Linux User Group of Mauritius Promoting open source software in our beautiful island

6Oct/170

How to reduce the amount of disk space used by the systemd journal

Posted by Avinash Meetoo

We, Linux people, generally use systemd now and one of its components is the journal controlled by the journalctl command line tool.

As explained on the Arch wiki,

systemd has its own logging system called the journal. The /var/log/journal/directory is a part of the systemd package and the journal will write to /var/log/journal/

The journal is always appended and therefore grows in size. On my laptop, the journal was taking 1.8Gb of space and was full of details which, I believe, I’ll never need. So I decided to clear all old contents (which the systemd people call a vacuum). I issued:

journalctl --disk-usage
journalctl --vacuum-size=64M
journalctl --disk-usage

And the journal immediately became smaller. I then issued a

journalctl --verify

which made ma realise that some of the remaining journal files were corrupted (for some reason). There is no journal repair tool in systemd so I simply removed the offending files (with rm).

Now, I can easily check my journal entries for today and I know everything will be all fine:

journalctl --since today

8Aug/170

Ghost Desktop on Xubuntu 17.04 won’t start

Posted by Jochen Kirstaetter

Ghost Desktop on Xubuntu 17.04 won't start

Already before the migration from Joomla to Ghost last weekend I run the Ghost Desktop application on Windows. Now, after the successful completion it was about time to get going on my other machines. You know, the ones away from the main rig... Usually used during the evening hours, just for fun, or experimenting.

Tonight, I decided to give one of my Linux systems some attention, started to upgrade some packages, and installed new software. Among those also Ghost Desktop App for Linux. On the Ghost website you get version 1.3.0 (as of writing), and it's a Debian package.

Knowing that the desktop app is an Electron-based application, and I already packaged a few Electron apps myself, it would run on any Ubuntu-based system, too.
Note: This post was written in Ghost Desktop running on Xubuntu 17.04 64bit

Installation of Ghost Desktop

Either you double-click on the downloaded .deb package and your system will prompt you to open/install the application in Software, or you can run the following command in the Terminal:

$ sudo dpkg -i ~/Downloads/ghost-desktop-1.3.0-debian.deb 

Ghost Desktop can then be launched via the Application Menu/Launcher under ghost-desktop or if you prefer the terminal:

$ Ghost

The problem: Ghost Desktop won't start

If you try to launch the application via the menu or any other GUI launcher you won't get any response at all. The software just isn't executed, it seems.

Compared to running it in the Terminal. This might produce the following output:

$ Ghost
A JavaScript error occurred in the main process
Uncaught Exception:
Error: Unable to find a valid app
    at Object.<anonymous> (/usr/lib/Ghost/resources/electron.asar/browser/init.js:121:9)
    at Object.<anonymous> (/usr/lib/Ghost/resources/electron.asar/browser/init.js:173:3)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.runMain (module.js:605:10)
    at run (bootstrap_node.js:424:7)
    at startup (bootstrap_node.js:147:9)

The solution: Set permissions

Fortunately, this has been reported already on GitHub by user letsjustfixit. The issue is caused by a missing permission bit on the Electron app. A temporary workaround has been documented until the package is going to be fixed.

Run the following chmod to set read and execute bits on the Electron app and dependent components. Then launch Ghost Desktop again.

$ sudo chmod -R +rx /usr/lib/Ghost/resources/app
$ Ghost 

 ⚡️  Welcome to Ghost  👻

Happy blogging!

It's great to see that such issues are handled on GitHub, and the "fix" is easily done.

As maintainer of own Electron-based applications I'm interested in the root cause. So far, I didn't come across a similar problem (touching wood!). Thankfully, I'm going to add this to my notes on Electron.

If you're familiar with this kind of problem regarding Electron packaging on Linux, give it try to fix it. On my side, I already cloned the Ghost-Desktop repository. Let's see whether I'm able to create a pull request for the Ghost community.

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15Mar/170

Open and not extract .docx, .xlsx and .pptx files in the latest Gnome 3

Posted by Avinash Meetoo

In the latest version of Gnome 3, a subtle change was brought to Nautilus, the file manager, to automatically extract the content of a ZIP file in a new folder when it is double-clicked on instead of open an application to do so. The problem is that Microsoft Office files (.docx, .xlsx, .pptx, etc.) are ZIP files. This means that double-clicking on a .pptx file extracts its content instead of opening the file in, say, LibreOffice Impress!

