Search Results: "ron"

16 October 2022

Sven Hoexter: CentOS 9, stunnel, an openssl memory leak and a VirtualBox crash

tl;dr; OpenSSL 3.0.1 leaks memory in ssl3_setup_write_buffer(), seems to be fixed in 3.0.5 3.0.2. The issue manifests at least in stunnel and keepalived on CentOS 9. In addition I learned the hard way that running a not so recent VirtualBox version on Debian bullseye let to dh parameter generation crashing in libcrypto in bn_sqr8x_internal(). A recent rabbit hole I went down. The actual bug in openssl was nailed down and documented by Quentin Armitage on GitHub in keepalived My bugreport with all back and forth in the RedHat Bugzilla is #2128412. Act I - Hello stunnel, this is the OOMkiller Calling We started to use stunnel on Google Cloud compute engine instances running CentOS 9. The loadbalancer in front of those instances used a TCP health check to validate the backend availability. A day or so later the stunnel instances got killed by the OOMkiller. Restarting stunnel and looking into /proc/<pid>/smaps showed a heap segment growing quite quickly. Act II - Reproducing the Issue While I'm not the biggest fan of VirtualBox and Vagrant I've to admit it's quite nice to just fire up a VM image, and give other people a chance to recreate that setup as well. Since VirtualBox is no longer released with Debian/stable I just recompiled what was available in unstable at the time of the bullseye release, and used that. That enabled me now to just start a CentOS 9 VM, setup stunnel with a minimal config, grab netcat and a for loop and watch the memory grow. E.g. while true; do nc -z localhost 2600; sleep 1; done To my surprise, in addition to the memory leak, I also observed some crashes but did not yet care too much about those. Act III - Wrong Suspect, a Workaround and Bugreporting Of course the first idea was that something must be wrong in stunnel itself. But I could not find any recent bugreports. My assumption is that there are still a few people around using CentOS and stunnel, so someone else should probably have seen it before. Just to be sure I recompiled the latest stunnel package from Fedora. Didn't change anything. Next I recompiled it without almost all the patches Fedora/RedHat carries. Nope, no progress. Next idea: Maybe this is related to the fact that we do not initiate a TLS context after connecting? So we changed the test case from nc to openssl s_client, and the loadbalancer healthcheck from TCP to a TLS based one. Tada, a workaround, no more memory leaking. In addition I gave Fedora a try (they have Vagrant Virtualbox images in the "Cloud" Spin, e.g. here for Fedora 36) and my local Debian installation a try. No leaks experienced on both. Next I reported #2128412. Act IV - Crash in libcrypto and a VirtualBox Bug When I moved with the test case from the Google Cloud compute instance to my local VM I encountered some crashes. That morphed into a real problem when I started to run stunnel with gdb and valgrind. All crashes happened in libcrypto bn_sqr8x_internal() when generating new dh parameter (stunnel does that for you if you do not use static dh parameter). I quickly worked around that by generating static dh parameter for stunnel. After some back and forth I suspected VirtualBox as the culprit. Recompiling the current VirtualBox version (6.1.38-dfsg-3) from unstable on bullseye works without any changes. Upgrading actually fixed that issue. Epilog I highly appreciate that RedHat, with all the bashing around the future of CentOS, still works on community contributed bugreports. My kudos go to Clemens Lang. :) Now that the root cause is clear, I guess RedHat will push out a fix for the openssl 3.0.1 based release they have in RHEL/CentOS 9. Until that is available at least stunnel and keepalived are known to be affected. If you run stunnel on something public it's not that pretty, because already a low rate of TCP connections will result in a DoS condition.

Colin Watson: Reproducible man-db databases

I ve released man-db 2.11.0 (announcement, NEWS), and uploaded it to Debian unstable. The biggest chunk of work here was fixing some extremely long-standing issues with how the database is built. Despite being in the package name, man-db s database is much less important than it used to be: most uses of man(1) haven t required it in a long time, and both hardware and software improvements mean that even some searches can be done by brute force without needing prior indexing. However, the database is still needed for the whatis(1) and apropos(1) commands. The database has a simple format - no relational structure here, it s just a simple key-value database using old-fashioned DBM-like interfaces and composing a few fields to form values - but there are a number of subtleties involved. The issues tend to amount to this: what does a manual page name mean? At first glance it might seem simple, because you have file names that look something like /usr/share/man/man1/ls.1.gz and that s obviously ls(1). Some pages are symlinks to other pages (which we track separately because it makes it easier to figure out which entries to update when the contents of the file system change), and sometimes multiple pages are even hard links to the same file. The real complications come with whatis references . Pages can list a bunch of names in their NAME section, and the historical expectation is that it should be possible to use those names as arguments to man(1) even if they don t also appear in the file system (although Debian policy has deprecated relying on this for some time). Not only does that mean that man(1) sometimes needs to consult the database, but it also means that the database is inherently more complicated, since a page might list something in its NAME section that conflicts with an actual file name in the file system, and now you need a priority system to resolve ambiguities. There are some other possible causes of ambiguity as well. The people working on reproducible builds in Debian branched out to the related challenge of reproducible installations some time ago: can you take a collection of packages, bootstrap a file system image from them, and reproduce that exact same image somewhere else? This is useful for the same sorts of reasons that reproducible builds are useful: it lets you verify that an image is built from the components it s supposed to be built from, and doesn t contain any other skulduggery by accident or design. One of the people working on this noticed that man-db s database files were an obstacle to that: in particular, the exact contents of the database seemed to depend on the order in which files were scanned when building it. The reporter proposed solving this by processing files in sorted order, but I wasn t keen on that approach: firstly because it would mean we could no longer process files in an order that makes it more efficient to read them all from disk (still valuable on rotational disks), but mostly because the differences seemed to point to other bugs. Having understood this, there then followed several late nights of very fiddly work on the details of how the database is maintained. None of this was conceptually difficult: it mainly amounted to ensuring that we maintain a consistent well-order for different entries that we might want to insert for a given database key, and that we consider the same names for insertion regardless of the order in which we encounter files. As usual, the tricky bit is making sure that we have the right data structures to support this. man-db is written in C which is not very well-supplied with built-in data structures, and originally much of the code was written in a style that tried to minimize memory allocations; this came at the cost of ownership and lifetime often being rather unclear, and it was often difficult to make changes without causing leaks or double-frees. Over the years I ve been gradually introducing better encapsulation to make things easier to follow, and I had to do another round of that here. There were also some problems with caching being done at slightly the wrong layer: we need to make use of a trace of the chain of links followed to resolve a page to its ultimate source file, but we were incorrectly caching that trace and reusing it for any link to the same file, with incorrect results in many cases. Oh, and after doing all that I found that the on-disk representation of a GDBM database is insertion-order-dependent, so I ended up having to manually reorganize the database at the end by reading it all in and writing it all back out in sorted order, which feels really weird to me coming from spending most of my time with PostgreSQL these days. Fortunately the database is small so this takes negligible time. None of this is particularly glamorous work, but it paid off:
# export SOURCE_DATE_EPOCH="$(date +%s)"
# mkdir emptydir disorder
# disorderfs --multi-user=yes --shuffle-dirents=yes --reverse-dirents=no emptydir disorder
# export TMPDIR="$(pwd)/disorder"
# mmdebstrap --variant=standard --hook-dir=/usr/share/mmdebstrap/hooks/merged-usr \
      unstable out1.tar
# mmdebstrap --variant=standard --hook-dir=/usr/share/mmdebstrap/hooks/merged-usr \
      unstable out2.tar
# cmp out1.tar out2.tar
# echo $?
0

