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:title: Notes
:status: published
This is a collection of useful free software and commands for various purposes, that didn't quite fit into `my setup description <./setup.html>`_.
.. contents::
Debian
######
Custom live image
-----------------
Sometimes it's quite useful to have your own custom live system image on a USB stick or a CD, e.g. to save a broken installation or to do maintenance work that cannot be done when the system is running. Building a custom image makes it possible to include software packages that are not included by default and to change the general configuration to your liking.
Set up a basic config according to the `manual <https://debian-live.alioth.debian.org/live-manual/stable/manual/html/live-manual.en.html>`_. If the correct directory structure is there and you are able to build the default image, add a `list with additional packages you want <https://debian-live.alioth.debian.org/live-manual/stable/manual/html/live-manual.en.html#864>`_.
My config command looks like this:
.. code-block:: shell
lb config --bootappend-live \
"boot=live config locales=de_DE.UTF-8 keyboard-layouts=de username=wolfi" \
--debian-installer live
This command ensures a that the image has a German locale and keyboard layout. I also specify a custom user name to login. The default password is "live". With this config, it's possible to install the system to a disk.
Package building
----------------
When I build a Debian package from its sources, I only sometimes want to make actual changes to the source code. In most cases, I want to do a `simple backport <https://wiki.debian.org/SimpleBackportCreation>`_ of a newer package from Testing or Unstable. So it's very annoying if the package build includes test cases that take quite some time to run. You can add ``DEB_BUILD_OPTIONS=nocheck`` to your ``dpkg-buildpackage`` command to skip the test cases.
Emacs
#####
I do nearly all my text editing in `Emacs <https://www.gnu.org/software/emacs/>`_. I write all my code in Emacs, edit configuration files in Emacs, write LaTeX documents with the great `AUCTEX <https://www.gnu.org/software/auctex/>`_ package and do my email with `mu4e <https://www.djcbsoftware.nl/code/mu/mu4e.html>`_. The text you are reading right now was also written in Emacs. You can find a partially cleaned up version of my Emacs config file `here <https://code.fossencdi.org/config.git/tree/emacs>`_. I use the `"tomorrow" theme <https://github.com/purcell/color-theme-sanityinc-tomorrow>`_. Packages are maintained with `El-Get <http://tapoueh.org/emacs/el-get.html>`_.
To securely send email in Emacs, I do certificate pinning with GnuTLS as described `here <https://blogs.fsfe.org/jens.lechtenboerger/2014/03/10/certificate-pinning-with-gnutls-in-the-mess-of-ssltls/>`__. My mail server uses `Let’s Encrypt <https://letsencrypt.org/>`_, so I have to do the pinning every two months. The procedure is as follows:
.. code-block:: shell
$ gnutls-cli --tofu --crlf --starttls -p 587 example.com
EHLO localhost
STARTTLS
Then press ``Ctrl-D``.
If you work with others on a software project or if you want to write clean code in general, it's important to properly use whitespace. With the command ``whitespace-cleanup``, you can get rid of unnecessary whitespace at the end of lines or in otherwise empty lines.
Open a file as root in Emacs:
.. code-block:: shell
C-x C-f /sudo::/path/to/file
Files and storage
#################
Count number of words in a PDF document:
.. code-block:: shell
pdftotext <FILE> - | tr -d '.' | wc -w -
`pmount <http://linux.die.net/man/1/pmount>`_ can be used to manually mount removable mass storage as normal user.
Network
#######
View network connections continously:
.. code-block:: shell
netstat -t -u -c
List the programs that currently use a specific network interface:
.. code-block:: shell
sudo nethogs <INTERFACE>
Profiling applications
######################
Collect function calls with callgrind without fancy options:
.. code-block:: shell
valgrind --tool=callgrind <APP>
Results can be viewed in KCachegrind.