This makes life miserable for all those who need to open Microsoft Office files on a regular basis and, of course, this is a bug (as acknowledged by the Gnome people  and the Red Hat / Fedora people).

Fortunately, it is quite easy to make Nautilus become sane again. Open Preferences and in the Behavior tab, unselect “Extract the files on open” in the Compressed Files section.

Phew!

15Jun/160

Automatically raise windows in Gnome

Posted by Avinash Meetoo

20160615-automatically-raise-windows

I love Gnome 3… except when I am using a terminal, decide to launch Chrome by clicking on its icon in the Dash and not realising that the terminal still have focus despite Chrome being shown on screen. Consequently, typing, say, www.noulakaz.net and pressing enter only sends these keystrokes to the terminal (despite Chrome being shown) with potentially serious consequences.

But lo and behold, I have just found a solution. Just launch the Gnome Tweak Tool as shown above and put “Automatically Raise Windows” to ON.

I have regained my sanity!

1Jun/160

Vagrant box export and import

Posted by Ish

I’ve been a VirtualBox user for a few years but I started working with Vagrant only recently. Vagrant provides an easy-to-use portable environment on top of virtual machine providers like VirtualBox, VMware, AWS etc; at least that is what is written everywhere.

While the internet abounds with articles and «expert» answers about how to work with Vagrant, I stumble upon a lot of blurry advice in needy times. The last resort, though not very tempting, is the official documentation. I say not very tempting because of the amount of reading required for just one set of command options.

Vagrant box export and import

Hashicorp, the company that funds the full-time development of Vagrant, hosts a catalog of Vagrant boxes for the different virtual machine providers, which is called Atlas. Let’s look at the command that is used to add a box to Vagrant.

vagrant box add opensuse/openSUSE-42.1-x86_64

In the above command opensuse is a user of Atlas and openSUSE-42.1-x86_64 is the name of the box. You might need the --provider option if you’re not using VirtualBox. Once the box has been added, it can be initialized as follows:

vagrant init opensuse/opensuse-42.1-x86_64

The command creates a Vagrantfile in the current directory with a lot of commented lines which you can uncomment to specify needed options with your Vagrant box (e.g shared folders, set memory etc). The following line in the file tells vagrant which base to use when provisioning the virtual machine the first time:

config.vm.box = "opensuse/opensuse-42.1-x86_64"

To start up the Vagrant box we’ll do vagrant up and a bunch of messages depending on the Vagrantfile parameters will show up (e.g SSH port forwarding). Next we do vagrant ssh to jump inside the Vagrant box. The first time the Vagrant box is started, a virtual machine is provisioned in VirtualBox (since that is what I am using as provider). At next boot the VM will jump to normal startup unless «provisioning» options are specified.

As Vagrant users enjoy easy portability of the boxes, the same can be exported following this quick procedure:

vagrant package --output opensuse-devel.box

Say you have set up a development environment on the openSUSE box and you need to share the same with other developers. The above command packages the virtual machine in one file, in our case it’s called opensuse-devel.box. Next each developer needs to add the box as follows:

vagrant box add openSUSE-devel opensuse-devel.box

I am naming the project openSUSE-devel for easy reference.

Sure, if not executed from the directory containing opensuse-devel.box then the full path to the file should be used. It makes the box available to Vagrant and a machine can then be initialized.

vagrant init openSUSE-devel; vagrant up

This creates the Vagrantfile and fires up the box. When one needs to destroy the box, just execute vagrant destroy and the virtual machine will be gone.

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23May/160

Developers Conference 2016, day 3 with openSUSE bug hunting

Posted by Ish

I had my «openSUSE bug hunting» presentation scheduled at 09h30 this morning. I’m usually very lazy on Sundays but the enthusiasm of the Developers Conference is just an amazing feeling. Though we live on a small island, we get to meet some people maybe just once a year during this fun event. I picked up Shelly on the way and we reached Voilà Hotel at 09h05. Right at the hotel entrance Yash was waiting, he might have seen us coming. We went upstairs chatting and met JoKi. My presentation was scheduled at the Accelerator and I thought I’d just go and test the gear. Aargh! The TV had only HDMI cable and my ThinkPad had VGA & a Mini DisplayPort. That said, I needed an adapter. Joffrey who came around greeting everyone had a HDMI to VGA cable, which he lent me. At that same time JoKi also came with a Mini DisplayPort to HDMI convertor. Great! Then I had an adapter plus a backup.

