AP CS Principles - The College Board Gets It Right

Beginning this Fall, students in high schools across the United States were able to will be able take a new course - AP CS Principles.  I can't say I've always been a big fan of the College Board and the impact this very powerful institution has on education in my country. I have to say, however, that I think they got it right this time. From my experience thus far, I am a huge fan of the new CS Principles course.

Working with the NSF, the College Board has approved three on-line curricula for the launch this Fall:

• The Beauty and Joy of Computing
• Mobile CSP
• Thriving in Our Digital World

Last Spring I used the Mobile CSP curriculum with students who were taking dual-enrolled CSC 200: Introduction to Computer Science with me through Northern Virginia Community College.  While I haven't researched the details of its history, it is obvious that CSC 200 was created by the Virginia Community College System (VCCS) to receive credits from the new AP CS Principles course.

As a free software activist of many years, I found little gems inside the Mobile CSP curriculum that let me know kindred spirits where involved in its creation:

This Fall I am again teaching CSC 200 using Mobile CSP. The more I use App Inventor the more I love it.  While I've been too busy to keep up with this blog of late, it is time to get back to more regular posting so I can document our experience this year with this wonderful new curricula.

My Annual Love Letter to SchoolTool

It is the end of August, and time once again for me to setup my SchoolTool instance for the coming school year. Each year for the last several years, I have sent an email to the SchoolTool mailing list expressing both my joy and my deep felt gratitude at the pleasure I experienced setting up my very own student information system (SIS).  Sadly, we may have come to the end of an era, and SchoolTool's days may be numbered, so I felt it more appropriate this year to express my gratitude here in my blog.

The reason I feel compelled to write a "love letter" to the SchoolTool developers each year is that they have made the very complex process of setting up an SIS smooth and painless, both by the design of the software itself, and by the wonderful SchoolTool Book written by English teacher and former project manager, Tom Hoffman.  It provides a model of what technical documentation should be, and the influence that the documentation process and the user interface design process had on each other is apparent. With nothing more than the book to guide me, I can create a school year, populate it with courses, sections, terms, time tables, instructors, students, and skills. In just a few minutes I am ready to start the new school year. The ease with which everything works is a total thrill!

I teach dual-enrolled high school / community college classes in a career and technical school in Arlington, Virginia. The SIS provided by Arlington Public Schools is not setup to properly handle the odd configurations of overlapping high school and college classes that I need to make my CS / IT program work.  SchoolTool provides me with a customizable SIS that meets my needs, while providing a host of added benefits to my students.  The CanDo Skills Tracking system lets students see their progress on the explicit skills they are expected to acquire in my classes. The SchoolTool Quiz component enables me to create custom tests and quizzes automatically linked to the skills tracking system.

SchoolTool will forever epitomize what free software means to me and why I've dedicated much of my energy over the past 20+ years fighting for software freedom. It was created in an open process with input throughout by the real users of the system.  I became one of those users back in the Summer of 2005, when I met Tom Hoffman at Pycon and began the collaboration that continues to this day. Both the CanDo and Quiz components were added at the initiative of a small group of us in Virginia, and students of mine contributed directly to the development of both components. There is still no other software, either free or proprietary, that does what SchoolTool does.

The development of SchoolTool was driven by the desire to provide use value and to create a tool to help change the world, specifically by positively impacting education in Africa and the developing world. Thanks to the sponsorship of Mark Shuttleworth, it was freed from the imperative of commodification for an extended period of time. It never could have developed the innovations it has otherwise.

Some big mistakes where certainly made along the way to SchoolTool's development, the biggest of which is probably building SchoolTool on a dead end web application framework, Zope 3, which has now isolated SchoolTool from the larger free software development community. That mistake may cause SchoolTool to follow its framework into abandonment. You never can tell with free software projects, however, since they can be taken up by anyone at any time who finds them useful.  Perhaps SchoolTool will find new life in some unexpected way, or perhaps some of its innovations will find their way into another free software SIS.

I am just happy that it will be available for at least the next several years on Ubuntu servers.  I plan to keep using it for as long as I can, since it is a tremendously effective resource to help my students monitor their learning, and since I get to experience the joy and excitement each year of setting it up!

Setting Up a RHCSA Practice Laptop - Part 1

In order to practice for the RHCSA at home, I took an old Dell Latitude E6500 with 4GiB of RAM and purchased a 500GiB hard drive on which I could install CentOS 7 with a server GUI as the base operating system and them multiple virtual machines using KVM with which to experiment and learn.

My package selection for the install was a Server GUI installation. I partitioned the hard drive with 1 GiB of swap, 500 MiB on a standard partition for the /boot, and 30 GiB for the root partition.

I also created a 60 GiB partition for /home, and then allocated everything that remained (375.27 GiB) to /var.  The reason for giving some much space to /var is that the default KVM / qemu setup on CentOS 7 places virtual hard drive images in /var/lib/libvirt/images, so I wanted plenty of space available for multiple images.

