Cobra's bits (Posts about hardware)

Android file transfer

Cobra — Fri, 24 Dec 2021 10:32:48 GMT

My home and office computers are synchronized via the ownCloud server located at my workplace. This synchronization takes place via an TLS encrypted connection with an A+ Qualys rating. In addition, I encrypt files containing sensitive information prior to their transfer on an individual basis. Since all systems accessing this cloud folder are driven by an operating system (OS) that I trust and largely control (Archlinux), I feel very comfortable regarding the security and privacy of my data. To keep this warm and cozy feeling, I wouldn't give devices with an OS beyond my control (such as Windows, MacOS, Android, iOS) access to this folder.

Now, I fully appreciate that even a hardened desktop Linux would have difficulties to compete with the level of security offered by an up-to-date Android – with “security” being defined here in the conventional context with respect to a potential third-party adversary. But concerning the privacy of my data, and thus mine, the threat of an overly nosy first party is much more palpable. Actually, I shouldn't call it a threat. It's in fact a promise.

How, then, am I supposed to transfer or even better synchronize data from and with the newest member of my gadget zoo? Since I've acquired this gadget as a two-factor authentication for my banks, I cannot simply root it and install LineageOS without any Google services. Therefore, I won't trust the device beyond its specialized purpose and I won't give it access to my cloud folder.

But that's actually not a big deal in this case. Because of its specific function as a two-factor authenticator for my banks and several other services, the phone will remain stationary. Hence, I need to synchronize within my LAN, but not outside of it. When looking for apps that would be suitable for this task, I was initially attracted by those appealing to the nerd in me, such as, for example, croc installed (pkg install croc) and running within termux, or juiceSSH. In the end, these apps turned out to be fun for a limited time, but too tedious for everyday use. I'm very fond of controlling computers with a keyboard, but for using termux efficiently, you'd need the eyes of an eagle, the fingers of an elf and the dexterity of a spider monkey.

For ordinary human beings, syncthing is the tool of choice. It's available on f-droid, easy to set up on all participating systems, and works reliably without manual intervention. In my case, I've simply created a folder (~/androidshare) on my desktop that automatically receives all files from my phone that may be worth to keep, including the backups of the andOTP and keepassDX databases and all photographs of my cats. 😍

Maxi

Cobra — Sun, 26 Sep 2021 12:45:37 GMT

I've retired my veteran netbook Mini after 10 years of service and 7 generations of Debian in 2018. The SSD was becoming corrupted, and in view of its low performance and advanced age, I decided that it wouldn't be worth the time and money needed to replace it.

In the meantime, I've been using the Fujitsu Lifebook I acquired in 2011. As a matter of fact, I gradually used this low-end notebook in favor of my desktop until I was basically working exclusively with it. From March 2020, I've used it day in, day out. During this time, it became painfully obvious that the lifebook's performance is no longer adequate for my needs. About a year ago, I've thus started to look for a successor, but considering my recent change in preference, I was looking for a notebook with higher performance and display resolution, as well as a backlit keyboard.

There were several contenders, all armed with processors of the Cezanne series of AMD. But my favorite was the Ideapad 5 Pro 16 because of its comparatively large screen real estate with a WQHD resolution and 16:10 form factor. When it was offered for €899 by Lenovo in a bargain sale, I didn't hesitate to accept the offer.

The Ideapad 5 Pro 16 comes with a gun-metal grey (“storm grey”) metal case with an excellent finish. Despite its slightly larger display diagonal, it is significantly smaller, lighter, and, particularly, thinner than my Lifebook. At the same time, it leaves it light years behind in terms of performance:

Fujitsu Lifebook AH530

Lenovo IdeaPad 5 Pro 16ACH6

Processor

Intel P6200

AMD Ryzen 7 5800H

Lithography (nm)

32

7

Frequency (GHz)

2.13

3.2–4.4

L2/L3 cache (MB)

0.5/3

4/16

# cores/threads

2/2

8/16

Weight (kg)

2.5

1.9

Display (inch)

15.6 (1366×768)

16 (2560×1600)

RAM (GB)

4 (DDR3-1066)

16 (DDR4-3200)

Mass storage (GB)

500 (SATA HDD)

1000 (PCIe SSD)

TDP (W)

35

45

Battery life (h)

3

8

iperf (Mbit/s)

40

360

Cinebench R23

336/641

1445/12969

hdparm -t (MB/s)

70

2300

Price (€)

299

899

	Fujitsu Lifebook AH530	Lenovo IdeaPad 5 Pro 16ACH6
Processor	Intel P6200	AMD Ryzen 7 5800H
Lithography (nm)	32	7
Frequency (GHz)	2.13	3.2–4.4
L2/L3 cache (MB)	0.5/3	4/16
# cores/threads	2/2	8/16
Weight (kg)	2.5	1.9
Display (inch)	15.6 (1366×768)	16 (2560×1600)
RAM (GB)	4 (DDR3-1066)	16 (DDR4-3200)
Mass storage (GB)	500 (SATA HDD)	1000 (PCIe SSD)
TDP (W)	35	45
Battery life (h)	3	8
iperf (Mbit/s)	40	360
Cinebench R23	336/641	1445/12969
hdparm -t (MB/s)	70	2300
Price (€)	299	899

For comparison, my 9 years old desktop achieves 820/3650 points in the Cinebench R23 single/multi benchmark, and Dell's 17″ high-end notebook XPS 17 in a comparable configuration (processor graphics, 16 GB RAM, 1 TB SSD, 2.2 kg) with an Intel® Core™ i5-11400H for €2098.99 (1920×1200 non-glare) or €2398.99 (3840×2400 glare) scores 1467/9017 points according to c't 21/2021.

