- <div class="title"><a href="http://people.skolelinux.org/pere/blog/Speeding_up_the_Debian_installer_using_eatmydata_and_dpkg_divert.html">Speeding up the Debian installer using eatmydata and dpkg-divert</a></div>
- <div class="date">16th September 2014</div>
- <div class="body"><p>The <a href="https://www.debian.org/">Debian</a> installer could be
-a lot quicker. When we install more than 2000 packages in
-<a href="http://www.skolelinux.org/">Skolelinux / Debian Edu</a> using
-tasksel in the installer, unpacking the binary packages take forever.
-A part of the slow I/O issue was discussed in
-<a href="https://bugs.debian.org/613428">bug #613428</a> about too
-much file system sync-ing done by dpkg, which is the package
-responsible for unpacking the binary packages. Other parts (like code
-executed by postinst scripts) might also sync to disk during
-installation. All this sync-ing to disk do not really make sense to
-me. If the machine crash half-way through, I start over, I do not try
-to salvage the half installed system. So the failure sync-ing is
-supposed to protect against, hardware or system crash, is not really
-relevant while the installer is running.</p>
-
-<p>A few days ago, I thought of a way to get rid of all the file
-system sync()-ing in a fairly non-intrusive way, without the need to
-change the code in several packages. The idea is not new, but I have
-not heard anyone propose the approach using dpkg-divert before. It
-depend on the small and clever package
-<a href="https://packages.qa.debian.org/eatmydata">eatmydata</a>, which
-uses LD_PRELOAD to replace the system functions for syncing data to
-disk with functions doing nothing, thus allowing programs to live
-dangerous while speeding up disk I/O significantly. Instead of
-modifying the implementation of dpkg, apt and tasksel (which are the
-packages responsible for selecting, fetching and installing packages),
-it occurred to me that we could just divert the programs away, replace
-them with a simple shell wrapper calling
-"eatmydata $program $@", to get the same effect.
-Two days ago I decided to test the idea, and wrapped up a simple
-implementation for the Debian Edu udeb.</p>
-
-<p>The effect was stunning. In my first test it reduced the running
-time of the pkgsel step (installing tasks) from 64 to less than 44
-minutes (20 minutes shaved off the installation) on an old Dell
-Latitude D505 machine. I am not quite sure what the optimised time
-would have been, as I messed up the testing a bit, causing the debconf
-priority to get low enough for two questions to pop up during
-installation. As soon as I saw the questions I moved the installation
-along, but do not know how long the question were holding up the
-installation. I did some more measurements using Debian Edu Jessie,
-and got these results. The time measured is the time stamp in
-/var/log/syslog between the "pkgsel: starting tasksel" and the
-"pkgsel: finishing up" lines, if you want to do the same measurement
-yourself. In Debian Edu, the tasksel dialog do not show up, and the
-timing thus do not depend on how quickly the user handle the tasksel
-dialog.</p>
-
-<p><table>
-
-<tr>
-<th>Machine/setup</th>
-<th>Original tasksel</th>
-<th>Optimised tasksel</th>
-<th>Reduction</th>
-</tr>
-
-<tr>
-<td>Latitude D505 Main+LTSP LXDE</td>
-<td>64 min (07:46-08:50)</td>
-<td><44 min (11:27-12:11)</td>
-<td>>20 min 18%</td>
-</tr>
-
-<tr>
-<td>Latitude D505 Roaming LXDE</td>
-<td>57 min (08:48-09:45)</td>
-<td>34 min (07:43-08:17)</td>
-<td>23 min 40%</td>
-</tr>
-
-<tr>
-<td>Latitude D505 Minimal</td>
-<td>22 min (10:37-10:59)</td>
-<td>11 min (11:16-11:27)</td>
-<td>11 min 50%</td>
-</tr>
-
-<tr>
-<td>Thinkpad X200 Minimal</td>
-<td>6 min (08:19-08:25)</td>