Vincent Fourmond: Tutorial: analysis of multiwavelength fast kinetics data

The purpose of this post is to demonstrate a first approach to the analysis of multiwavelength kinetic data, like those obtained using stopped-flow data. To practice, we will use data that were acquired during the stopped flow practicals of the MetBio summer school from the FrenchBIC. During the practicals, the student monitored the reaction of myoglobin (in its Fe(III) state) with azide, which yields a fast and strong change in the absorbance spectrum of the protein, which was monitored using a diode array. The data is publicly available on zenodo. Aims of this tutorial The purpose of this tutorial is to teach you to use the free softwareQSoas to run a simple, multiwavelength exponential fit on the data, and to look at the results. This is not a kinetics lecture, so that it will not go in depth about the use of the exponential fit and its meaning. Getting started: loading the file First, make sure you have a working version of QSoas, you can download them (for free) there. Then download the data files from zenodo. We will work only on the data file Azide-1.25mm_001.dat, but of course, the purpose of this tutorial is to enable you to work on all of them. The data files contain the time evolution of the absorbance for all wavelengths, in a matrix format, in which each row correpond to a time point and each column to a wavelength. Start QSoas, and launch the command:
QSoas> load /comments='"'
Then, choose the Azide-1.25mm_001.dat data file. This should bring up a horizontal red line at the bottom of the data display, with X values between about 0 and 2.5. If you zoom on the red line with the mouse wheel, you'll realize it is data. The /comments='"' part is very important since it allows the extraction of the wavelength from the data. We will look at what it means another day. At this stage, you can look at the loaded data using the command:
QSoas> edit
You should have a window looking like this:
The rows each correspond to a data point displayed on the window below. The first column correspond to the X values, the second the Y values, and all the other ones to extra Y columns (they are not displayed by default). What is especially interesting is the first row, which contains a nan as the X value and what is obviously the wavelength for all the Y values. To tell that QSoas should take this line as the wavelength (which will be the perpendicular coordinate, the coordinate of the other direction of the matrix), first close the edit window and run:
QSoas> set-perp /from-row=0
Splitting and fitting Now, we have a single dataset containing a lot of Y columns. We want to fit all of them simultaneously with a (mono) exponential fit. For that, we first need to split the big matrix into a series of X,Y datasets (because fitting only works on the first Y). This is possible by running:
QSoas> expand /style=red-to-blue /flags=kinetics
Your screen should now look like this:
You're looking at the kinetics at all wavelengths at the same time (this may take some time to display on your computer, it is after all a rather large number of data points). The /style=red-to-blue is not strictly necessary, but it gives the red to blue color gradient which makes things easier to look at (and cooler !). The /flags=kinetics is there to attach a label (a flag) to the newly created datasets so we can easily manipulate all of them at the same time. Then it's time to fit, with the following command:
QSoas> mfit-exponential-decay flagged:kinetics
This should bring up a new window. After resizing it, you should have something that looks like this:
The bottom of the fit window is taken by the parameters, each with two checkboxes on the right to set them fixed (i.e. not determined by the fitting mechanism) and/or global (i.e. with a single value for all the datasets, here all the wavelengths). The top shows the current dataset along with the corresponding fit (in green), and, below, the residuals. You can change the dataset by clicking on the horizontal arrows or using Ctrl+PgUp or Ctrl+PgDown (keep holding it to scan fast). See the Z = 728.15 showing that QSoas has recognized that the currently displayed dataset corresponds to the wavelength 728.15. The equation fitted to the data is: $$y(x) = A_\infty + A_1 \times \exp -(x - x_0)/\tau_1$$ In this case, while the \(A_1\) and \(A_\infty\) parameters clearly depend on the wavelength, the time constant of evolution should be independent of wavelength (the process happens at a certain rate regardless of the wavelength we're analyzing), so that the \(\tau_1\) parameter should be common for all the datasets/wavelengths. Just click on the global checkbox at the right of the tau_1 parameter, make sure it is checked, and hit the Fit button... The fit should not take long (less than a minute), and then you end up with the results of the fits: all the parameters. The best way to look at the non global parameters like \(A_1\) and \(A_\infty\) is to use the Show Parameters item from the Parameters menu. Using it and clicking on A_inf too should give you a display like this one:
The A_inf parameter corresponds to the spectum at infinite time (of azide-bound heme), while the A_1 parameter corresponds to the difference spectrum between the initial (azide-free) and final (azide-bound) states. Now, the fit is finished, you can save the parameters if you want to reload them in a later fit by using the Parameters/Save menu item or export them in a form more suitable for plotting using Parameters/Export (although QSoas can also display and the parameters saved using Save). This concludes this first approach to fitting the data. What you can do is How to read the code above All the lines starting by QSoas> in the code areas above are meant to be typed into the QSoas command line (at the bottom of the window), and started by pressing enter at the end. You must remove the QSoas> bit. The other lines (when applicable) show you the response of QSoas, in the terminal just above the command-line. You may want to play with the QSoas tutorial to learn more about how to interact with QSoas. About QSoas QSoas is a powerful open source data analysis program that focuses on flexibility and powerful fitting capacities. It is released under the GNU General Public License. It is described in Fourmond, Anal. Chem., 2016, 88 (10), pp 5050 5052. Current version is 3.1. You can freely (and at no cost) download its source code or precompiled versions for MacOS and Windows there. Alternatively, you can clone from the GitHub repository.
Contact: find my email address there, or contact me on LinkedIn.