After the install finished I wanted to see what the partitions looked like, so I ran

$ sudo yum install system-storage-manager

and then

$ sudo ssm list

which revealed the following:

-----------------------------------------------------------------
Device        Free       Used      Total  Pool        Mount point
-----------------------------------------------------------------
/dev/sda                       465.76 GB              PARTITIONED
/dev/sda1                      500.00 MB              /boot
/dev/sda2  0.00 KB  465.27 GB  465.27 GB  centos
-----------------------------------------------------------------
--------------------------------------------------------
Pool    Type  Devices     Free       Used      Total
----------------------------------------------------
centos  lvm   1        0.00 KB  465.27 GB  465.27 GB
----------------------------------------------------
--------------------------------------------------------------------------------
Volume           Pool   Vol size  FS   FS size    Free      Type   Mount point
--------------------------------------------------------------------------------
/dev/centos/swap centos 1.00 GB                             linear
/dev/centos/root centos 30.00 GB  xfs  29.99  GB  26.73 GB  linear /
/dev/centos/home centos 60.00 GB  ext4 60.00  GB  55.88 GB  linear /home
/dev/centos/var  centos 374.27 GB ext4 374.27 GB 349.02 GB  linear /var
/dev/sda1               500.00 MB xfs  493.73 MB  293.59 MB part   /boot
--------------------------------------------------------------------------------                                                                          

To be continued in Fall of 2016..

Resources

• How to manage LVM volumes on CentOS / RHEL 7 with System Storage Manager
• KVM Virtualization in RHEL 7 Made Easy

Moving an ArcGIS File Geodatabase to QGIS

I am taking GGS 553: Geographic Information System this semester at part of my graduate studies at George Mason University.  In a previous post I described how I ended up in this Geographic Information Science graduate certificate program, which I have now been pursuing for almost 2 years.  GGS 553 is a required course, and the first one in the program that has required me to use proprietary software, since much of the course is focused on learning to use ArcGIS.

I am both philosophically and ethically opposed to proprietary software, since it runs dead against the expansion of our shared cultural space, which I believe is vital to the survival of our species. This is a required course, however, and in the large scheme of things I am willing to compromise when I need to. I like to think of it as dancing with the devil, learning the devil's moves in order to be able to freely out dance him in the future. In this case that will mean applying what I learn in GGS 553 to mastering QGIS, the free software alternative to ArcGIS. I had intended to try to do each of our assigned labs this semester in both ArcGIS and QGIS, but when I found it difficult enough just to complete them on time in ArcGIS, I gave up on that idea after the first week.

This week we have a sort of half size assignment, so I thought I would use the extra time available to see if I could do it in QGIS.  The first challenge will be to load the project data into QGIS.  We were given the data in ArcGIS's file geodatabase format. QGIS can not yet read and write to this format directly, but there are tools available to convert it into PostGIS, with which QGIS can work well.

Last Summer I wrote a blog post documenting how I setup a PostGIS server on Ubuntu 14.04.  Since this year I am also needing to learn RHEL, I'll use this guide to setup the server on the little Centos 7 server I have at home for just such purposes, and then connect to it from QGIS running on my Ubuntu desktop.

Installing a PostGIS Server on Centos 7

$ sudo yum install postgis postgresql-server postgresql-contrib
$ sudo postgresql-setup initdb
$ sudo -i -u postgres
$ psql
postgres=# \password postgres
Enter new password: 
Enter it again: 
postgres=# \q
$ exit
$ sudo vi /var/lib/pgsql/data/pg_hba.conf

Change this line (near the bottom):

host    all             all             127.0.0.1/32            ident

to this:

host    all             all             0.0.0.0/0               md5

Next allow database connections from outside:

$ sudo vi /var/lib/pgsql/data/postgresql.conf

Change:

#listen_addresses = 'localhost'

to this:

listen_addresses = '*'

Create a new database user with superuser privileges:

$ sudo su - postgres
$ createuser --superuser [user]
$ psql -c "ALTER ROLE [user] PASSWORD '[password]'"
$ exit

Then as that user create the database and add gis extensions:

$ createdb webster
$ psql -d webster -c 'CREATE EXTENSION postgis'

Then after copying over the Webster.db directory containing the file geodatabase, I ran:

$ ogr2ogr -f "PostgreSQL" PG:"dbname=webster user=[user] password=[password]" Webster.gdb

After which I connected my desktop QGIS to the PostgreSQL server running on my little household server and loaded the three layers I found there:

Resources

• Working with File Geodatabases (.gdb) using QGIS and GDAL
• How To Install and Use PostgreSQL on CentOS 7
• How To Set Up a Firewall Using FirewallD on CentOS 7
• How to migrate GDB data into PostGIS without ESRI apps?

Software Management with YUM

YUM (Yellowdog Updater, Modified) is the package management tool used on Red Hat Enterprise Linux and its derived versions, CentOS and Scientific Linux. It acts as a front end to the RPM Package Manager (RPM), and is used to install, remove, and update software on Red Hat based systems.

I first encountered YUM when installing Yellow Dog Linux on PowerPC based Macintosh computers back at the dawn of the 21st century.  When I switched over to Debian based GNU/Linux systems with the release of Ubuntu in 2004, I completely lost touch with the RPM world until my Spring semester Linux System Administration course's pursuit of RHCSA certification brought me back into the fold.