-<td>4 min (08:04-08:08)</td>
-<td>2 min 33%</td>
-</tr>
-
-<tr>
-<td>Thinkpad X200 Roaming KDE</td>
-<td>19 min (09:21-09:40)</td>
-<td>15 min (10:25-10:40)</td>
-<td>4 min 21%</td>
-</tr>
-
-</table></p>
-
-<p>The test is done using a netinst ISO on a USB stick, so some of the
-time is spent downloading packages. The connection to the Internet
-was 100Mbit/s during testing, so downloading should not be a
-significant factor in the measurement. Download typically took a few
-seconds to a few minutes, depending on the amount of packages being
-installed.</p>
-
-<p>The speedup is implemented by using two hooks in
-<a href="https://www.debian.org/devel/debian-installer/">Debian
-Installer</a>, the pre-pkgsel.d hook to set up the diverts, and the
-finish-install.d hook to remove the divert at the end of the
-installation. I picked the pre-pkgsel.d hook instead of the
-post-base-installer.d hook because I test using an ISO without the
-eatmydata package included, and the post-base-installer.d hook in
-Debian Edu can only operate on packages included in the ISO. The
-negative effect of this is that I am unable to activate this
-optimization for the kernel installation step in d-i. If the code is
-moved to the post-base-installer.d hook, the speedup would be larger
-for the entire installation.</p>
-
-<p>I've implemented this in the
-<a href="https://packages.qa.debian.org/debian-edu-install">debian-edu-install</a>
-git repository, and plan to provide the optimization as part of the
-Debian Edu installation. If you want to test this yourself, you can
-create two files in the installer (or in an udeb). One shell script
-need do go into /usr/lib/pre-pkgsel.d/, with content like this:</p>
-
-<p><blockquote><pre>
-#!/bin/sh
-set -e
-. /usr/share/debconf/confmodule
-info() {
- logger -t my-pkgsel "info: $*"
-}
-error() {
- logger -t my-pkgsel "error: $*"
-}
-override_install() {
- apt-install eatmydata || true
- if [ -x /target/usr/bin/eatmydata ] ; then
- for bin in dpkg apt-get aptitude tasksel ; do
- file=/usr/bin/$bin
- # Test that the file exist and have not been diverted already.
- if [ -f /target$file ] ; then
- info "diverting $file using eatmydata"
- printf "#!/bin/sh\neatmydata $bin.distrib \"\$@\"\n" \
- > /target$file.edu
- chmod 755 /target$file.edu
- in-target dpkg-divert --package debian-edu-config \
- --rename --quiet --add $file
- ln -sf ./$bin.edu /target$file
- else
- error "unable to divert $file, as it is missing."
- fi
- done
- else
- error "unable to find /usr/bin/eatmydata after installing the eatmydata pacage"
- fi
-}
-
-override_install
-</pre></blockquote></p>
-
-<p>To clean up, another shell script should go into
-/usr/lib/finish-install.d/ with code like this:
-
-<p><blockquote><pre>
-#! /bin/sh -e
-. /usr/share/debconf/confmodule
-error() {
- logger -t my-finish-install "error: $@"
-}
-remove_install_override() {
- for bin in dpkg apt-get aptitude tasksel ; do
- file=/usr/bin/$bin
- if [ -x /target$file.edu ] ; then
- rm /target$file
- in-target dpkg-divert --package debian-edu-config \
- --rename --quiet --remove $file
- rm /target$file.edu
- else
- error "Missing divert for $file."
- fi
- done
- sync # Flush file buffers before continuing
-}
-
-remove_install_override
-</pre></blockquote></p>
-
-<p>In Debian Edu, I placed both code fragments in a separate script
-edu-eatmydata-install and call it from the pre-pkgsel.d and
-finish-install.d scripts.</p>
-
-<p>By now you might ask if this change should get into the normal
-Debian installer too? I suspect it should, but am not sure the
-current debian-installer coordinators find it useful enough. It also
-depend on the side effects of the change. I'm not aware of any, but I
-guess we will see if the change is safe after some more testing.