14 October 2022

Shirish Agarwal: Dowry, Racism, Railways

Dowry Few days back, had posted about the movie Raksha Bandhan and whatever I felt about it. Sadly, just couple of days back, somebody shared this link. Part of me was shocked and part of me was not. Couple of acquaintances of mine in the past had said the same thing for their daughters. And in such situations you are generally left speechless because you don t know what the right thing to do is. If he has shared it with you being an outsider, how many times he must have told the same to their wife and daughters? And from what little I have gathered in life, many people have justified it on similar lines. And while the protests were there, sadly the book was not removed. Now if nurses are reading such literature, how their thought process might be forming, you can tell :(. And these are the ones whom we call for when we are sick and tired :(. And I have not taken into account how the girls/women themselves might be feeling. There are similar things in another country but probably not the same, nor the same motivations though although feeling helplessness in both would be a common thing. But such statements are not alone. Another gentleman in slightly different context shared this as well
The above is a statement shared in a book recommended for CTET (Central Teacher s Eligibility Test that became mandatory to be taken as the RTE (Right To Education) Act came in.). The statement says People from cold places are white, beautiful, well-built, healthy and wise. And people from hot places are black, irritable and of violent nature. Now while I can agree with one part of the statement that people residing in colder regions are more fair than others but there are loads of other factors that determine fairness or skin color/skin pigmentation. After a bit of search came to know that this and similar articulation have been made in an idea/work called Environmental Determinism . Now if you look at that page, you would realize this was what colonialism is and was all about. The idea that the white man had god-given right to rule over others. Similarly, if you are fair, you can lord over others. Seems simplistic, but yet it has a powerful hold on many people in India. Forget the common man, this thinking is and was applicable to some of our better-known Freedom fighters. Pune s own Bal Gangadhar Tilak The Artic Home to the Vedas. It sort of talks about Aryans and how they invaded India and became settled here. I haven t read or have access to the book so have to rely on third-party sources. The reason I m sharing all this is that the right-wing has been doing this myth-making for sometime now and unless and until you put a light on it, it will continue to perpetuate  . For those who have read this blog, do know that India is and has been in casteism from ever. They even took the fair comment and applied it to all Brahmins. According to them, all Brahmins are fair and hence have god-given right to lord over others. What is called the Eton boy s network serves the same in this casteism. The only solution is those idea under limelight and investigate. To take the above, how does one prove that all fair people are wise and peaceful while all people black and brown are violent. If that is so, how does one count for Mahatma Gandhi, Martin Luther King Junior, Nelson Mandela, Michael Jackson the list is probably endless. And not to forget that when Mahatma Gandhiji did his nonviolent movements either in India or in South Africa, both black and brown people in millions took part. Similar examples of Martin Luther King Jr. I know and read of so many non-violent civl movements that took place in the U.S. For e.g. Rosa Parks and the Montgomery Bus Boycott. So just based on these examples, one can conclude that at least the part about the fair having exclusive rights to being fair and noble is not correct. Now as far as violence goes, while every race, every community has had done violence in the past or been a victim of the same. So no one is and can be blameless, although in light of the above statement, the question can argumentated as to who were the Vikings? Both popular imagination and serious history shares stories about Vikings. The Vikings were somewhat nomadic in nature even though they had permanent settlements but even then they went on raids, raped women, captured both men and women and sold them at slaves. So they are what pirates came to be, but not the kind Hollywood romanticizes about. Europe in itself has been a tale in conflict since time immemorial. It is only after the formation of EU that most of these countries stopped fighting each other From a historical point perspective, it is too new. So even the part of fair being non-violent dies in face of this evidence. I could go on but this is enough on that topic.

