can use docker cp command to copy data from host to container

Running docker with working working directory

We have the same problem as when  mounting directory.
That means we need to add extra / to run a directory from the container.
If don't do it a directory from host machine will be demanded.

This is example for first level directory in docker image

docker run -d -w //directory docker-image command


For initial startup with docker toolbox in Windows 7
Docker-machine on Windows 7 x64 

docker-machine on Windows 7 x64

I suppose you would like to use Docker toolbox on Windows 7 x64.
Boot2Docker is deprecated and new way of using Docker on Windows is docker-machine command.

If you are following official documentation they use one very cool command that sets environment variables in your shell automatically eval "$(docker-machine env machine-name)".
And then you get an error:
'eval' is not recognized as an internal or external command,
operable program or batch file.

Well, you think that there must be a command that is not on the path.
Unfortunately this is not also the case.

Uh, another linux on the Windows system.

Solution is quite simple.
1. Install Git for windows (include Unix tools) and run command prompt
    Be sure to enable PATH for git commands  
2. run sh -li (interactive shell)
3. your command line will change into linux shell
4. run above mentioned command:
    eval "$(docker-machine env machine-name)"

I have found out that usually there are usually some missing steps in the tutorials.

Well, well, something is missing here.
It seems that machine name is missing..

Ok, here is complete example from creating a new machine and connecting to it.

1. c:\Users\Name\sh -li (runs shell)
2. Name@Computer-Name ~ docker-machine create --driver virtualbox dev
3. Name@Computer-Name ~ eval "$(docker-machine env dev)"

Now your console is ready to use docker command on dev machine