I mirrored my laptop display and checked if everything’s fine. All good and it was 09h30.

Developers Conference 2016, openSUSE bug hunting

Thank you for the photo, Shelly :)

However, folks were still coming, so we thought let’s just wait till 09h45 giving a chance for others to arrive. Indeed I started at 09h45 sharp with a 3/4 full room and just a few minutes later it was «house full». That was great and a true encouragement though a Sunday morning.







Thank you for the (re-)tweets folks. :D

I chose the title of my prez «openSUSE bug hunting» from a blog post I wrote in 2013 while running «release candidates» of openSUSE. Starting the presentation I spoke about how some folks might organize special events working to hunt and find bugs, while some bugs we just encounter when doing regular tasks. What do we do when we find one of those bugs? Do we just ignore and think, «it’s just an error, nothing more», and we continue work? Do we search on the internet whether others encountered similar errors and if there is a fix? Few people ever consider filing a bug report through the right channel, unless it’s just a «button» away like some applications (e.g web browsers) offer.

Bug reporting most of the time require some information gathering from the system; that is where I took the presentation. Before diving further into the system though, I opened a few bug reports from openSUSE Bugzilla to show as example. I also gave a quick overview of the openSUSE Build Service and openSUSE Connect. That helped show the audience how to find package maintainers and get information about official and non-official packages.

I did not have slides; but I rather fired-up an openSUSE Vagrant box inside which I had setup an environment for demos. The rest of the «talking» happened within the Vagrant box. We looked at how to obtain system information using command-line utilities and from the /proc fs. Next we looked at digging for application error info in log files. We played with systemctl and journalctl which gave us clear and concise information about application states. We then queried using rpm and its various options to get as much information about packages that we can use when filing the bug report. At that time an openSUSE user from the audience said we can also use zypper to search for installed packages on the system. Yes, indeed, but rpm -qa | grep php shows no clutter compared to zypper se php. I however grabbed the opportunity to tell the audience that folks having a «debian lifestyle» can still type aptitude equivalents to search and install packages from the command-line; thanks to the «zypper-aptitude» compatibility scripts written by Bernhard M. Wiedemann.

All while we continued digging for application errors and how to search and sort things from the logs; I did a quick demo using Nginx and PHP-FPM.


We talked about the need of default configuration files after installing PHP 7 and that such changes need to be addressed with the «openSUSE factory» guys.

It was near 10h30 and Jeshan signaled me that the next speaker had already come. I asked for a last 5 mins to show something quick using the «strace» tool. Actually a university student asked me a question before the event and I invited him to come to the prez and ask the question again so we could altogether see how tracing tools can help us find useful information for bug reports. That part of the prez might be good for a separate blog post. I sincerely have to apologize to the next speaker if he is reading this post; we started 15 mins late and that surely must have impacted other presentations.

Eddy and I talked about work stuffs after the presentation. Then some of us went to Bagatelle food-court for a mini-break. When we came back Sun was preparing his gear for the next presentation. He talked about grid systems, explained what are decks & cards and how it’s used on lexpress.mu. He showed some hidden features of lexpress.mu, like what happens when you type «heart» or «superlsl» while you’re on the homepage and how the text is read if you type «kozer» while you’re on an article page.


Sun demoed the «live article» feature of lexpress.mu and the work needed behind to keep it light, simple and fast. He talked about «facebook instant articles» and definitely we’re proud to be the first media group, not just in Mauritius, but in the African continent to deploy the same.


After Sun’s presentation I met my ex-colleagues and we went for a pizza & beer lunch at Flying Dodo.


The pizza being late and as the Developers Conference closing ceremony had started Shelly, Ubeid and I rushed back.

JoKi’s wife, Mary Jane, Vincent, Louis, Arnaud and a few others, we had figured how to hijack JoKi’s speech and bring on some more party time to celebrate JoKi’s birthday. Yeah, he’s getting old, now it’s confirmed as he turns 40. Ubeid quickly edited some slides and we told JoKi that as he finished his speech thanking everyone, we had a quick stuff to show; some sort of observation we’ve made. Ahaan! That’s when Arnaud, helped by Mary Jane’s cousin, they brought that big cake along with its table.

Everybody cheered! Everybody laughed. We all had fun, we had cake, we took crazy photos and celebrated the end of Developers Conference 2016.

