Linux on Thomas Schwery

My Git workflow

thomas@inf3.ch (Thomas Schwery) — Sat, 17 Aug 2019 16:00:00 +0000

Git is currently the most popular Version Control System and probably needs no introduction. I have been using it for some years now, both for work and for personal projects.

Before that, I used Subversion for nearly 10 years and was more or less happy with it. More or less because it required to be online to do more or less anything : Commit needs to be online, logs needs to be online, checking out an older revision needs to be online, …

OpenGL in a virtual machine

thomas@inf3.ch (Thomas Schwery) — Wed, 12 Jun 2019 18:30:00 +0000

As I prefer to work on a Linux computer for programming, at work I have to use a virtual machine to execute the product and test in a real environment using different Windows versions.

The problem encountered is that the emulated graphics card, even with full drivers in my KVM setup is only providing an OpenGL 1.1 version, something so old that some of the functionalities of our application are not working and display black boxes instead.

Subversion migration to Git

thomas@inf3.ch (Thomas Schwery) — Fri, 12 May 2017 18:30:00 +0000

Some time ago I was tasked with migrating our Subversion repositories to Git. This article was only written recently because, well, I had forgotten about the notes I had taken during the migration and only stumbled on them recently.

Our largest repository was something like 500Go and contained a little more than 50'000 commits. The goal was to recover the svn history into git, keep a much information as possible about the commits and the links between them, keep the branches. During the history, there were a number of periodic database dumps that were committed that now weighted down the repository without serving any purpose. There were also a number of branches that were never used and contained nothing of interest.

Network Debian Install

thomas@inf3.ch (Thomas Schwery) — Sun, 12 Mar 2017 22:00:00 +0000

This is a follow-up of the previous Preseeded Debian Install article, this time to add the capability of asking for a headless install through SSH.

I received every part of my future storage server and needed to install Debian on it. As I did not want to hook up a keyboard and display on it just to install the OS, I looked into the Debian Installer Network Console.

The concept is really simple, as always: The installer can be seeded through the first parts of the installation until the network is available and then let the user continue through SSH.

Preseeded Debian Install

thomas@inf3.ch (Thomas Schwery) — Sat, 25 Feb 2017 22:00:00 +0000

Since I tend to reinstall my laptop quite often -each time I have to use it for work more or less-, I wanted to automate a large portion of the installation process, from the installation itself to the configuration.

I delegated the configuration part to SaltStack, which I will cover in a future post, once I figured out everything I needed. This first part will cover the Debian installation, using the preseed mechanism that is available in the Debian Installer.

Debian Preseeded install medium

thomas@inf3.ch (Thomas Schwery) — Tue, 02 Aug 2016 09:00:00 +0000

After the configuration of my servers through Saltstack, I decided to go furter and to also store the configuration to my laptops and home computed into Saltstack and thus allow an easy way to format and get a fully configured system back in place really easily and quickly.

First step was to get a quick way of formatting my computers without or with only minimal human intervention. As I’m using Debian, it means preparing a preseeded installation file so that everything is taken care of.

How to disable Num_Lock

thomas@inf3.ch (Thomas Schwery) — Mon, 16 Aug 2010 14:14:08 +0000

A small note about the most useless key on my keyboard : Num_Lock

I don’t know about you, but when I have numbers to type, I use the line on top of the keyboard and not the numeric pad that, once activated, replaces some keys of my keyboard - Yes, I’m on a laptop.

So, about disabling that key and rendering it useful :

xmodmap -e 'keycode 77 = ISO_Level3_Shift'

Replace the keycode with what corresponds to your numlock key. If you don’t know the keycode, use xev.

Mercurial Repositories

thomas@inf3.ch (Thomas Schwery) — Sat, 14 Aug 2010 22:05:53 +0000

I finally found a way to share the code snipplets that I wrote for a reason or an another with anyone who would have any use for them.

I decided to drop my usual SVN repositories and try another versioning tool : Mercurial. The main reason was that the name sounded cool and that it was really easy to setup some web repository view … I know it’s not really a plus since all VCS provide this feature through a plugin or an another …

xRandr and dual screen

thomas@inf3.ch (Thomas Schwery) — Wed, 09 Jun 2010 18:28:23 +0000

As always when you have to study an exam, you notice something on your computer that doesn’t work … Today was the easy way to connect an external display and use it to … hum … work.

As I don’t use fancy desktop environment, no gui tools are available. That’s not a problem, you just have to do it the easy way: Some obscure key bindings that will launch a script that will do what you wanted.

How to modify the CPU voltage

thomas@inf3.ch (Thomas Schwery) — Mon, 07 Jun 2010 23:08:51 +0000

Hi !

Today I just experimented with an old tool: Linux-PHC. This is a kernel module that replaces the default apci module and allows more control over the cpu. The main function of this module is to allow the user to modify the CPU voltage, usually lower it.

Why would you lower the CPU voltage ? The answer is simple: On a laptop, it means less heat and more battery.

I tried the experiment a long time ago, we still needed to patch and recompile the kernel … Long procedure, boring when the updates come … Now it is possible to just compile a module and insert it, so I decided to try again.

Pretty boot output

thomas@inf3.ch (Thomas Schwery) — Tue, 13 Apr 2010 01:07:15 +0000

I’ve always asked myself how some Linux distributions have pretty lines along the :

Starting ACPI services...                                                                                           [   OK   ]
Starting anac(h)ronistic cron: anacron deferred while on battery power.                                             [   OK   ]
Starting deferred execution scheduler: atd                                                                          [   OK   ]

It appears this is managed by the LSB and there is only one file to edit to have anything you want for your boot output :

/etc/lsb-base-logging.sh

log_end_msg () {
    # If no arguments were passed, return
    if [ -z "${1:-}" ]; then
        return 1
    fi

    retval=$1

    log_end_msg_pre "$@"

    # Only do the fancy stuff if we have an appropriate terminal
    # and if /usr is already mounted
    if log_use_fancy_output; then
        RED=`$TPUT setaf 1`
        GREEN=`$TPUT setaf 2`
        YELLOW=`$TPUT setaf 3`
        NORMAL=`$TPUT sgr0`
        $TPUT hpa $((`$TPUT cols` - 12))
    else
        RED=''
        GREEN=''
        YELLOW=''
        NORMAL=''
    fi

    if [ $1 -eq 0 ]; then
        /bin/echo -e " [   ${GREEN}OK${NORMAL}   ]"
    elif [ $1 -eq 255 ]; then
        /bin/echo -e " [${YELLOW}WARNING!${NORMAL}]"
    else
        /bin/echo -e " [ ${RED}FAILED${NORMAL} ]"
    fi
    log_end_msg_post "$@"
    return $retval
}

log_action_end_msg () {
    log_action_end_msg_pre "$@"
    if [ -z "${2:-}" ]; then
        end=""
    else
        end=" ($2)"
    fi

    /bin/echo -n "${end}"

    # Only do the fancy stuff if we have an appropriate terminal
    # and if /usr is already mounted
    if log_use_fancy_output; then
        RED=`$TPUT setaf 1`
        BLUE=`$TPUT setaf 4`
        NORMAL=`$TPUT sgr0`
        $TPUT hpa $((`$TPUT cols` - 12))
    else
        RED=''
        BLUE=''
        NORMAL=''
    fi


    if [ $1 -eq 0 ]; then
        /bin/echo -e " [  ${BLUE}DONE${NORMAL}  ]"
    else
        /bin/echo -e " [ ${RED}FAILED${NORMAL} ]"
    fi
    log_action_end_msg_post "$@"
}

Thanks to Google and Jonathan McDowell