Tag: sysadmin

Alive: shell script for alive monitoring using PING

2021/05/26 No Comments

Reading time: 15 – 24 minutes

Simple shell script based on bash which monitor a host with command line ping. Just bash and ping are the unique dependencies. Only state change are going to be printed:

#!/bin/bash

IP="THE_IP_TO_MONITOR"
STATE="offline"

show_state()
{
  echo "$(date '+%Y-%m-%dT%H:%M:%S') - " + $STATE;
}

while true;
do
  ping -c 4 $IP > /dev/null 2>&1
  if [ "$?" = "0" ]; then
    if [ "$STATE" = "offline" ];
    then
      STATE="online"
      show_state
    fi
  else
    if [ "$STATE" = "online" ];
    then
      STATE="offline"
      show_state
    fi
  fi
  sleep 10
done

Get Linux system process list without ‘ps’ command

2019/11/27 No Comments

Reading time: 2 – 4 minutes

When you work with embedded systems sometimes you would feel happy to have a Linux box until you discover there are plenty of basic things that you don’t have available, the extreme of that could be the ‘ps’ command which is used most of the time for checking if any process is running . Maybe you know that thanks the /proc filesystem there is access to the source of the information.

Keep next command close for solving this inconvenience he next time:

find /proc -mindepth 2 -maxdepth 2 -name exe -exec ls -lh {} \; 2>/dev/null

Convert JSON file to YAML file using CLI

2019/08/12 No Comments

Reading time: 4 – 6 minutes

Just a cookbook about how to get a YAML file when you have a JSON one.

python -c 'import sys, yaml, json; yaml.safe_dump(json.load(sys.stdin), sys.stdout, default_flow_style=False)' < file.json > file.yaml

Nested byobu, re-assigning shortcuts

2019/06/11 No Comments

Reading time: 7 – 11 minutes

I’m a byobu user for a long time, I love it for many reasons. But this is just a quick tip for extreme users like me. I mean people who use byobu for local consoles with remote byobu sessions running on top of SSH, for instance.

When prefix key combinations has to be sent to the remote host we have to press “Control + a + a” and finally the command that we want to send to the remote systems. This is not comfortable many times. So, I modified my configuration file for changing the prefix when I want to send remote commands to the nested byobu.

This is going to work this way:

Control + a

Control + b

Take a look on this screen capture where you can see byobu status bars stacked.

If you find useful the configuration that I described the only thing that you have to do is modify the configuration file: ~/.byobu/keybindings.tmux

unbind-key -n C-a 
set -g prefix C-a
set -g prefix2 F12
unbind-key -n C-b 
bind-key -n C-b send-prefix

I hope this is useful as it is for me.

Portable FTP server for Windows

2018/06/06 No Comments

Reading time: 2 – 2 minutes

Usually, simple things are the best, in the case I want to recommend an FTP server for Windows. This is a really simple but super useful FTP server for Windows. I’m using in Windows 10 and it works perfectly. Configuration is done in less than 10″ and installation is not required, I love that. Super portable.

Don’t expect sophisticated options but the most useful and advanced ones are there. If you need something like that my recommendation is:

Quick’n Easy FTP Server Lite by Pablo Software Solutions

Just a summary and extracted from the product webpage this is a summary of features:

Simple, intuitive and cool looking user interface, with several pages for managing the users, configuration and security.
Easy to setup using the build-in FTP Server Setup Wizard.
Add new user accounts with the User Account Wizard.
Support for systems that are a part of a network with a router and/or firewall.
Configuration is saved in XML format.
Realtime server trace, which displays every command and it’s reply on the screen.
Everything can also be logged to a file.

Screenshots are always lovely, some of them are:

[ngg_images source=”galleries” container_ids=”2″ display_type=”photocrati-nextgen_basic_thumbnails” override_thumbnail_settings=”0″ thumbnail_width=”200″ thumbnail_height=”150″ thumbnail_crop=”1″ images_per_page=”0″ number_of_columns=”0″ ajax_pagination=”0″ show_all_in_lightbox=”0″ use_imagebrowser_effect=”0″ show_slideshow_link=”0″ slideshow_link_text=”[Show as slideshow]” order_by=”filename” order_direction=”ASC” returns=”included” maximum_entity_count=”500″]

Finally just say THANKS Pablo for such good job and so useful stuff.