Developers Conference 2016

Developers Conference 2016

Developers Conference 2016

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21May/160

DevConMru 2016, day 2 – Linux Installfest

Posted by Ish

It was Saturday morning and I found myself rushing to be at Flying Dodo just in time. Oh, to be precise «not in time» but like 15 mins later than I expected to be, that 09h45. The night before I got busy preparing the box of openSUSE goodies, sorted the stickers, pamphlets, DVDs and cheat sheets. Little I knew that folks would like those so much. I would tweet as I got the pack ready.





Shelly and I were the first geeks to reach Flying Dodo. While I would setup my laptop with the projector, she prepared the tables with the stickers and cheat sheets.

Developers Conference, Linux Installfest

The first few geeks came shortly afterwards. Ronny and Ajay from the Linux User Group of Mauritius came along with their gear. Oh, this little gang from the University of Mauritius hopped in and yes we were under attack. We also received the visit of folks from the PHP Mauritius User Group.



The morning session was great. Ajay, Pritvi, Ronny and Avish helped people getting their laptop Tux’ed either with Ubuntu or with openSUSE. Meanwhile I got to run an interactive session with the university folks with a command-line walk-through.


There was a question about email headers. I showed email headers from my Gmail account and also from Thunderbird. We talked a little bit about IETF RFC 2822 and together we looked at some of those colon-separated field values. Ajay gave us a simple yet clear explanation on SPF and DKIM. We did a ‘dig’ on a couple few domains to read the TXT records. Ajay explained about hard-fail and soft-fail in the SPF records and how they affect delivery of email.


I tried answering other questions that popped up; covering various topics like SSH, file permissions, etc, and we had real fun during that interactive session.


Jeshan joined us later after his AWS Lambda presentation at Voilà Hotel and offered a little support to Ashmita who tried installing openSUSE (dual boot) on her laptop. Mission was successful! It was great to meet Bernard who got an Ubuntu dual-boot on his laptop and Nirvan Mahadooa who wanted to meet the Linux geeks. I really hope we can continue the geek chat at a later time folks.


Some of us stayed till dinner-time at Flying Dodo sharing «samousa», pizza and beer. Oh, Shelly and I had non-alcoholic drinks. :D

Developers Conference day 2

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22Mar/160

Customizing the GNOME Shell

Posted by Ish

A couple of weeks back I was customizing the GNOME Shell on my openSUSE Tumbleweed laptop by tinkering with the CSS files of the desktop theme. A colleague of mine who peeked onto my screen at that moment, as he needed to show me something, nudged at the ugly rounded-corner buttons he saw on the taskbar. To be precise that was the “window list” that he saw, an extension that can be installed from gnome.org.

I told him it only requires editing the Cascading Style Sheet (CSS) of the extension, which could be found at /usr/share/gnome-shell/extensions/window-list@gnome-shell-extensions.gcampax.github.com, to adapt it to the desktop theme and make it more appealing. In fact, it did not take long to realize that removing the border-radius and the box-shadow actually blended the button better with the theme.

GNOME 3 - GNOME Shell, window list

.window-button > StWidget {
  -st-natural-width: 18.75em;
  max-width: 18.75em;
  color: #bbb;
  background-color: #393f3f;
  /* border-radius: 1px; */
  padding: 3px 6px 1px;
  /* box-shadow: inset 1px 1px 4px rgba(255,255,255,0.5); */
  text-shadow: 1px 1px 4px rgba(0,0,0,0.8);
}

He then pointed to title bar of the Firefox window and said “see, this thickness of the title bar makes it waste space.”

I looked at the window and replied “yeah, indeed but those should be configurable in some CSS file lying around.”

I then got back to work. Today, however, I looked at the title bar again and thought of reducing it’s size. A few hacks have been proposed by people who wished to achieve the same. The best proposal I saw was configuring through the gtk.css file rather than editing the individual theme files. If you do not find the gtk.css file, then create one ~/.config/gtk-3.0/gtk.css.

.header-bar.default-decoration {
    padding-top: 3px;
    padding-bottom: 3px;
}

.header-bar.default-decoration .button.titlebutton {
    padding-top: 2px;
    padding-bottom: 2px;
}

Adjust the padding value to get the desired result. The above gave me a slimmer title bar that would not waste space as before.

GNOME 3, GNOME Shell, window title bar

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20Mar/160

Build a personal wiki using Vim

Posted by Ish

I used to have random notes in text files scattered on the disk. Then I tried being an organized person by using things like Google Docs… but, after some time I would find myself coming back to the simple text editor when in need of quick notes. On my openSUSE laptop I would either fire up Gedit or if the terminal is already open I’d use Vim.