I am writing this post to use as a handy list of the most common things I need to do when managing software:

1. Update the software on the system
   

   $ yum check-update
   $ sudo yum update package_name
   $ sudo yum update [to update all packages]
   $ sudo yum group update group_name
   

2. List all the currently installed software
   

   $ yum list installed
   $ yum list installed "global expression"
   

3. Search for available packages
   

   $ yum list available "global expression"
   $ yum search term...
   

4. Display information about a package
   

   $ yum info package_name
   

5. Install a new package
   

   $ sudo yum install package_name
   

6. Remove an existing package
   

   $ sudo yum remove package_name
   

7. List the current repos
   

   $ yum repolist
   $ yum repolist -v
   

That covers the basics. I also need to learn how to clean up the cruft that accumulates over time as a system is run, in Debian land the kind of thing that would be done with $ sudo apt-get autoremove. It seems that in RPM space that is accomplished with the package-cleanup utility, so I'll look into that.

Resources

• YUM Chapter from Red Hat System Administrator's Guide
• How to clean installed rpms using package-cleanup

Centos Command-line Tricks and Tips - Getting Rid of the Terminal Beep

Getting Rid of the Terminal Beep:

My terminal was making an annoying beeping (more like a swoosh beep, actually) every time it couldn't match a tab completion.  I like to listen to music while I work, so this was really driving me crazy.  All I needed to do to stop it was to run:

$ echo 'set bell-style none' >> ~/.inputrc

which appends 'set bell-style none' to the .inputrc file in my home directory.  .inputrc didn't exist in my home directory (I checked before running the command), so running this command created it.

• How to disable beep sound in Linux CentOS 7 command line?

After exiting the terminal and starting another, the terminal maintained the silence I wanted it to ;-)

Setting Up a Centos Router - Part 1

In order to run the kind of experiments we will need to run to really learn proper GNU/Linux system administration, we need our own "safe space" in which to play.  In previous years when I had students with the level of skills our ITN 170 group is quickly acquiring, I always used one of our machines as a NAT Router so that we could isolate our own network traffic and setup custom services within our private network space.

The basic idea is captured in the following illustration.

 

What is required is a machine with two NICs (represented here by Tux) - one which connects to the outside network and the other which connects to the local network.

Setup Process

Here is what I did to setup a basic router using an old desktop PC:

• Did a minimal install of CentOS 7 on a machine with two NICs, connecting one of the NICs to the outside network and activating this connection using DHCP on the host network during the installation process.
• Ran yum update after installation to make sure I had the current software.
• Ran yum install yum-utils vim to get vim and the package-cleanup utility. I then ran package-cleanup --oldkernels --count=1 to remove all but the current kernel package.
• I ran ip addr and got back information on three network interfaces:
  
  1. lo - the loopback interface or localhost, with its 127.0.0.1/8 network address.
  2. enp0s25 - the NIC on the motherboard which I had activated with DHCP during installation.
  3. enp3s0 - the addon NIC that was not configured during installation. It had the following information:
     

     enp3s0:  mtu 1500 qdisc pfifo_fast state UP qlen 1000
         link/ether 00:15:17:20:b6:e6 brd ff:ff:ff:ff:ff:ff
     

• I edited /etc/sysconfig/network-scripts/ifcfg-enp3s0 adding the following:
  

  TYPE="Ethernet"
  BOOTPROTO="static"
  IPADDR="192.168.114.1"
  NETMASK="255.255.255.0"
  GATEWAY="x.x.x.x"  (place your gateway adress here)
  

I used the resources linked below to try to enable IP routing and NAT, but I was not successful in getting it to route.  I have a laptop running Centos 7 connected to the router machine.  Before attempting this setup I had installed ClearOS on the router and got it to route for the laptop with a setup process using ClearOS's web interface.  An experienced friend of mine shamed me into removing this, however, by telling me he would never hire a sysadmin who only new how to set this up using a web interface.

So for now I have assigned two of my students to continue looking into it, and I'll get together with that friend who shamed me into this to get his assistance on Tuesday if we haven't figured it out by then.

To be continued...

Resources

• How to Turn a Linux Server into a Router to Handle Traffic Statically and Dynamically
• Deploy Outbound NAT Gateway on CentOS 7

Text Processing and Unix History

Preparing for the RHCSA certification is turning out to be a heap of fun! Despite more than 20 years as a free software activist and personal user of GNU/Linux systems for all my personal computing, and despite being a computer science teacher during that same time, there are a wide range of basic Unix CLI skills that I only scratched the surface of in all that time (shame on me!).

Preparing for the RHCSA is providing the opportunity to address that deficit at long last.  Chapter 4 of the book we are using in class to study for the certification is titled "Working with Text Files". The most enjoyable thing about this investigation into Unix text file processing is the view it provides into Unix history.