-Perhaps there is some package in Debian depending on sync() and
-fsync() having effect? Perhaps it should go into its own udeb, to
-allow those of us wanting to enable it to do so without affecting
-everyone.</p>
+ <div class="title"><a href="http://people.skolelinux.org/pere/blog/Simpler_recipe_on_how_to_make_a_simple__7_IMSI_Catcher_using_Debian.html">Simpler recipe on how to make a simple $7 IMSI Catcher using Debian</a></div>
+ <div class="date"> 9th August 2017</div>
+ <div class="body"><p>On friday, I came across an interesting article in the Norwegian
+web based ICT news magazine digi.no on
+<a href="https://www.digi.no/artikler/sikkerhetsforsker-lagde-enkel-imsi-catcher-for-60-kroner-na-kan-mobiler-kartlegges-av-alle/398588">how
+to collect the IMSI numbers of nearby cell phones</a> using the cheap
+DVB-T software defined radios. The article refered to instructions
+and <a href="https://www.youtube.com/watch?v=UjwgNd_as30">a recipe by
+Keld Norman on Youtube on how to make a simple $7 IMSI Catcher</a>, and I decided to test them out.</p>
+
+<p>The instructions said to use Ubuntu, install pip using apt (to
+bypass apt), use pip to install pybombs (to bypass both apt and pip),
+and the ask pybombs to fetch and build everything you need from
+scratch. I wanted to see if I could do the same on the most recent
+Debian packages, but this did not work because pybombs tried to build
+stuff that no longer build with the most recent openssl library or
+some other version skew problem. While trying to get this recipe
+working, I learned that the apt->pip->pybombs route was a long detour,
+and the only piece of software dependency missing in Debian was the
+gr-gsm package. I also found out that the lead upstream developer of
+gr-gsm (the name stand for GNU Radio GSM) project already had a set of
+Debian packages provided in an Ubuntu PPA repository. All I needed to
+do was to dget the Debian source package and built it.</p>
+
+<p>The IMSI collector is a python script listening for packages on the
+loopback network device and printing to the terminal some specific GSM
+packages with IMSI numbers in them. The code is fairly short and easy
+to understand. The reason this work is because gr-gsm include a tool
+to read GSM data from a software defined radio like a DVB-T USB stick
+and other software defined radios, decode them and inject them into a
+network device on your Linux machine (using the loopback device by
+default). This proved to work just fine, and I've been testing the
+collector for a few days now.</p>
+
+<p>The updated and simpler recipe is thus to</p>
+
+<ol>
+
+<li>start with a Debian machine running Stretch or newer,</li>
+
+<li>build and install the gr-gsm package available from
+<a href="http://ppa.launchpad.net/ptrkrysik/gr-gsm/ubuntu/pool/main/g/gr-gsm/">http://ppa.launchpad.net/ptrkrysik/gr-gsm/ubuntu/pool/main/g/gr-gsm/</a>,</li>
+
+<li>clone the git repostory from <a href="https://github.com/Oros42/IMSI-catcher">https://github.com/Oros42/IMSI-catcher</a>,</li>
+
+<li>run grgsm_livemon and adjust the frequency until the terminal
+where it was started is filled with a stream of text (meaning you
+found a GSM station).</li>
+
+<li>go into the IMSI-catcher directory and run 'sudo python simple_IMSI-catcher.py' to extract the IMSI numbers.</li>
+
+</ol>
+
+<p>To make it even easier in the future to get this sniffer up and
+running, I decided to package
+<a href="https://github.com/ptrkrysik/gr-gsm/">the gr-gsm project</a>
+for Debian (<a href="https://bugs.debian.org/871055">WNPP
+#871055</a>), and the package was uploaded into the NEW queue today.
+Luckily the gnuradio maintainer has promised to help me, as I do not
+know much about gnuradio stuff yet.</p>
+
+<p>I doubt this "IMSI cacher" is anywhere near as powerfull as
+commercial tools like
+<a href="https://www.thespyphone.com/portable-imsi-imei-catcher/">The
+Spy Phone Portable IMSI / IMEI Catcher</a> or the
+<a href="https://en.wikipedia.org/wiki/Stingray_phone_tracker">Harris
+Stingray</a>, but I hope the existance of cheap alternatives can make
+more people realise how their whereabouts when carrying a cell phone
+is easily tracked. Seeing the data flow on the screen, realizing that
+I live close to a police station and knowing that the police is also
+wearing cell phones, I wonder how hard it would be for criminals to
+track the position of the police officers to discover when there are
+police near by, or for foreign military forces to track the location
+of the Norwegian military forces, or for anyone to track the location
+of government officials...</p>
+
+<p>It is worth noting that the data reported by the IMSI-catcher
+script mentioned above is only a fraction of the data broadcasted on
+the GSM network. It will only collect one frequency at the time,
+while a typical phone will be using several frequencies, and not all
+phones will be using the frequencies tracked by the grgsm_livemod
+program. Also, there is a lot of radio chatter being ignored by the
+simple_IMSI-catcher script, which would be collected by extending the
+parser code. I wonder if gr-gsm can be set up to listen to more than
+one frequency?</p>
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