Tag: ubuntu

Tips for new Ubuntu Users

David Craddock

Here are some extra tips if you’re just getting started out on Ubuntu.

  1. You don’t have to go through the UI to shut down or reboot your computer. You can do it from the command line. The commands are: 
    sudo reboot # to reboot
sudo poweroff # to shut down and power off the computer
  2. You can get a lot more information on your computers startup and shutdown sequences by removing the default Ubuntu splash screen that obscures this. You should definitely do this if you want to learn more about what your system is
    actually doing under the hood, especially if you need to troubleshoot what it’s doing. To do this:

    sudo nano /etc/grub/default/grub
# find the line where it says GRUB_CMDLINE_LINUX_DEFAULT and remove 'quiet splash' 
# from this variable. If that leaves the variable empty make sure it is
# still set as an empty variable, e.g. GRUB_CMDLINE_LINUX_DEFAULT=""
sudo update-grub
sudo reboot

    Now you will see everything that is happening when your system starts up and
    shuts down, or reboots.

Google Drive Backup using Rclone

David Craddock

For 8 TB of data storage on Google Drive, plus my own Google organization, I am paying £30/month, which is a pretty good deal.

I wanted to use this space for backing up my NAS, but it was proving difficult. The program I was recommended for Linux backup, Duplicati, was not the best for this purpose. My backup runs would not complete, they would be slow, and full of syncing errors.

Until I discovered rclone.

rclone was much better than Duplicati at backing up my NAS to Google Drive.

This is the script I use to sync the NAS content to Google Drive: https://github.com/wordswords/dotfiles/blob/568a8768154de8609a01b26560373ec5ca0eab85/bin/rclone-backup.sh

It works just like rsync, but with a progress indicator. I’ve added it to my crontab and it syncs everything up weekly.

Setting up Enlightenment window manager on Ubuntu 21.10

David Craddock

Enlightenment is a very underrated window manager choice, in my opinion. It still looks very pretty and is very configurable. There is a packaging bug with the latest version of Enlightement in the 21.10 repo which means it doesn’t work correctly. The fix is to set the suid bit on the ‘enlightenment_system’ binary. So:

  1. sudo apt install enlightenment
  2. sudo find /usr/lib -type f -name enlightenment_system -exec sudo chmod 4755 {} \;
  3. Log out of Ubuntu
  4. Click the settings cog in the bottom right to change your Window manager to enlightenment
  5. Log on and the settings wizard will help you configure Enlightenment

Setting up Kindlefire HDX for Development under Ubuntu 12.04

David Craddock

amazon_kindle_fire_hdx1

I wanted to get a Kindlefire HDX running under Ubuntu 12.04 with adb.

First I needed to setup the udev rules:

1. Edit /etc/udev/rules.d/51-android.rules as root, and add the following line (create this file if it does not exist):

SUBSYSTEM=="usb", ATTRS{idVendor}=="1949", MODE="0666"

2. Change the permission of this file by executing the following command as root:

chmod a+r /etc/udev/rules.d/51-android.rules

3. Reload the rules by executing the following command as root:

udevadm control --reload-rules

4. Run these commands to restart adb:

adb kill-server
adb start-server

5. Now when I run 

lsusb

I can see the device listed.

6. Next I needed to enable adb access on the Kindlefire HDX device itself by going to Settings -> Device -> Enable ADB.

7. Finally I could run: 

adb devices

within Ubuntu and have it recognise the Kindlefire HDX.

Android Debug Bridge failing to detect emulators under OSX

David Craddock

Android

I’ve been working on a project at the BBC where we are using the Android command-line tools from the Android Developer Tools, to spin up and terminate series of emulators. I noticed a big problem under OSX where ‘adb devices’ was failing to register emulators occasionally when we started them up, without any error message, even though they were loaded and quite clearly running in a window on OSX. This was a real problem for our project because we needed absolute parity between emulator process being launched and subsequently being detected by adb.

We switched to using adb with emulators in an Ubuntu 12.04 VM running under OSX, and we had no further problems with our setup. Emulators will now be programatically launched and torn down by our monitoring application. We now have an array of emulators which we can deploy to at will, which is very useful.

I don’t know what has caused this problem, my only hunch is that the Android toolkit was probably developed in a very Linux-heavy environment, and so adb on Linux was probably their first testing platform. All I can say is that Linux is much more stable than OSX, even as a VM, for Android emulation.