In the beginning there was ed.  ed begat ex, and ex begat vi... Along the way we got cousins grep and sed too.  Since grep, sed, and vi are part of the Unix admin's toolset, I want to learn to use them at least well enough to be able to help prepare students (and myself) for the RHCSA certification and to be able to present them well to future students in my ITN 170: Linux System Administration class.

Since in the beginning there was ed, let me start with that.  I found a very nice blog post, Actually using ed, which I found to be a wonderful introduction to this tool.  I set myself the task of using ed to create a list of fruits in a file named fruits.txt.  The first thing I found out was that trying:

$ ed fruits.txt

did not create the file for me, instead returning a "No such file or directory" error.  So I did the following, which worked:

$ touch fruits.txt
$ ed fruits.txt
0
a
apples
bananas
pears
apricots
kiwis
blueberries
oranges
peaches
cranberries
blackberries
pinapples
teaberries
.
w
110
q
$

After that, I ran $ cat fruits.txt, and saw that everything was as I wanted it:

apples
bananas
pears
apricots
kiwis
blueberries
oranges
peaches
cranberries
blackberries
pinapples
teaberries

Now if I want an alphabetical listing of the fruits in my list, I can run:

$ grep berries fruits.txt | sort

and see this:

blackberries
blueberries
cranberries
teaberries

RegexOne is a nice, interactive tutorial for learning basic regular expressions.  I wanted to do all the exercises using grep on the command-line as well, and in the process setup a new github repo for resources related to our RHCSA study, here.

Next I wanted to learn sed.  Sed - An Introduction and Tutorial by Bruce Barnett is a wonderful tutorial.  With so much awful document out there, it is great to find something written by someone with a grasp of how people actually learn.

Using the fruits.txt file I created with ed, I ran $ sed s/berries/cherries/ fruits.txt and got:

apples
bananas
pears
apricots
kiwis
bluecherries
oranges
peaches
crancherries
blackcherries
pinapples
teacherries

Since sed uses the same substitution syntax that vim uses, learning it will be a big help in becoming a more effective vim user as well.

QGIS Delivers Functionality and Freedom

I am taking a graduate course this semester, GGS 553 - Geographic Information System, which is required for the Graduate Certificate in Geographic Information Sciences program that I am hoping to complete.  I like the text book we are using for class, and greatly enjoyed the first lecture.  What I am not happy about is that the labs which will make up a large part of the course assignments require the use of proprietary software, specifically ArcGIS, and then by extension, the Windows operating system on which it runs.

I have been a free software activist for more than 20 years. Software for GIS makes it especially easy to state why I believe so strongly in software freedom. To put it simply, I believe software should be part of humanity's shared cultural heritage, and that all efforts to turn it instead into a commodity are immoral.

Installing ArcGIS made this painfully clear to me.  In the first place, using it required that I use a non-free operating system, so I am running Windows just so that I can use ArcGIS.  Going through the gymnastics (registering an on-line account, figuring out where to enter the product code after missing it the first time through the installation, etc.) required to establish that I was "authorized" to use the commidified resource was most unpleasant. It rubs me deeply the wrong way to see human creativity misspent making the world a worse place rather than a better one.

No matter.  I have to do it to complete this required course, so I am determined to make the best of it.  What that means to me is keeping in mind the well known quote from Sun Tzu,

"Know your enemies and know yourself, you will not be imperiled in a hundred battles."

So I'll count learning ArcGIS as knowing my enemy, and time permitting, I will do each lab assignment in QGIS in parallel.

The first thing I wanted to do was to install the latest QGIS on my Ubuntu 14.04 desktop.  To do this, using this web page as a guide, I added the following to the end of my /etc/apt/sources.list file:

# For QGIS 2.12
deb http://qgis.org/ubuntugis trusty main
deb http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu trusty main

Then I ran:

$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-key 3FF5FFCAD71472C4
$ sudo aptitude update
$ sudo aptitude install qgis

This is a much easier process than installing ArcGIS. QGIS also runs much faster than ArcGIS, and on the operating system I choose, not the one chosen for me.

It also seems that the wonderful folks who have developed QGIS have modeled its UI after the non-free standard, so the lab notes describing ArcGIS helped me understand QGIS as well. QGIS's Browser is the equivalent of ArcGIS's ArcCatalog. Here is the QGIS Browser showing the shape files from my first lab:

The QGIS Desktop functions like ArcGIS's ArcMap.  Here is QGIS Desktop with my Lab 1 shapefiles in a map:

So far, so good.  I was able to answer all the lab questions using QGIS with the given data, and I learned new things about QGIS through doing the ArcGIS lab exercises.

Creating a Shared Partition Between Ubuntu and Scientific Linux

Now that I've removed Windows from my desktop computer at work, and installed Scientific Linux in its place (note: it was, Centos 7.2 with LVM partitions, but now it is Scientific Linux 7.1 with standard partitions), I decided I needed a partition that could be shared between the two distros for large user data.

For example, I have 12 Gigabytes in my Music directory, and a number of VirtualBox hard disk images (at 20 to 30 Gigabytes each) that I would like to access from both OS's.  So my plan is to create a new partition which I will mount on /media/share on both Ubuntu and Scientific Linux.  Then I'll make symbolic links from /home/[username]/Music to /media/share/Music from each home directory.