Railways and Industrial Action around the World. While I have shared about Railways so many times on this blog, it continues to fascinate me that how people don t understand the first things about Railways. For e.g. Railways is a natural monopoly. What that means is and you can look at all and any type of privatization around the world, you will see it is a monopoly. Unlike the road or Skies, Railways is and would always be limited by infrastructure and the ability to have new infrastructure. Unlike in road or Skies (even they have their limits) you cannot run train services on a whim. At any particular point in time, only a single train could and should occupy a stretch of Railway network. You could have more trains on one line, but then the likelihood of front or rear-end collisions becomes a real possibility. You also need all sorts of good and reliable communications, redundant infrastructure so if one thing fails then you have something in place. The reason being a single train can carry anywhere from 2000 to 5000 passengers or more. While this is true of Indian Railways, Railways around the world would probably have some sort of similar numbers.It is in this light that I share the below videos.
To be more precise, see the fuller video
Now to give context to the recording above, Mike Lynch is the general secretary at RMT. For those who came in late, both UK and the U.S. have been threatened by railway strikes. And the reason for the strikes or threat of strikes is similar. Now from the company perspective, all they care is to invest less and make the most profits that can be given to equity shareholders. At the same time, they have freezed the salaries of railway workers for the last 3 years. While the politicians who were asking the questions, apparently gave themselves raise twice this year. They are asking them to negotiate at 8% while inflation in the UK has been 12.3% and projected to go higher. And it is not only the money. Since the 1980s when UK privatized the Railways, they stopped investing in the infrastructure. And that meant that the UK Railway infrastructure over period of time started getting behind and is even behind say Indian Railways which used to provide most bang for the buck. And Indian Railways is far from ideal. Ironically, most of the operators on UK are nationalized Railways of France, Germany etc. but after the hard Brexit, they too are mulling to cut their operations short, they have too  There is also the EU Entry/Exit system that would come next year. Why am I sharing about what is happening in UK Rail, because the Indian Government wants to follow the same thing, and fooling the public into saying we would do it better. What inevitably will happen is that ticket prices go up, people no longer use the service, the number of services go down and eventually they are cancelled. This has happened both in Indian Railways as well as Airlines. In fact, GOI just recently announced a credit scheme just a few days back to help Airlines stay afloat. I was chatting with a friend who had come down to Pune from Chennai and the round-trip cost him INR 15k/- on that single trip alone. We reminisced how a few years ago, 8 years to be precise, we could buy an Air ticket for 2.5k/- just a few days before the trip and did it. I remember doing/experiencing at least a dozen odd trips via air in the years before 2014. My friend used to come to Pune, almost every weekend because he could afford it, now he can t do that. And these are people who are in the above 5-10% of the population. And this is not just in UK, but also in the United States. There is one big difference though, the U.S. is mainly a freight carrier while the UK Railway Operations are mostly passenger based. What was and is interesting that Scotland had to nationalize their services as they realized the Operators cannot or will not function when they were most needed. Most of the public even in the UK seem to want a nationalized rail service, at least their polls say so. So, it would definitely be interesting to see what happens in the UK next year. In the end, I know I promised to share about books, but the above incidents have just been too fascinating to not just share the news but also share what I think about them. Free markets function good where there is competition, for example what is and has been happening in China for EV s but not where you have natural monopolies. In all Railway privatization, you have to handover the area to one person, then they have no motivation. If you have multiple operators, then there would always be haggling as to who will run the train and at what time. In either scenario, it doesn t work and raises prices while not delivering anything better  I do take examples from UK because lot of things are India are still the legacy of the British. The whole civil department that was created in 1953 is/was a copy of the British civil department at that time and it is to this day. P.S. Just came to know that the UK Chancellor Kwasi Kwarteng was just sacked as UK Chancellor. I do commend Truss for facing the press even though she might be dumped a week later unlike our PM who hasn t faced a single press conference in the last 8 odd years.

https://www.youtube.com/watch?v=oTP6ogBqU7of The difference in Indian and UK politics seems to be that the English are now asking questions while here in India, most people are still sleeping without a care in the world. Another thing to note Minidebconf Palakkad is gonna happen 12-13th November 2022. I am probably not gonna go but would request everyone who wants to do something in free software to attend it. I am not sure whether I would be of any use like this and also when I get back, it would be an empty house. But for people young and old, who want to do anything with free/open source software it is a chance not to be missed. Registration of the same closes on 1st of November 2022. All the best, break a leg  Just read this, beautifully done.

Gunnar Wolf: Learning some Rust with Lars!

A couple of weeks ago, I read a blog post by former Debian Developer Lars Wirzenius offering a free basic (6hr) course on the Rust language to interested free software and open source software programmers. I know Lars offers training courses in programming, and besides knowing him for ~20 years and being proud to consider us to be friends, have worked with him in a couple of projects (i.e. he is upstream for vmdb2, which I maintain in Debian and use for generating the Raspberry Pi Debian images) He is a talented programmer, and a fun guy to be around. I was admitted to the first cohort of students of this course (please note I m not committing him to run free courses ever again! He has said he would consider doing so, specially to offer a different time better suited for people in Asia). I have wanted to learn some Rust for quite some time. About a year ago, I bought a copy of The Rust Programming Language, the canonical book for learning the language, and started reading it But lacked motivation and lost steam halfway through, and without having done even a simple real project beyond the simple book exercises. How has this been? I have enjoyed the course. I must admit I did expect it to be more hands-on from the beginning, but Rust is such a large language and it introduces so many new, surprising concepts. Session two did have two somewhat simple hands-on challenges; by saying they were somewhat simple does not mean we didn t have to sweat to get them to compile and work correctly! I know we will finish this Saturday, and I ll still be a complete newbie to Rust. I know the only real way to wrap my head around a language is to actually have a project that uses it And I have some ideas in mind. However, I don t really feel confident to approach an already existing project and start meddling with it, trying to contribute. What does Rust have that makes it so different? Bufff Variable ownership (borrow checking) and values lifetimes are the most obvious salient idea, but they are relatively simple, as you just cannot forget about them. But understanding (and adopting) idiomatic constructs such as the pervasive use of enums, understanding that errors always have to be catered for by using expect() and Result<T,E> It will take some time to be at ease developing in it, if I ever reach that stage! Oh, FWIW Interested related reading. I am halfway through an interesting article, published in March in the Communications of the ACM magazine, titled Here We Go Again: Why Is It Difficult for Developers to Learn Another Programming Language? , that presents an interesting point we don t always consider: If I m a proficient programmer in the X programming language and want to use the Y programming language, learning it Should be easier for me than for the casual bystander, or not? After all, I already have a background in programming! But it happens that mental constructs we build for a given language might hamper our learning of a very different one. This article presents three interesting research questions:
  1. Does cross-language interference occur?
  2. How do experienced programmers learn new languages?
  3. What do experienced programmers find confusing in new languages?
I m far from reaching the conclusions, but so far, it s been a most interesting read. Anyway, to wrap up Thanks Lars! I am learning (although at a pace that is not magically quick But I am aware of the steep learning curve of the language) quite a bit of a very interesting topic, and I m also enjoying the time I spend in front of my computer on Saturday.