Media
#####
I do all my video editing and the occasional 3D modeling with the allrounder `Blender <https://www.blender.org/>`_. Vector graphics are created in `Inkscape <https://inkscape.org/en/>`_.
Photos
------
`Geeqie <http://geeqie.sourceforge.net/>`_ is a really nice and fast program to browse the RAW image files of your camera. I get the best out of my RAW images by editing them with `Rawtherapee <http://www.rawtherapee.com/>`_. `Gimp <https://www.gimp.org/>`_ is used for everything else that Rawtherapee can't do. HDR images can be created with `Luminance HDR <http://qtpfsgui.sourceforge.net/>`_.
If I want to publish an image on the web, I first export it as JPEG, remove EXIF data with ``exiftool -all= IMAGE.jpg`` and optimize it with ``jpegoptim -s IMAGE.jpg``.
Record screen
-------------
Set the screen size with the ``-s`` option: wuxga for 1920x1200 and wxga for 1366x768.
.. code-block:: shell
avconv -f x11grab -s wuxga -r 25 -i :0.0 -qscale 5 -an OUTPUT.avi
Openwrt
#######
I build the `Openwrt <https://openwrt.org/>`_ images for my routers from source. This way I can benefit from the security updates that are backported to the stable branches. The official prebuilt images are normally not updated when there are security issues. Additionally, I can add packages to the image, so I don't have to rely on the binary package manager. This also saves space. To update the sources, a few steps are needed:
.. code-block:: shell
git pull
./scripts/feeds update -a
./scripts/feeds install -a
The newly build images can be found in the ``bin`` folder in a directory with the name of the platform the router is based on.
I use `Unbound <https://unbound.net/>`_ as a recursive DNS resolver on my routers for all devices that are behind it. After upgrading the routers, it's necessary to sync the time. Otherwise, resolving DNS entries will fail.
Replicant
#########
The phone's storage can be manually mounted with ``jmtpfs /media/phone/`` and unmounted with ``fusermount -u /media/phone``.
I work on a `Replicant version based on CyanogenMod 13 <https://redmine.replicant.us/boards/21/topics/12057>`_. Alpha releases are tagged on the stable branch. There are too many git repositories in order to do the tagging manually, so I came up with two commands. First to add signed tags to all the repos that are directly mirrored from CyanogenMod:
.. code-block:: shell
repo forall $(repo forall -c ' echo "$REPO_REMOTE$REPO_PROJECT" | grep cm-mirror | cut -c10-') \
-c ' git tag -s replicant-6.0-alpha-0002 -m "second alpha release of Replicant 6.0" && \
git push git@fossencdi.org:cm-mirror/$REPO_PROJECT replicant-6.0-alpha-0002 '
Then sign all the modified repos:
.. code-block:: shell
repo forall $(repo forall -c ' echo "$REPO_REMOTE$REPO_PROJECT" | grep fossencdi | cut -c10-') \
-c ' git tag -s replicant-6.0-alpha-0002 -m "second alpha release of Replicant 6.0" && \
git push git@fossencdi.org:$REPO_PROJECT replicant-6.0-alpha-0002 '
GDB debugging
-------------
Set the path of your Android GDB installation in the development repo, e.g.:
.. code-block:: diff
diff --git a/scripts/gdbclient b/scripts/gdbclient
index 8ff9ae9..5357d38 100755
--- a/scripts/gdbclient
+++ b/scripts/gdbclient
@@ -34,7 +34,7 @@ function gdbwrapper()
{
local GDB_CMD="$1"
shift 1
- $GDB_CMD -x "$@"
+ toolchain/gdb/install/bin/arm-elf-linux-gdb -x "$@"
}
function gdbclient() {
Get a gdbserver binary, push it to the device and start it for the binary you want to monitor. An example for debugging surfaceflinger:
.. code-block:: shell
adb push gdbserver /system/bin/
adb shell "gdbserver 127.0.0.1:5039 /system/bin/surfaceflinger" &
Then run the gdbclient script with the PID as option.
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