Before I could create a new partition, I needed to shrink one of my existing partitions to free up space.  Here is how the partitions looked when I started:

and here is what they looked like after shrinking /dev/sda3, growing /dev/sda4 and inserting /dev/sda7 into the new space inside it:

I made the change by booting my computer from an Ubuntu 14.04 Live DVD and running GParted. It took about 20 minutes to shrink my home partition, but it worked without incident.

The next step is to add a mount for the new /dev/sda7 partition.  It's been several years since I played around with mounting partitions, but I still remembered that it involved editing the /etc/fstab file and adding the device and the mount point.  So I loaded my /etc/fstab file and noticed something had changed since I last looked at it:

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/sda2 during installation
UUID=4ae26245-fe59-40d2-a380-2c2de57b652b /               ext4    errors=remount-ro 0       1
# /home was on /dev/sda3 during installation
UUID=5c4e86f6-1d94-4eab-9931-5d3aa29e1583 /home           ext4    defaults        0       2
# swap was on /dev/sda1 during installation
UUID=bba8f235-d8b0-4131-9a3e-ec286c3b3837 none            swap    sw              0       0

I was completely unfamiliar with UUID, and had been expecting to see device names (like /dev/sda3 etc.) instead.  I bit of searching led me to several links:

• Why does fstab use UUID instead of the actual file system name?
• How to retrieve and change partition's UUID Universally Unique Identifier on linux
• UsingUUID
• Persistent block device naming

Running $ sudo blkid gave me this:

 /dev/sda1: UUID="b70d7272-e47f-426a-a979-5417bb2f7801" TYPE="swap"
/dev/sda2: UUID="4ae26245-fe59-40d2-a380-2c2de57b652b" TYPE="ext4"
/dev/sda3: UUID="5c4e86f6-1d94-4eab-9931-5d3aa29e1583" TYPE="ext4"
/dev/sda5: UUID="76f8dd02-3671-49ba-b75a-da6d8bb65b19" TYPE="ext4"
/dev/sda6: UUID="e7e58de9-a748-4500-b300-ae1ca10f2056" TYPE="xfs"
/dev/sda7: UUID="44244888-7000-49bf-8ac8-2c32e2f73eb5" TYPE="ext4" 

which I used to add the following line to /etc/fstab:

UUID=44244888-7000-49bf-8ac8-2c32e2f73eb5 /media/share ext4 defaults

and then ran:

$ sudo mkdir /media/share
$ sudo mount -a

which mounted /dev/sda7 on /media/share. Next I moved all my music files to /media/share/Music, deleted the Music directory in my home directory, and replaced it with a symbolic link (note: run from my user's home directory):

$ ln -s /media/share/Music Music

I started Rhythmbox and it worked as if nothing had changed.

Rebooting into Scientific Linux, I added the same line to /etc/fstab and ran the same mkdir and mount commands, then removed my still empty Music directory, made the same sym link, and voila, I had access to all my music from Scientific Linux (after installing Rhythmbox, that is).

For VirtualBox VM sharing, things are a bit more complicated.  Ubuntu makes installing VirtualBox trivial, since it is in the main repository, but on Ubuntu 14.04 version 4.3 is what you get.  On Scientific Linux I installed version 5.0 using the instruction from an earlier post.

Fearing there might be meta-data conflicts between the two versions, but feeling confident the virtual hard disk image files (.vdi) could be shared between them without conflict (since I regularly copy these files back and forth between distros without problems), I did the following:

1. On the Ubuntu side, I moved my entire VirtualBox VMs directory from my home directory to /media/share and sym linked to it as I had done with the Music directory.
2. On the Scientific Linux side, I kept VirtualBox VMs in my home directory, using sym links only for the virtual disk image files.  For example, from inside $HOME/VirtualBox VMs/Server1 I ran:
   

   $ ln -s /media/share/VirtualBox\ VMs/Server1/Server1.vdi Server1.vdi

This worked nicely.  Just for fun, I ran yum update on Server1 launched from VirtualBox 5.0 on Scientific Linux, then rebooted into Ubuntu 14.04 and relaunched Server1 from there, seeing changes I had made.

Finally, after noticing that VirtualBox-4.3 was available for Scientific Linux 7.1, I ran # yum remove VirtualBox-5.0 and then # yum install VirtualBox-4.3, made the VirtualBox VMs directory in my home directory a sym link to /media/share/VirtualBox VMs and quickly added all the VMs back.  Now even the VMs with the VirtualBox extensions installed (for full screen GUI and auto mouse capture) work on both OS's.

Thonny - A Python IDE for Beginners

I received an email a few days back from Aivar Annamaa about a Python IDE for beginners called Thonny.

The YouTube video introducing the IDE looks promising, so I am jumping at the opportunity to take a look at it.

Thonny is in the Python Package Index, so it can be easily installed (and installed by user without system admin privileges) using pip.  In a previous post I documented installing Python 3.4, which is required to before what follows.