10 October 2022

Ian Jackson: Skipping releases when upgrading Debian systems

Debian does not officially support upgrading from earlier than the previous stable release: you re not supposed to skip releases. Instead, you re supposed to upgrade to each intervening major release in turn. However, skipping intervening releases does, in fact, often work quite well. Apparently, this is surprising to many people, even Debian insiders. I was encouraged to write about it some more. My personal experience I have three conventionally-managed personal server systems (by which I mean systems which aren t reprovisioned by some kind of automation). Of these at least two have been skip upgraded at least once: The one I don t think I ve skip-upgraded (at least, not recently) is my house network manager (and now VM host) which I try to keep to a minimum in terms of functionality and which I keep quite up to date. It was crossgraded from i386 (32-bit) to amd64 (64-bit) fairly recently, which is a thing that Debian isn t sure it supports. The crossgrade was done a hurry and without any planning, prompted by Spectre et al suddenly requiring big changes to Xen. But it went well enough. My home does random stuff server (media server, web cache, printing, DNS, backups etc.), has etckeeper records starting in 2015. I upgraded directly from jessie (Debian 8) to buster (Debian 10). I think it has probably had earlier skip upgrade(s): the oldest file in /etc is from December 1996 and I have been doing occasional skip upgrades as long as I can remember. And of course there s chiark, which is one of the oldest Debian installs in existence. I wrote about the most recent upgrade, where I went directly from jessie i386 ELTS (32-bit Debian 8) to bulleye amd64 (64-bit Debian 11). That was a very extreme case which required significant planning and pre-testing, since the package dependencies were in no way sufficient for the proper ordering. But, I don t normally go to such lengths. Normally, even on chiark, I just edit the sources.list and see what apt proposes to do. I often skip upgrade chiark because I tend to defer risky-looking upgrades partly in the hope of others fixing the bugs while I wait :-), and partly just because change is disruptive and amortising it is very helpful both to me and my users. I have some records of chiark s upgrades from my announcements to users. As well as the recent skip skip up cross grade, direct , I definitely did a skip upgrade of chiark from squeeze (Debian 6) to jessie (Debian 8). It appears that the previous skip upgrade on chiark was rex (Debian 1.2) to hamm (Debian 2.0). I don t think it s usual for me to choose to do a multi-release upgrade the officially supported way, in two (or more) stages, on a server. I have done that on systems with a GUI desktop setup, but even then I usually skip the intermediate reboot(s). When to skip upgrade (and what precautions to take) I m certainly not saying that everyone ought to be doing this routinely. Most users with a Debian install that is older than oldstable probably ought to reinstall it, or do the two-stage upgrade. Skip upgrading almost always runs into some kind of trouble (albeit, usually trouble that isn t particularly hard to fix if you know what you re doing). However, officially supported non-skip upgrades go wrong too. Doing a two-or-more-releases upgrade via the intermediate releases can expose you to significant bugs in the intermediate releases, which were later fixed. Because Debian s users and downstreams are cautious, and Debian itself can be slow, it is common for bugs to appear for one release and then be fixed only in the next. Paradoxically, this seems to be especially true with the kind of big and scary changes where you d naively think the upgrade mechanisms would break if you skipped the release where the change first came in. I would not recommend a skip upgrade to someone who is not a competent Debian administrator, with good familiarity with Debian package management, including use of dpkg directly to fix things up. You should have a mental toolkit of manual bug workaround techniques. I always should make sure that I have rescue media (and in the case of a remote system, full remote access including ability to boot a different image), although I don t often need it. And, when considering a skip upgrade, you should be aware of the major changes that have occurred in Debian. Skip upgrading is more likely to be a good idea with a complex and highly customised system: a fairly vanilla install is not likely to encounter problems during a two-stage update. (And, a vanilla system can be upgraded by reinstalling.) I haven t recently skip upgraded a laptop or workstation. I doubt I would attempt it; modern desktop software seems to take a much harder line about breaking things that are officially unsupported, and generally trying to force everyone into the preferred mold. A request to Debian maintainers I would like to encourage Debian maintainers to defer removing upgrade compatibility machinery until it is actually getting in the way, or has become hazardous, or many years obsolete. Examples of the kinds of things which it would be nice to keep, and which do not usually cause much inconvenience to retain, are dependency declarations (particularly, alternatives), and (many) transitional fragments in maintainer scripts. If you find yourself needing to either delete some compatibility feature, or refactor/reorganise it, I think it is probably best to delete it. If you modify it significantly, the resulting thing (which won t be tested until someone uses it in anger) is quite likely to have bugs which make it go wrong more badly (or, more confusingly) than the breakage that would happen without it. Obviously this is all a judgement call. I m not saying Debian should formally support skip upgrades, to the extent of (further) slowing down important improvements. Nor am I asking for any change to the routine approach to (for example) transitional packages (i.e. the technique for ensuring continuity of installation when a package name changes). We try to make release upgrades work perfectly; but skip upgrades don t have to work perfectly to be valuable. Retaining compatibility code can also make it easier to provide official backports, and it probably helps downstreams with different release schedules. The fact that maintainers do in practice often defer removing compatibility code provides useful flexibility and options to at least some people. So it would be nice if you d at least not go out of your way to break it. Building on older releases I would also like to encourage maintainers to provide source packages in Debian unstable that will still build on older releases, where this isn t too hard and the resulting binaries might be basically functional. Speaking personally, it s not uncommon for me to rebuild packages from unstable and install them on much older releases. This is another thing that is not officially supported, but which often works well. I m not saying to contort your build system, or delay progress. You ll definitely want to depend on a recentish debhelper. But, for example, retaining old build-dependency alternatives is nice. Retaining them doesn t constitute a promise that it works - it just makes life slightly easier for someone who is going off piste. If you know you have users on multiple distros or multiple releases, and wish to fully support them, you can go further, of course. Many of my own packages are directly buildable, or even directly installable, on older releases.