VirutalHosts on CentOS

David Craddock1 Comment

A common task when setting up an Apache webserver under Linux, is writing a httpd.conf file. The httpd.conf file is the main configuration file for Apache. One of the main reasons to edit the httpd.conf file is to setup virtual hosts In Apache. A Virtual host configuration allows several different domains to be run off a single instance of Apache, on a single IP. Each host is a ‘Virtual host’, and typically has a different web root, log file, and any number of subdomains aliased to it. The virtualhosts are configured in parts of the httpd.conf file that look like this:


    ServerName myserver.co.uk
    ServerAlias www.myserver.co.uk
    ServerAdmin me@myserver.co.uk
    DocumentRoot /var/www/html/myserver.co.uk
    ErrorLog logs/myserver.co.uk-error_log
    CustomLog logs/myserver.co.uk-access_log common

Now on Ubuntu, virutalhosts are made easy. The httpd.conf is split into several files. Each virutalhost has a different file in /etc/apache2/sites-available. When you want to activate a particular vitualhost, you create a symbolic link from /etc/apache2/sites-enabled/mysiteto /etc/apache2/sites-available/mysite (if you wanted to call your site configuration file ‘mysite’). When apache boots up, it loads all the files it can find in /etc/apache2/sites-available/* and that determines which virutalhosts it loads. If there is not a link from /etc/apache2/sites-available/ to your virutalhost file, it won’t load it. So you can easily remove the links in /etc/apache2/sites-available without deleting the actual virutalhost file. Therefore you can easily toggle which virtualhosts get loaded.

CentOS uses a different structure. Everything is lumped into /etc/apache/httpd.conf. So there is no way to easily toggle virutalhosts on/off, and everything is a bit more chaotic. I’ve just had to setup a new CentOS webserver, and I struggled for a bit after being used to ubuntu-server. Here’s a format you can use if you’re in the same boat, and you have to setup httpd.conf files for CentOS:

NameVirtualHost *:80 # this is eseential for for name-based switching

# an example of a simple VirtualHost that serves data from 
# /var/www/html/myserver.co.uk to anyone who types in
# www.myserver.co.uk to the browser

  ServerName myserver.co.uk
    ServerAlias www.myserver.co.uk
    ServerAdmin me@myserver.co.uk
    DocumentRoot /var/www/html/myserver.co.uk
    ErrorLog logs/myserver.co.uk-error_log
    CustomLog logs/myserver.co.uk-access_log common 


# an example of a VirutalHost with apache overrides allowed, this means you can use
# .htaccess files in the servers web root to change your config dynamically

    ServerName bobserver.co.uk
    ServerAlias www.bobserver.co.uk
    ServerAdmin me@bobserver.co.uk
    DocumentRoot /var/www/html/bobserver.co.uk
    ErrorLog logs/bobserver.co.uk-error_log
    CustomLog logs/bobserver.co.uk-access_log common
 
  
      AllowOverride All
  
  
      AllowOverride AuthConfig
      Order Allow,Deny
      Allow from All
  


# an example of a VirutalHost with apache overrides allowed, and two subdomains
# (mail and www) that both point to the same web root

  ServerName fredserver.co.uk
    ServerAlias www.fredserver.co.uk
    ServerAlias mail.fredserver.co.uk
    ServerAdmin me@fredserver.co.uk
    DocumentRoot /var/www/html/fredserver.co.uk
    ErrorLog logs/fedserver.co.uk-error_log
    CustomLog logs/fredserver.co.uk-access_log common
 
  
      AllowOverride All
  
  
      AllowOverride AuthConfig
      Order Allow,Deny
      Allow from All
  


# .. etc

With the above structure, you can add as many VirutalHosts to your configuration as you have memory to support (typically dozens). Apache will decide on which to choose based on the ‘ServerName’ specified in each VirtualHost section. Just remember to add that all-important NameVirtualHost: *:80 in the beginning.

Once you’ve got your httpd.conf file the way you like it, be sure to test it before you restart apache. If you restart apache and your httpd.conf file has errors in it, Apache will abort the load process. This means that all the websites on your webserver will fail to load. I always use apachectl -t or apache2ctl -t before I restart. That will parse the httpd.conf file and check the syntax. Once that’s OK, then you can issue a /etc/init.d/httpd restart to restart Apache.