A few days ago while searching for some packages in the openSUSE repo, I came across the vim-plugin-vimwiki package for Vim. It turned out to be a handy plugin for the Vim text editor.

sudo zypper in vim-plugin-vimwiki

At next launch of Vim, type ww and press “enter” to start the wiki.

gVim text editor

Screenshot of gVim

A folder named “vimwiki” will be created in the home directory of the user. For example for the user “ish”, the following message will appear upon typing ww:

Vimwiki: Make new directory: /home/ish/vimwiki
 [Y]es/[n]o?

A first blank file named “index.wiki” will be created in the “vimwiki” directory. The wiki has support for links, which are created using double brackets, e.g [[Hello Wiki]]. The text between the brackets become click-able and the file “~/vimwiki/Hello Wiki.wiki” is created.

Vim Wiki links

One can navigate through the pages by pressing “enter” while the cursor is on the “link text” and using the backspace button to go to the previous page.

What about existing text files?

The existing text files can be renamed with a .wiki extension and moved to the vimwiki directory. Then use the double brackets to link to that file.

I find the Vim Wiki being a simple & effective solution to take quick (re-usable) notes in an organized manner. Surely other solutions exist but at the moment I’d stick to Vim Wiki.

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24Dec/150

Find user IP address with Cloudflare & Nginx

Posted by Ish

A content delivery network (CDN) is a distributed network of servers that delivers content, typically webpages, to users based on their geographic location. A CDN would serve you from a less distant location on the network.

CloudFlare provides such a CDN service. A friend recommended me to use CloudFlare around a year or so, and I do not regret accepting.

Find user IP address with Cloudflare & Nginx

CloudFlare Global Network, Source: cloudflare.com

I noticed considerable performance gain when I switched to CloudFlare.

PING hacklog.mu (104.28.11.229) 56(84) bytes of data.
64 bytes from 104.28.11.229: icmp_seq=1 ttl=51 time=114 ms
64 bytes from 104.28.11.229: icmp_seq=2 ttl=51 time=115 ms
64 bytes from 104.28.11.229: icmp_seq=3 ttl=51 time=113 ms
64 bytes from 104.28.11.229: icmp_seq=4 ttl=51 time=113 ms
64 bytes from 104.28.11.229: icmp_seq=5 ttl=51 time=114 ms

--- hacklog.mu ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4004ms
rtt min/avg/max/mdev = 113.856/114.509/115.854/0.847 ms

CloudFlare bundles other features, among which the Firewall allows you to set rules for rogue visitors.

Get the user’s IP address with Nginx

CloudFlare proxies requests to your webserver and as such, your webserver log would record CloudFlare’s IP addresses. In order to obtain the user’s IP address in a request, you would need to activate the True-Client-IP Header from CloudFlare’s administration panel. However, that requires an Enterprise plan. It is not available in the free service.

There is one workaround using the ngx_http_realip_module in Nginx. It allows a change of the client address to one that is specified in the header field. CloudFlare specifies the same in the CF-Connecting-IP field. The technical story can be summed up as follows in the http context of Nginx:

http {

    set_real_ip_from 103.21.244.0/22;
    set_real_ip_from 103.22.200.0/22;
    set_real_ip_from 103.31.4.0/22;
    set_real_ip_from 104.16.0.0/12;
    set_real_ip_from 108.162.192.0/18;
    set_real_ip_from 141.101.64.0/18;
    set_real_ip_from 162.158.0.0/15;
    set_real_ip_from 172.64.0.0/13;
    set_real_ip_from 173.245.48.0/20;
    set_real_ip_from 188.114.96.0/20;
    set_real_ip_from 190.93.240.0/20;
    set_real_ip_from 197.234.240.0/22;
    set_real_ip_from 198.41.128.0/17;
    set_real_ip_from 199.27.128.0/21;
    real_ip_header   CF-Connecting-IP;

    ...
}

The IP addresses specified are those of CloudFlare and they can be obtained here. I suggest checking the page from time to time for updates or you might even monitor changes on the page (^^,) …


Ubuntu & openSUSE come bundled with ngx_http_realip_module. If Nginx is complaining about an unknown directive in your distribution, then you most likely need to compile Nginx with the --with-http_realip_module parameter.

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