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9 October 2022

Jonathan Dowland: Focus writing with (despite) LaTeX

LaTeX the age-old typesetting system makes me angry. Not because it's bad. To clarify, not because there's something better. But because there should be. When writing a document using LaTeX, if you are prone to procrastination it can be very difficult to focus on the task at hand, because there are so many yaks to shave. Here's a few points of advice. In a nutshell, I think it's wise to move much document reviewing work back into the editor rather than the rendered document, at least in the early stages of a section. And to do that, you need the document to be as legible as possible in the editor. The important stuff is the text you write, not the TeX macros you've sprinkled around to format it. A few tips I benefit from in terms of source formatting: Of course, you need to review the rendered document too! I like to bounce that to a tablet with a pen/stylus/pencil and review it in a different environment to where I write. I then end up with a long list of scrawled notes, and a third distinct activity, back at the writing desk, is to systematically go through them and apply some GTD-style thinking to them: can I fix it in a few seconds? Do it straight away. Delegate it? Unlikely Defer it? transfer the review note into another system of record (such as LaTeX \\todo ). And finally

7 October 2022

Reproducible Builds: Reproducible Builds in September 2022

Welcome to the September 2022 report from the Reproducible Builds project! In our reports we try to outline the most important things that we have been up to over the past month. As a quick recap, whilst anyone may inspect the source code of free software for malicious flaws, almost all software is distributed to end users as pre-compiled binaries. If you are interested in contributing to the project, please visit our Contribute page on our website.
David A. Wheeler reported to us that the US National Security Agency (NSA), Cybersecurity and Infrastructure Security Agency (CISA) and the Office of the Director of National Intelligence (ODNI) have released a document called Securing the Software Supply Chain: Recommended Practices Guide for Developers (PDF). As David remarked in his post to our mailing list, it expressly recommends having reproducible builds as part of advanced recommended mitigations . The publication of this document has been accompanied by a press release.
Holger Levsen was made aware of a small Microsoft project called oss-reproducible. Part of, OSSGadget, a larger collection of tools for analyzing open source packages , the purpose of oss-reproducible is to:
analyze open source packages for reproducibility. We start with an existing package (for example, the NPM left-pad package, version 1.3.0), and we try to answer the question, Do the package contents authentically reflect the purported source code?
More details can be found in the README.md file within the code repository.
David A. Wheeler also pointed out that there are some potential upcoming changes to the OpenSSF Best Practices badge for open source software in relation to reproducibility. Whilst the badge programme has three certification levels ( passing , silver and gold ), the gold level includes the criterion that The project MUST have a reproducible build . David reported that some projects have argued that this reproducibility criterion should be slightly relaxed as outlined in an issue on the best-practices-badge GitHub project. Essentially, though, the claim is that the reproducibility requirement doesn t make sense for projects that do not release built software, and that timestamp differences by themselves don t necessarily indicate malicious changes. Numerous pragmatic problems around excluding timestamps were raised in the discussion of the issue.
Sonatype, a pioneer of software supply chain management , issued a press release month to report that they had found:
[ ] a massive year-over-year increase in cyberattacks aimed at open source project ecosystems. According to early data from Sonatype s 8th annual State of the Software Supply Chain Report, which will be released in full this October, Sonatype has recorded an average 700% jump in repository attacks over the last three years.
More information is available in the press release.
A number of changes were made to the Reproducible Builds website and documentation this month, including Chris Lamb adding a redirect from /projects/ to /who/ in order to keep old or archived links working [ ], Jelle van der Waa added a Rust programming language example for SOURCE_DATE_EPOCH [ ][ ] and Mattia Rizzolo included Protocol Labs amongst our project-level sponsors [ ].

Debian There was a large amount of reproducibility work taking place within Debian this month:
  • The nfft source package was removed from the archive, and now all packages in Debian bookworm now have a corresponding .buildinfo file. This can be confirmed and tracked on the associated page on the tests.reproducible-builds.org site.
  • Vagrant Cascadian announced on our mailing list an informal online sprint to help clear the huge backlog of reproducible builds patches submitted by performing NMU (Non-Maintainer Uploads). The first such sprint took place on September 22nd with the following results:
    • Holger Levsen:
      • Mailed #1010957 in man-db asking for an update and whether to remove the patch tag for now. This was subsequently removed and the maintainer started to address the issue.
      • Uploaded gmp to DELAYED/15, fixing #1009931.
      • Emailed #1017372 in plymouth and asked for the maintainer s opinion on the patch. This resulted in the maintainer improving Vagrant s original patch (and uploading it) as well as filing an issue upstream.
      • Uploaded time to DELAYED/15, fixing #983202.
    • Vagrant Cascadian:
      • Verify and updated patch for mylvmbackup (#782318)
      • Verified/updated patches for libranlip. (#788000, #846975 & #1007137)
      • Uploaded libranlip to DELAYED/10.
      • Verified patch for cclive. (#824501)
      • Uploaded cclive to DELAYED/10.
      • Vagrant was unable to reproduce the underlying issue within #791423 (linuxtv-dvb-apps) and so the bug was marked as done .
      • Researched #794398 (in clhep).
    The plan is to repeat these sprints every two weeks, with the next taking place on Thursday October 6th at 16:00 UTC on the #debian-reproducible IRC channel.
  • Roland Clobus posted his 13th update of the status of reproducible Debian ISO images on our mailing list. During the last month, Roland ensured that the live images are now automatically fed to openQA for automated testing after they have been shown to be reproducible. Additionally Roland asked on the debian-devel mailing list about a way to determine the canonical timestamp of the Debian archive. [ ]
  • Following up on last month s work on reproducible bootstrapping, Holger Levsen filed two bugs against the debootstrap and cdebootstrap utilities. (#1019697 & #1019698)
Lastly, 44 reviews of Debian packages were added, 91 were updated and 17 were removed this month adding to our knowledge about identified issues. A number of issue types have been updated too, including the descriptions of cmake_rpath_contains_build_path [ ], nondeterministic_version_generated_by_python_param [ ] and timestamps_in_documentation_generated_by_org_mode [ ]. Furthermore, two new issue types were created: build_path_used_to_determine_version_or_package_name [ ] and captures_build_path_via_cmake_variables [ ].