First I want to get pip3.  Since it is not yet in the main Centos repository, I installed it with (note: run $ sudo -i and then # exit before running this command in the same terminal emulator so as not to be prompted for a sudo password):

$ curl https://bootstrap.pypa.io/get-pip.py | sudo python3.4

I want to install Thonny inside the user's local directory, so I installed it with:

$ pip3 install --user thonny

This installs the thonny egg in $HOME/.local/lib/python3.4/site-packages (creating the needed lib/python3.4/site-package directory if it is not already there), and installs a shell script to launch it in $HOME/.local/bin. When I tried running thonny from the command prompt, I got an error message: ImportError: No module named 'tkinter'. So I needed to install tkinter:

$ sudo yum install python34-tkinter

after which thonny launched.  It complained that it couldn't find rope or jedi, however, so I installed those locally as well:

$ pip3 install --user rope
$ pip3 install --user jedi

Since thonny is a GUI IDE, I wanted a GUI launcher for it.  To get one I created a Thonny.desktop file based on the one I found here, with the following contents:

[Desktop Entry]
Type=Application
Name=Thonny
GenericName=Python IDE
Exec=/home/[username]/.local/bin/thonny %F
Comment=Python IDE for beginners
Icon=/home/[username]/.local/lib/python3.4/site-packages/thonny/res/thonny.ico
Terminal=false
Categories=Application;Education;Development;Debugger;IDE;
MimeType=text/x-python;
Actions=Edit;

[Desktop Action Edit]
Exec=/home/[username]/.local/bin/thonny %F
Name=Edit with Thonny

and placed it in my /home/[username]/.local/applications directory (Note: replace [username] with your actual username).

Here is a screenshot of Thonny running hello.py:

My next task will be to go through some beginner Python lessons using Thonny to see how it feels.

Resizing a Logical Volume on Centos 7.2 with system-storage-manager

My desktop machine at work was setup to dual-boot Ubuntu 14.04 and Windows 10.  Deciding I needed Centos 7.2 much more than Windows 10, I installed Centos into the space that had been occupied by Windows.

Using the Centos 7 installation DVD, I followed the partitioning proceedure that I can now almost do in my sleep, creating the following partitions:

1. 500 MiB /boot with an xfs file system on an actual partition
2. 1024 MiB swap
3. 20 GiB / with an xfs file system on a logical volume
4. /home with whatever space is left with an ext4 file system on a logical volume

I said I could almost do this in my sleep. I made one huge mistake.  Instead of making the /home partition with GiB, I made it with MiB!  I didn't notice this until I got a warning about the home partition running out of space.  I had spent a lot of time already installing and then updating the system.  I didn't want to go through that again.

So I used this mistake as an opportunity to explore resizing my logical volume.  It took a bit of poking around, but eventually I found this webpage, from which I did the following:

1. Logged into the GUI as root so that /home would not be in use.
2. Ran yum install system-storage-manager to install ssm.
3. Ran ssm list to see my volumes.
4. Ran ssm resize -s [size] [volume] to make /home larger.

It worked like a charm, and now I'm logged back in with my regular user with a few hundered gigabytes of space in my /home partition.

Setting Up a Home Centos 7 Server

I have a little Zotac Zbox server at home that I've been running for several years with Ubuntu server.  It has a 500 GiB hard drive, 2 Gigs of RAM, and a dual-core 1.8 GHz Atom processor.  It is small, quiet (silent, actually) and sits unobtrusively on a shelf. It is truly a wonderful little device, and I've made good use of it for learning server administration in a safe and inexpensive way. DynDNS provides me with a domain name that I can use to access it from the outside world since it is sitting at home on my Comcast connection.

Since I am preparing for the RHCSA this Spring, I figured I should install Centos 7 on it. To do the install, I needed to connect it to a monitor, keyboard, and mouse. I setup the following LVM partitions:

/boot 500 MiB xfs
swap 1 GiB
/ 20 GiB xfs
/var 197 GiB ext4
/home 241 GiB ext4

and did a minimal install, then ran:

# yum update
# yum install net-tools
# yum install vim

The next task was to configure it to have a static IP address, after which I could unplug it from the monitor, keyboard, and mouse and put it back on the shelf. To set a static IP address, I used this and this web pages as guides.  I ran:

# vi /etc/sysconfig/network-scripts/ifcfg-ens32

and changed:

TYPE="Ethernet"
BOOTPROTO="dhcp"
DEFROUTE="yes"
PEERDNS="yes"
PEERROUTES="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_PEERDNS="yes"
IPV6_PEERROUTES="yes"
IPV6_FAILURE_FATAL="no"
NAME="ens32"
UUID="aed7d424-7293-4db7-8a89-c25f77557bf9"
DEVICE="ens32"
ONBOOT="yes"

to:

TYPE="Ethernet"
BOOTPROTO="none"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
NAME="ens32"
UUID="aed7d424-7293-4db7-8a89-c25f77557bf9"
DEVICE="ens32"
ONBOOT="yes"
HWADDR="00:01:2e:bd:15:e3"
IPADDR="10.0.0.254"
PREFIX="24"
GATEWAY="10.0.0.1"
DNS="10.0.0.1"
IPV6_PEERDNS="yes"
IPV6_PEERROUTES="yes"

I tested that I could connect to the new server from outside, and it worked, but it actually took more than 2 minutes to connect.  I'll have to look into why that is.

