Docker Quick Reference

This post is for me a place where to store notes about Docker. I hope that this can be helpful for you.

Basic usage

How do you disable auto-restart on a container? (Ref.)

docker update --restart=no my-container

How can we see all possible variables for a format?

docker container ls -a --format '{{json .}}'

How to analyze disk usage of a Docker container ? (Ref.)

docker ps --size

or

docker system df --verbose

Vim Quick Reference

Basically, vim has three working modes:

1. Command mode
   
2. Insert Mode
   
3. Ex-mode
   

Basic VIM Movement

• b move back from word
• w move next to word

Commands

Disable text wrap

:set wrap!

(you can use ~/.vimrc)

Display or hide line numbers?

:set number

for display

:set nonumber

for hide

VMWARE - Get snapshots and size of VMs

Today I need to check the snapshots of all VMs of a VMware infrstructure. Unfortunately I have found that with vSphere Client and vSphere Web Client it's not possibile to get a list of snaps associated to VMs.

So, after a advanced google search, I have found that this is possibile using VMware PowerCLI tools.
I've installed the version 5.5 available in this page https://code.vmware.com/web/tool/5.5/vmware-powercli

After this, I use powershell for loading the snapin and connect to my vcenter server with this:

add-pssnapin vmware.vimautomation.core
connect-viserver myvcentersrv_FQDN

Then with the commmand I get the list with VM name, number of snapshot and size:

Get-VM | Format-Table Name, @{Label="NumSnapshots";Expression={(Get-Snapshot -VM $_ | Measure-Object).Count}}, @{Label="TotalSnapShotSizeMB";Expression={(Get-Snapshot -VM $_ | Measure-Object -Sum SizeMB).Sum}}

Ref: http://www.vhersey.com/2016/03/01/quick-powercli-to-get-snapshots-and-size/

Pip Quick Reference

Basic pip usage

Upgrade PIP

python -m pip install --upgrade pip

Find outdated/updatable pip packages

pip list --outdated

Git Hooks - A way to automate deploy tasks

During my work I use git for automate the deploy on production system. Sometimes I need execute some command or script immediately after checkout. Git has a very powerful mechanism called hooks (you can read more about it on official documentation follow this link).
On client side to install hooks what you have to do is to create a dir called hooks under .git/ . But  you do not have to do any of this because when you have initialized your project git create it for you.
If you list the content of hooks dir you can found a list of samples script to use (all of them are bash scripts). Most of this script start with the prefix  pre- or post- followed by action name.
The script that I found helpful is post-checkout that is automatically executed after a successful git checkout. My post-checkout script contain commands for adjust permissions on files and ask to restart web server.

#!/bin/bash
git ls-files -z --with-tree="$2" --directory | xargs -0 chmod o-rxw --
git ls-files -z --with-tree="$2" --directory | xargs -0 chown www-data:www-data --
find . -type d | xargs -I {} chown www-data:www-data {}
find . -type d | xargs -I {} chmod o-rwx {}
exec < /dev/tty

while true;
   do
      read -p "Do you want to restart apache?  [Y/N]:" choice
      case "$choice" in
         y|Y) service apache2 restart;break;;
         n|N) break;;
         *) echo "invalid" && break;;
      esac
   done

Remember to add execute permission to this script or git won't execute it after the checkout.

Git Handbook

How to setup git with SSH Key

# git remote set-url origin [email protected]:<Username>/<Project>.git

Windows CRLF chars.

Su windows bisogna disattivare questa funziona altrimenti non funzionano i caratteri CRLF.

# git config core.autocrlf false

How can I debug git/git-shell related problems?

If you have problem with Git and you need to debug you can run this:

# GIT_CURL_VERBOSE=1 GIT_TRACE=1 git pull

Ref: https://stackoverflow.com/questions/6178401/how-can-i-debug-git-git-shell-related-problems

How to get list of files between change log ?

If you need to get list of files (included directory tree) from change list you can use:

# git diff-tree -r --name-only 2c636a^ 5b47402 | xargs -I {} rsync -aR {} output/

Delete files from git index when they are already deleted

# git ls-files --deleted -z | xargs -0 git rm

How do I show my global git config?

# git config --list

Show remote branches

# git branch -vr

Filename too long in git for windows

git config --system core.longpaths true

Note: You need to run as administrator.
Ref: https://stackoverflow.com/questions/22575662/filename-too-long-in-git-for-windows

List log with tag date

git log --date-order --graph --tags --simplify-by-decoration --pretty=format:'%ai %h %d'

Configure username and mail

# git config --global user.name "Name Surname"
# git config --global user.email "mymail(at)mydomain.com"

How to improve reading of log files

There are hard times when a sysadmin have to read a lot of rows of log files for troubleshoot a system error. In this times can be helpful to use some tools to improve reading of these files.

I've found two tools:

• Generic Colouriser (GRC) - https://github.com/garabik/grc - there are programs: grc and grcat. The main is grcat, which acts as a filter, i.e. taking standard input, colourising it and writing to standard output. Then you can use configuration files for customize color ouput depend on you application output log. 
• Log File Navigator (LNAV) - http://lnav.org/ - this is a real log file navigator that parse content of file and follow the stream for read latest lines. Lnav can help highlight the parts that are important and filter out the noise. 

How to launch python Idle from a virtual environment (virtualenv)

If you have a virtual environment and you want to use IDLE for write you pretty script you can run this command:

# python -m idlelib.idle 

Ref: https://stackoverflow.com/questions/8792044/how-do-i-launch-idle-the-development-environment-for-python-on-mac-os-10-7/8792082#8792082

How to view all ssl certificates in a bundle?

This morning I got a problem with a certificate bundle and how to get single certificate inside it.
I found the answer on ServerFault (link).

# openssl crl2pkcs7 -nocrl -certfile bundle.crt | openssl pkcs7 -print_certs -text -noout

Sed Quick Reference

Basic sed usage

Add "-dev" at the end of the match.

# sed -i 's|saml[1-2]-.*\.php/[a-zA-Z0-9\-]*|&-dev|