Other distributions In openSUSE, Bernhard M. Wiedemann published his usual openSUSE monthly report.

diffoscope diffoscope is our in-depth and content-aware diff utility. Not only can it locate and diagnose reproducibility issues, it can provide human-readable diffs from many kinds of binary formats. This month, Chris Lamb prepared and uploaded versions 222 and 223 to Debian, as well as made the following changes:
  • The cbfstools utility is now provided in Debian via the coreboot-utils package so we can enable that functionality within Debian. [ ]
  • Looked into Mach-O support.
  • Fixed the try.diffoscope.org service by addressing a compatibility issue between glibc/seccomp that was preventing the Docker-contained diffoscope instance from spawning any external processes whatsoever [ ]. I also updated the requirements.txt file, as some of the specified packages were no longer available [ ][ ].
In addition Jelle van der Waa added support for file version 5.43 [ ] and Mattia Rizzolo updated the packaging:
  • Also include coreboot-utils in the Build-Depends and Test-Depends fields so that it is available for tests. [ ]
  • Use pep517 and pip to load the requirements. [ ]
  • Remove packages in Breaks/Replaces that have been obsoleted since the release of Debian bullseye. [ ]

Reprotest reprotest is our end-user tool to build the same source code twice in widely and deliberate different environments, and checking whether the binaries produced by the builds have any differences. This month, reprotest version 0.7.22 was uploaded to Debian unstable by Holger Levsen, which included the following changes by Philip Hands:
  • Actually ensure that the setarch(8) utility can actually execute before including an architecture to test. [ ]
  • Include all files matching *.*deb in the default artifact_pattern in order to archive all results of the build. [ ]
  • Emit an error when building the Debian package if the Debian packaging version does not patch the Python version of reprotest. [ ]
  • Remove an unneeded invocation of the head(1) utility. [ ]

Upstream patches The Reproducible Builds project detects, dissects and attempts to fix as many currently-unreproducible packages as possible. We endeavour to send all of our patches upstream where appropriate. This month, we wrote a large number of such patches, including:

Testing framework The Reproducible Builds project runs a significant testing framework at tests.reproducible-builds.org in order to check packages and other artifacts for reproducibility. This month, however, the following changes were made:
  • Holger Levsen:
    • Add a job to build reprotest from Git [ ] and use the correct Git branch when building it [ ].
  • Mattia Rizzolo:
    • Enable syncing of results from building live Debian ISO images. [ ]
    • Use scp -p in order to preserve modification times when syncing live ISO images. [ ]
    • Apply the shellcheck shell script analysis tool. [ ]
    • In a build node wrapper script, remove some debugging code which was messing up calling scp(1) correctly [ ] and consquently add support to use both scp -p and regular scp [ ].
  • Roland Clobus:
    • Track and handle the case where the Debian archive gets updated between two live image builds. [ ]
    • Remove a call to sudo(1) as it is not (or no longer) required to delete old live-build results. [ ]

Contact As ever, if you are interested in contributing to the Reproducible Builds project, please visit our Contribute page on our website. However, you can get in touch with us via:

6 October 2022

Matthew Garrett: Cloud desktops aren't as good as you'd think

Fast laptops are expensive, cheap laptops are slow. But even a fast laptop is slower than a decent workstation, and if your developers want a local build environment they're probably going to want a decent workstation. They'll want a fast (and expensive) laptop as well, though, because they're not going to carry their workstation home with them and obviously you expect them to be able to work from home. And in two or three years they'll probably want a new laptop and a new workstation, and that's even more money. Not to mention the risks associated with them doing development work on their laptop and then drunkenly leaving it in a bar or having it stolen or the contents being copied off it while they're passing through immigration at an airport. Surely there's a better way?

This is the thinking that leads to "Let's give developers a Chromebook and a VM running in the cloud". And it's an appealing option! You spend far less on the laptop, and the VM is probably cheaper than the workstation - you can shut it down when it's idle, you can upgrade it to have more CPUs and RAM as necessary, and you get to impose all sorts of additional neat security policies because you have full control over the network. You can run a full desktop environment on the VM, stream it to a cheap laptop, and get the fast workstation experience on something that weighs about a kilogram. Your developers get the benefit of a fast machine wherever they are, and everyone's happy.

But having worked at more than one company that's tried this approach, my experience is that very few people end up happy. I'm going to give a few reasons here, but I can't guarantee that they cover everything - and, to be clear, many (possibly most) of the reasons I'm going to describe aren't impossible to fix, they're simply not priorities. I'm also going to restrict this discussion to the case of "We run a full graphical environment on the VM, and stream that to the laptop" - an approach that only offers SSH access is much more manageable, but also significantly more restricted in certain ways. With those details mentioned, let's begin.

The first thing to note is that the overall experience is heavily tied to the protocol you use for the remote display. Chrome Remote Desktop is extremely appealing from a simplicity perspective, but is also lacking some extremely key features (eg, letting you use multiple displays on the local system), so from a developer perspective it's suboptimal. If you read the rest of this post and want to try this anyway, spend some time working with your users to find out what their requirements are and figure out which technology best suits them.

Second, let's talk about GPUs. Trying to run a modern desktop environment without any GPU acceleration is going to be a miserable experience. Sure, throwing enough CPU at the problem will get you past the worst of this, but you're still going to end up with users who need to do 3D visualisation, or who are doing VR development, or who expect WebGL to work without burning up every single one of the CPU cores you so graciously allocated to their VM. Cloud providers will happily give you GPU instances, but that's going to cost more and you're going to need to re-run your numbers to verify that this is still a financial win. "But most of my users don't need that!" you might say, and we'll get to that later on.