 

Symlinking python3 to python3.4

Next I installed Python 3.4 (since what use is a computer without Python 3?) using the steps I described in my previous post.

To be able to type python3 instead of python3.4 to launch this version of Python, I made a symbolic link.  First I took a look at the .bash_profile file, which contained the following:

# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

# User specific environment and startup programs

PATH=$PATH:$HOME/.local/bin:$HOME/bin

export PATH

.local/bin is being added to the PATH, but I didn't yet have this directory, so I made it and then changed directories to it:

$ mkdir .local$ mkdir .local/bin
$ cd .local/bin

from here I ran:

$ which python3.4

to find out where it was located, and then made the symlink:

$ ln -s /usr/bin/python3.4 python3

after which I could launch Python 3 they way I wanted, as the following screenshot shows:

Installing Python 3.4 on Scientific Linux

I  do a lot with Python in my cs program, and as an active member of the python community, I heeded the BDFL's request years ago to make the switch to Python 3.

So it was a bit disconcerting to find that Python 3 was not installed on Centos 7.  Fortunately, after a few false starts, I found that it is now very easy to add it:

# sudo yum install epel-release
# sudo yum install python34

You need to start this with

# python3.4

rather than

# python3

No matter, this will provide a nice opportunity to talk about symlinks with my students (note: I document how to make this symbolic link in my next post).

I decided to install Scientific Linux on the last available machine in our lab, just so we can have a look at it.

Here it is with python 3.4 running:

From a first look it seems to very compatible with Centos 7 / RHEL.  Our textbook mentions that it would be OK to use it to prepare for the RHCSA.  Now we have a box running it to play with.

Installing VirtualBox on Centos 7

Last post I described how to install VirtualBox Guest Additions on Centos 7.  Since we are now running Centos 7 as the host operating system on several machines in our IT lab, we will also need to install VirtualBox itself on these machines, so that we can run VMs for testing that are hosted on the Centos boxes.

Here is how to do that (Note: be sure you are running the latest kernel before you start, and thanks to this post):

# cd /etc/yum.repos.d/
# wget http://download.virtualbox.org/virtualbox/rpm/rhel/virtualbox.repo
# yum install epel-release
# yum install dkms
# yum install VirtualBox-5.0

VirtualBox will now appear in the Applications -> System Tools menu.

Before individual users can create VMs, they have to be added to the vboxusers group with:

# usermod -a -G vboxusers [user name]

 Users added to the group can now start VirtualBox and install VMs.

Adding Virtualbox Guest Additions and Google Chrome to Centos 7

One effective strategy in preparing for the RHCSA certification is to spend as much time in a Centos environment as one can doing the kinds of things one does each day with a computer.  I'm not prepared yet to give up my Ubuntu desktop, but I've found VirtualBox to be a fine way to switch OSs with ease.

We will be using VirtualBox VMs extensively in our Linux System Administration course, and we have installed two by default, one with a Gnome GUI and one without a GUI.  I want to be able to run the VM with a GUI in full screen mode on my 2560 x 1600 resolution monitor instead of the 1024 x 768 resolution that runs in the VM by default.  I would also like to be able to switch mouse control in and out of the VM without having to press the right control key.  Both of these wishes are granted by the VirtualBox Guest Additions.

As this post explains, all you have to do to get your Centos 7.2 VM ready for Guest Additions is to run:

# yum install epel-release
# yum install dkms

After that, select:

Devices -> Insert Guest Additions CD image...

from the menu of the window containing your running VM, and click on the buttons to download and then mount the image.  After doing that, I changed to the directory where the CD image was mounted with:

# cd /run/media/user/VBOXADDITIONS-$.3.34_104062

and ran:

# ./VBoxLinuxAdditions.run

and then:

# shutdown -r now

After that, I had everything I wanted.  I can resize the window, or maximize it (with Right Control & F keys).  When not full screen, mouse control is transfered to the VM whenever the mouse pointer enters its window and back to the host OS whenever the mouse pointer leaves its window.

In fact, beginning with this sentence, I editing this blog entry from my full screen Centos 7.2 desktop:

Installing Chrome

Then next task to setup a fully functioning desktop is to install Google Chrome.  Here is how to do it:

1. Create a file /etc/yum.repos.d/google-chrome.repo with the following contents:
   

   [google-chrome]
   name=google-chrome
   baseurl=http://dl.google.com/linux/chrome/rpm/stable/$basearch
   enabled=1
   gpgcheck=1
   gpgkey=https://dl-ssl.google.com/linux/linux_signing_key.pub
   

2.  # yum install google-chrome-stable

That's all there is to it.  This has been another fine experience with Centos.  I'm liking it more and more each day ;-)

Chalk Up One for Centos: Removing Old Kernels

I have committed to memory the commands needed to remove old kernels from the Lubuntu 14.04 workstations in our lab:

# dpkg --purge linux-image-extra-[kernel version]-generic
# dpkg --purge linux-image-[kernel version]-generic
# dpkg --purge linux-headers-[kernel version]-generic
# dpkg --purge linux-headers-[kernel version]

With the frequency with which new kernel versions have been released, this can become a rather tedious process.  I have machines in the lab that have many old kernels, and this collection of 4 dpkg --purge commands has to be run for each old kernel on each machine.  I can hear the skilled sys admins out there groaning that I should just run ... (fill in the correct CLI command here - probably involving xargs or something), or set up proper configuration management using Puppet or something.

