## Exploring the newer GUI front-end, for use with SageMath.

One of the subjects which I had written about only yesterday, is that the Computer Algebra / Numerical Tool System called ‘SageMath‘ was available in the repositories, for Debian / Stretch – which is in itself news – and that additionally, the default way to use it under Debian is through a Web-interface called ‘SageNB’. Well what I’ve now learned is that the SageMath developers no longer support SageNB, and are continuing their work with the graphical front-end called ‘Jupyter‘.

But, installing Jupyter under Debian is a bit of a chore, because unlike how it is with custom-compiles, Debian package maintainers tend to break major software down into little bits and pieces. At one point, I had Jupyter running, but with no awareness of the existence of SageMath. What finally did the trick for me today, was to install the following packages:

• python-notebook
• jupyter-nbextension-jupyter-js-widgets
• sage-math-jupyter

Needless to say, that last package out of the three is the most important, and may even pull in enough of the other packages, to be selected by itself. It’s just that I did not know immediately, to install that last package.

So this is what SageMath 7.4 looks like, through Jupyter:

(Corrected 09/18/2018, 3h50 … )

(Updated 09/18/2018, 5h40 … )

(As of 09/16/2018, 20h10 : )

Frankly, I was a bit disappointed at first. My main disappointment seemed to be with the fact, that this GUI did not offer to typeset the Math. It does allow us to ‘download’ our Notebooks as PDF-Files, but when we do, we simply get the same, highlighted text, and graphics, only as a PDF – in code – or with whatever appearance the browser-view is already showing us. Also, the support for 3D plots is lackluster, as the plot above is non-interactive. At least with SageNB, I was able to select the ‘canvas3d’ viewer, which allowed the plot to be rotated. Also, if we use SageMath from the command-line, it defaults to using ‘JMol’ as its viewer, which is full-featured.

But as it turns out, I have discovered ‘the trick’, to getting Jupyter to typeset the users’ Math…

## File-Sharing under Linux, using Usershares – the Modernistic Way.

One concept which readers may already know, is that under Linux, we can set up a Samba-server, which makes the sharing-out of our home directories possible, and that if we fiddle with the ‘smb.conf’ configuration file thoroughly enough, it becomes possible to browse the available shares on a LAN, in a way semi-compatible with Windows computers that also reside on the same LAN.

Traditionally, this has always been a bit of a PITA, especially since the ‘/etc/samba/smb.conf’ configuration files have been finicky, and since each share practically needs to be configured individually, by a person with the ‘root’ password.

Well an alternative exists under Linux as well, which is the concept of ‘Usershares’. With this concept, each user who belongs to a specific group has the privilege, of designating a folder within his desktop manager, to share out, pointing-and-clicking. This is closer in ease-of-use, to how the process works under Windows. But, it needs to be set up correctly once, by the sysadmin, before it will work as often as simple users wish it to work.

I think that an existing Web-article on the subject, already explains well, what the settings in the ‘smb.conf’ file need to be, as well as what directories need to exist, in order for usershares to work. Except that the article I just linked to, refers to Fedora and SELinux systems and their norms. I happen to be based on Debian and KDE 4 or Plasma 5. And so I have a few observations to add:

Firstly, the following packages should be installed, under Debian also:


#apt-get install kdenetwork samba



Secondly, ‘/etc/samba/smb.conf’ needs to be edited like so:

Under Debian, the directory ‘/var/lib/samba/usershares’ already exists, If the relevant packages are installed. And its permission-bits have already been set as they should be set. Only, the feature is not configured in ‘smb.conf’ by default. And, the additional package named ‘kdenetwork-filesharing’ needs to be installed, in order for the tab to appear in Dolphin’s File-Properties box, that enables sharing from the GUI. Aside from that, enabled users need to be added to the ‘sambashare’ group, after which this membership only goes into effect, once the user in question has started a new session…

(Info Corrected 03/25/2018, 17h10,

Updated again 03/28/2018 … )

## Why visual SAMBA Browsing no longer works On My LAN.

One of the routine tasks which I recently carried out on my LAN, was to retire an old computer named ‘Walnut’. A day later I discovered that I could no longer browse my LAN, by way of my SAMBA shares. BTW, all my computers are by now either Debian / Jessie or Debian / Stretch computers. So what gives with the sudden inability to browse my shares via the GUI, which is the ‘Dolphin file browser’?

(Solved as of 03/23/2018 … )

Well in my ‘/etc/samba/smb.conf’ file, I gave the option:


[global]

(...)

smb encrypt = desired



The purpose of this was, for the Samba Server to query the Client, whether the  client supports encryption, and if affirmative, to enforce such encryption.

And, just to be sure that I haven’t made some silly mistake, I can run the following tests:


root@Phoenix:/etc/samba# cat smb.conf | grep "map to guest"
map to guest = Bad User
root@Phoenix:/etc/samba# cat smb.conf | grep "obey pam"
obey pam restrictions = no
root@Phoenix:/etc/samba#



But the disposition of the client to offer encryption, needed to be decided on the client machines, by creating a user-space file, i.e. a file in the home folder, which is named ‘~/.smb/smb.conf’, which contains the following lines:


[global]
client max protocol = SMB3



This is actually required, in order for the Dolphin / GUI-client even to offer the level of security which I wanted, which is SMB3 security. Without my specifying this, Dolphin would indicate to the Server, that SMB3 is not available, and no encryption would take place. This line of code can also be put into ‘/etc/samba/smb.conf’ , but I chose to put it into my home-folder like that.

## How To Install Yafaray Under Linux

One of the computing subtopics I dabble in, is the acquisition of 3D-graphics software. Therefore, I already have “Blender 2.78a”, which has its own built-in software-rendering engine, and I have several other rendering engines installed on my Linux-based computers.

Further, the rendering engines by themselves can be useless, unless they integrate well with a GUI (such as with Blender). And so one undertaking which I’ll typically reach with a given computer, is to install “Yafaray”, which used to be ‘Yafray’, which stood for ‘Yet Another Free Ray-Tracer’. If it’s installed properly, Blender can render its scenes, using Yafaray, but from within Blender.

Yafray used to be a much simpler piece of software to install than it has become. But I’m sure the effort I put into it this evening, will be well-worth it eventually. What I’m used to doing is to download a source-tree, and if it’s CMake-based, to run ‘cmake-gui‘ on it, to custom-pick my build options, and to go. But as it happens with Yafaray, this approach led to near chaos. What this did, was to compile all the source-code properly into libraries, but then to install those libraries to nonsensical locations within my system folders. One reason was the fact that a part of the project was to create Python 3 bindings, and another was the need for the Blender-integration, where modern Blender versions are based on Python 3. In any case I was sure to install all the build dependencies via my package-manager, but doing so was not enough to obtain working outcomes.