Next! Video quality! This seems like a trivial point, but if you're giving your users a VM as their primary interface, then they're going to do things like try to use Youtube inside it because there's a conference presentation that's relevant to their interests. The obvious solution here is "Do your video streaming in a browser on the local system, not on the VM" but from personal experience that's a super awkward pain point! If I click on a link inside the VM it's going to open a browser there, and now I have a browser in the VM and a local browser and which of them contains the tab I'm looking for WHO CAN SAY. So your users are going to watch stuff inside their VM, and re-compressing decompressed video is going to look like shit unless you're throwing a huge amount of bandwidth at the problem. And this is ignoring the additional irritation of your browser being unreadable while you're rapidly scrolling through pages, or terminal output from build processes being a muddy blur of artifacts, or the corner case of "I work for Youtube and I need to be able to examine 4K streams to determine whether changes have resulted in a degraded experience" which is a very real job and one that becomes impossible when you pass their lovingly crafted optimisations through whatever codec your remote desktop protocol has decided to pick based on some random guesses about the local network, and look everyone is going to have a bad time.

The browser experience. As mentioned before, you'll have local browsers and remote browsers. Do they have the same security policy? Who knows! Are all the third party services you depend on going to be ok with the same user being logged in from two different IPs simultaneously because they lost track of which browser they had an open session in? Who knows! Are your users going to become frustrated? Who knows oh wait no I know the answer to this one, it's "yes".

Accessibility! More of your users than you expect rely on various accessibility interfaces, be those mechanisms for increasing contrast, screen magnifiers, text-to-speech, speech-to-text, alternative input mechanisms and so on. And you probably don't know this, but most of these mechanisms involve having accessibility software be able to introspect the UI of applications in order to provide appropriate input or expose available options and the like. So, I'm running a local text-to-speech agent. How does it know what's happening in the remote VM? It doesn't because it's just getting an a/v stream, so you need to run another accessibility stack inside the remote VM and the two of them are unaware of each others existence and this works just as badly as you'd think. Alternative input mechanism? Good fucking luck with that, you're at best going to fall back to "Send synthesized keyboard inputs" and that is nowhere near as good as "Set the contents of this text box to this unicode string" and yeah I used to work on accessibility software maybe you can tell. And how is the VM going to send data to a braille output device? Anyway, good luck with the lawsuits over arbitrarily making life harder for a bunch of members of a protected class.

One of the benefits here is supposed to be a security improvement, so let's talk about WebAuthn. I'm a big fan of WebAuthn, given that it's a multi-factor authentication mechanism that actually does a good job of protecting against phishing, but if my users are running stuff inside a VM, how do I use it? If you work at Google there's a solution, but that does mean limiting yourself to Chrome Remote Desktop (there are extremely good reasons why this isn't generally available). Microsoft have apparently just specced a mechanism for doing this over RDP, but otherwise you're left doing stuff like forwarding USB over IP, and that means that your USB WebAuthn no longer works locally. It also doesn't work for any other type of WebAuthn token, such as a bluetooth device, or an Apple TouchID sensor, or any of the Windows Hello support. If you're planning on moving to WebAuthn and also planning on moving to remote VM desktops, you're going to have a bad time.

That's the stuff that comes to mind immediately. And sure, maybe each of these issues is irrelevant to most of your users. But the actual question you need to ask is what percentage of your users will hit one or more of these, because if that's more than an insignificant percentage you'll still be staffing all the teams that dealt with hardware, handling local OS installs, worrying about lost or stolen devices, and the glorious future of just being able to stop worrying about this is going to be gone and the financial benefits you promised would appear are probably not going to work out in the same way.

A lot of this falls back to the usual story of corporate IT - understand the needs of your users and whether what you're proposing actually meets them. Almost everything I've described here is a corner case, but if your company is larger than about 20 people there's a high probability that at least one person is going to fall into at least one of these corner cases. You're going to need to spend a lot of time understanding your user population to have a real understanding of what the actual costs are here, and I haven't seen anyone do that work before trying to launch this and (inevitably) going back to just giving people actual computers.

There are alternatives! Modern IDEs tend to support SSHing out to remote hosts to perform builds there, so as long as you're ok with source code being visible on laptops you can at least shift the "I need a workstation with a bunch of CPU" problem out to the cloud. The laptops are going to need to be more expensive because they're also going to need to run more software locally, but it wouldn't surprise me if this ends up being cheaper than the full-on cloud desktop experience in most cases.

Overall, the most important thing to take into account here is that your users almost certainly have more use cases than you expect, and this sort of change is going to have direct impact on the workflow of every single one of your users. Make sure you know how much that's going to be, and take that into consideration when suggesting it'll save you money.

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5 October 2022

Dirk Eddelbuettel: RVowpalWabbit 0.0.17: Maintenance

Almost to the week one year since the last maintenance release, we can announce another maintenance release, now at version 0.0.17, of the RVowpalWabbit package. The CRAN maintainers kindly and politly pointed out that I was (cough, cough) apparently the last maintainer who had packages that set StagedInstall: no. Guilty as charged. RVowpalWabbit is one the two packages; the other one will hopefully follow shortly . And while I long suspected linking aspects to drive this (this is an old package, newer R packaging of the awesome VowpalWabbit is in rvw, I was plain wrong here. The cause was an absolute path to an included dataset, computed in an example, which then gets serialized. As Tomas Kalibera suggested, we can replace the constant with a function and all is well. So here is 0.0.17. As noted before, there is a newer package rvw based on the excellent GSoC 2018 and beyond work by Ivan Pavlov (mentored by James and myself) so if you are into VowpalWabbit from R go check it out. CRANberries provides a summary of changes to the previous version. More information is on the RVowpalWabbit page. Issues and bugreports should go to the GitHub issue tracker. If you like this or other open-source work I do, you can now sponsor me at GitHub.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

4 October 2022

Abhijith PA: Laptop refreshment

(Sorry if you have read this already, due to a tag mistake, my draft copy got published) laptop I recently bought a refurbished thinkpad x260. If you have read my post of my <a href= <!DOCTYPE html> Laptop refreshment