Despite my years and years teaching with GNU/Linux systems, however, I am not much of a sys admin, and I don't know how to nor do I feel confident enough to try commands like that.  I'll either end up deleting the current kernel, or spending half the day getting the command to work, and then fail to complete my teacher responsibilities (lesson planning, gradeing, etc.) as a result. In years past I've relied on bright, fast learning students to become the sys admins of our lab, but we are in a rebuilding process at present and I don't have any students with these skills at present.

I'm confident that preparing for the RHCSA certification this Spring will help me become better at this sort of thing, but I am philosophically committed to software freedom, and the idea that you have to be some sort of wizard to use free systems properly runs counter to idea that software freedom should be promoted as widely as possible.

It turns out that Centos 7 has a delightfully simple way to address the old kernel problem (see this for more information).  Just run:

# yum install yum-utils
# package-cleanup --oldkernels --count=1

I searched in vain for anything on the Ubuntu side this simple.  The best I could find was this post, which was not very comforting.

Chalk up a clear win for Centos on this one!

GUIs, CLIs and Updates on Centos 7

In addition to running Centos 7 in VirtualBox to prepare for the RHCSA exam, I am installing it on several machines in our IT lab at the Arlington Career Center, since the best way to become truly comfortable with an OS is to use it in day to day activity.  After many years (since 2004) using Ubuntu as my desktop OS, I feel very comfortable with its quirks and with navigating my way around Launchpad and Personal Package Archives (PPAs) and such to find and install the software I need.

Centos 7 is new to me, so it will take me awhile to reach that same feeling of comfort.  I had an early experience that is a bit disconcerting, which raises some questions I would like to get answered early on in the process.

Following the instructions in the text we are using to prepare for the RHCSA, I selected "Server with GUI" from the software selection dialog.  When the install finished, I had a Gnome Shell 3 desktop.  The following screenshot shows this desktop with the System Tools menu displayed:

 

I'm in the habit of running system updates obsessive compulsively (as I do most everything), so the first thing I did after completing the install was click on the "Software Update" menu to run updates.  The next screenshot shows the update process underway:

When it finished, I was caught by a surprise.  The menu options under "System Tools" had changed, and options "Software" and "Software Update" weren't there anymore:

I've been telling my young charges that "real sys admins don't use GUIs" since the beginning, so I would be perfectly comfortable if it were the case that the proper way to update Centos 7 is just to run:

# yum update

and that we should simply avoid the GUI update and package tools which have now disappeared anyway. I'll be more comfortable when I can read this as official Centos doctrine, so I'll be looking for statements to that effect as I continue learning.  I also need to find out how to work with RPM repositories, and which ones I should add to our lab workstations that will best provide software I will want without causing conflicts and breaking things.

To see if I could learn more about the disappearing menu items, I did a Google search on "Software Update" disappears from Centos 7 after running it and found this, which was helpful. It seems odd to me that such a big change would be made between what I would assume to be a minor release update (7 to 7.2), but getting a feel for how things work in Centos is what I am after, so this experience will be part of my education.

Starting the New Year with RHCSA Study

During the Spring semester, I will be working with four students in a dual-enrolled (high school and college credit) course titled: ITN 170: Linux System Administration. While learning to administer GNU/Linux systems, we will also be preparing for the RedHat Certified System Administrator (RHCSA) exam.

I will document our progress here, and ask that the four students keep blogs of their own.

I first used RedHat software in 1995 with the original RHL 1.0 release in May of that year.  I had been using Slackware prior to that, and RedHat quickly became my distro of choice.  It remained so until the first release of Ubuntu in 2004. So this will be something of a return to my past, and I'm looking forward to seeing how much of what I remember still holds.

As a first task, I wanted to find out how to easily remove old kernels from the Fedora 23 box we setup in the lab.  A quick search revealed this. It couldn't be much simpler:

• # dnf install yum-utils
• # package-cleanup --oldkernels --count=1

My next task was to install VirtualBox.  This is a single command on Ubuntu, but is a bit more complicated on Fedora.  Not too bad, however, with the documentation here.  I used the following four step process:

•  # cd /etc/yum.repos.d/
•  # wget http://download.virtualbox.org/virtualbox/rpm/fedora/virtualbox.repo
• # dnf update
• # dnf install binutils gcc make patch libgomp glibc-headers glibc-devel kernel-headers kernel-devel dkms

So 2016 will be the year I return to my RedHat roots.  Happy New Year!