HTTPie – command line HTTP client

2018/05/02 No Comments

Reading time: 4 – 6 minutes

I imagine you are used to using curl for many command line scripts, tests, and much more things. I did the same but some weeks ago I discovered HTTPie which is the best substitute that I’ve ever found for curl. Of course, it’s also available for a lot of Linux distributions, Windows, and Mac. But I used it with docker which is much more transparent for the operative system and easy to update. To be more precise I use next alias trick for using this tool:

alias http='sudo docker run -it --rm --net=host clue/httpie'

Official website: httpie.org

Let me paste some highlights about HTTPie:

Sensible defaults
Expressive and intuitive command syntax
Colorized and formatted terminal output
Built-in JSON support
Persistent sessions
Forms and file uploads
HTTPS, proxies, and authentication support
Support for arbitrary request data and headers
Wget-like downloads
Extensions
Linux, macOS, and Windows support

From the tool webpage a nice comparison about how HTTPie looks like versus curl.

Linux: Mounting file as a partition

2018/03/21 No Comments

Reading time: 1 – 2 minutes

When we have a file with a ‘dd’ of a full disk and we want to mount a partition of that disk, we have to use an offset for jumping to the beginning of the partition that we want to mount.
Using ‘fdisk’ command we can find the partitions of that disk copied inside a file.

fdisk -l FILE_WITH_DISK_INSIDE

Once partition table is shown there is a column called ‘Start’ using the corresponding number in this column for the partition that we want we can obtain the offset required for our mounting point. Reasoning behind that is multiply start sector per number of bytes per sector.

# OFFSET = START * 512
mount -o ro,loop,offset=OFFSET FILE_WITH_DISK_INSIDE /mnt

I hope thanks to this technical note next time that I forget how to get the offset I find it fastly.

UPDATE 2018/08/29:

If you don’t want to do that manually, there is a small tool called losetup which maps the partitions of a disk image on a file.

# example, attaching partitions to loopback devices
losetup -P /dev/loop0 DISK_IMAGE
# just mount the devices now, they are /dev/loop0pX where X is the number of the partition
# dettach this assignament:
losetup -d /dev/loop0

ngrok – service which solve services behind NAT issues

2018/01/24 No Comments

Reading time: < 1 minute This is another short entry, in this case for recommending a service which we solve typical problem solved using a DNAT. Once we have a service on our laptop, or on a private server and we have to expose that service on the internet for some time or permanently usually we have to go the firewall, or router and create a NAT rule forwarding a port. This is a simple and powerful service which is going to solve that for you. There is a free account for understanding and testing the service, other plans are available and especially affordable for professional requirements.

ngrock.com

I was frogetting to say it’s compatible with Linux, Windows and Mac.

Spark Post: Mail relay host for mailings

2017/05/05 No Comments

Reading time: 1 – 2 minutes

This is going to be a very short post entry, I just want to refer a very interesting mail relay (smart host) which define itself like:

Email delivery services built for developers, by developers
Combined with your language of choice, using the power of our robust cloud API couldn’t be easier.

Open a SparkPost account today and send up to 100.000 emails per month for free. The best is you can do using SMTP or using a REST API; really nice easy to use an powerful control dashboard simplify externally keys management, statistics, templates for mailings, and many more features.

Personally I love the service because is extremely useful to be configured on SSMTP service of Linux as a default relay host, for personal and professional use. Another use could be to check end-to-end mail services.

Personally I love the service, and if you want to send really big mailings theirs costs are very competitive.

Upgrading Redmine in a nutshell

2017/04/28 No Comments

Reading time: 14 – 23 minutes

I use Redmine to track my personal projects, and every time that I have to update I have to re-read the full upgrading page which is long and full of exceptions. So I decided to write my own reduced cookbook to solve that. FYI I’m using Ubuntu 16.04, Apache2, MySQL and Passenger for running Redmine.

Being root user run:

backup MySQL database

download new redmine package and unpack in /var/www

change ‘redmine’ soft link to new folder

copy old files and directories overwriting the new ones:<br><pre><code>config/database.yml<br>config/configuration.yml<br>files/<br>plugins/</code></pre><br>

locating work directory on new redmine folder, run:<br><pre>bundle install --without development test<br>bundle exec rake generate_secret_token<br>bundle exec rake db:migrate RAILS_ENV=production<br>bundle exec rake redmine:plugins:migrate RAILS_ENV=production<br>bundle exec rake tmp:cache:clear tmp:sessions:clear RAILS_ENV=production</pre><br>

restart apache server