There wasn't any question about the Linux distribution I would install on the Ideapad (Arch, of course), but I debated with myself whether I should install a desktop or stay with Openbox as on all my other systems. In view of the medium-high display resolution of 189 ppi, I finally settled for Budgie, a Gnome-based desktop known for its gracious handling of high-dpi displays. And so far I like what I see: the desktop has an unobtrusive, rational, and no-nonsense quality about it.

The Ideapad is officially specified to have an Intel AX200 wifi chip, which works perfectly under Linux. But I had been warned by posts in the interwebs that it may instead be delivered with a Realtek RTL8852AE chipset, which is not yet supported. And that's what happened of course also in my case. I thus installed over a LAN connection (using an USB/ethernet adapter) and installed the driver for the 8852 provided on the AUR right after. The driver works fine except when the notebook goes into hibernation, after which there's no wifi device any more – it simply vanishes. I haven't found a solution for this inconvenience, but hope that the official support of the rtw89 driver by the mainline kernel will solve this issue, and will hopefully materialize with Linux 5.15. Alternatively, I could replace the wifi module as others have done.

Other than that, everything works as intended, and lightning fast.😂 Oh, I've replaced pulseaudio by pipewire-pulse to use my bluetooth headset, which would otherwise be without microphone. And I've installed rofi, which I still prefer as a program launcher over anything a desktop can offer...

Resistance is futile

Cobra — Sat, 28 Aug 2021 14:37:38 GMT

In my childhood, I lived in conditions that would be considered poverty today, but were not uncommon at the time. For example, our apartment featured neither a toilet nor a bathroom or shower. The toilet was located half a floor down in the stairway, and we shared it with our neighbors. To take a bath instead of a quick wash, we had to visit the public bath. The stove was still coal-powered, and we relied on it for cooking and getting hot water for preparing coffee and tea as well as for washing dishes. In the winter, this stove was also used for heating, but the heat didn't spread far, and we had to put on several layers of clothing in the other rooms. As we had no place for a washing machine, the clothes had to be carried to the next laundromat once per week.

But we felt very comfortable, even privileged, since we enjoyed a number of household appliances that were not entirely obvious at this time. For example, we had a telephone, a huge table-top radio, and even a black-and-white cathode ray television set (which, I remember, was smaller than the radio) with three programs that signed-off at midnight. Plenty of entertainment for my parents, but I had lots of toys in addition, of course. And since my parents tried very hard to make me happy, I got the greatest gifts a boy could wish for at that time: a Märklin model railway and a Carrera slot-car race track.

Much to their disappointment, these electric gadgets held no fascination for me. I actually spent most of my spare time outside, playing soccer and swimming, and indoors I much preferred classic board games such as Mills and Checkers, and later Chess, which became kind of an obsession and occupied most of my time and attention in solitary concentration. To get me back to a social life, my parents very cleverly introduced me to classic card games, which I then started to study with three equally nerdy friends of mine. We played Rummy, Canasta, Whist and Bridge, but also the German classics Skat, Schafkopf, and Doppelkopf.

I've recently googled for these three friends, and found to my great delight that they have all made their way. A surgeon, an attorney, an engineer – and I became a physicist instead of an electrician, as my parents had planned. And I hope that for them the ability to play a variety of board and card games has been proven to be as useful as it has been for me. For example, when I arrived in Japan some 15 years later for my postdoctoral studies, I went to an English pub I knew from a conference after realizing how fundamentaly lonely I was. The time was early, long before it actually opened, but there was a girl behind the counter, waiting for the first guests, playing Backgammon with herself. It was my knowledge of Backgammon acquired 15 years ago that enabled me to play with her, earning me an invitation for a party where I would meet Susie from Kenya. But that's another story.😙

Nowadays, I keep an average household with regard to technology. It features all of the typical electrical appliances of western civilization, sprinkled with plenty of electronic gadgets, such as desktops, notebooks, tablets, e-book readers, and even a mobile phone, but it's not “smart”. In fact, so far I even didn't bother myself with a smartphone, as I didn't see any compelling reason for using a technology without having the slightest need for it. Worse, it seems that all gadgets with the attribute "smart" are essentially designed to collect as much data as possible about their unsuspecting, dumb users and send that data to various third parties who subsequently profit from it. And last but not least, I feel thoroughly repelled by the pathetic addiction of users to their smartphone, made evident by the innumerable smombies and nomophobes whose catatonic behavior I have to endure every day.

The first of these circumstances has changed very recently. In complying to the revised payment services directive of the EU, one of my banks has decided to terminate mTANs as a method of payment authorization. As alternative, they very prominently advertise an app-based authorization, although a photoTAN generator is in principle also available – but of course not compatible with any other bank. Should I pile up photoTAN generators on my desk or go for the smartphone? I pondered this question for a short time, but it was finally decided by unexpected circumstances turning up in an entirely different context: traveling in the age of the pandemic. My wife has important family business in Japan, and for her entry and the subsequent 14 days of quarantine, she will need no fewer than three apps on a smartphone, which can be either her own one, or has to be rented at the airport.

In view of this development, an attitude of denial would be donquixotesque. I decided that we would instead try to embrace the situation, and make the best out of the gadgets we are forced to acquire by circumstances. That shouldn't be too difficult, since I already knew from my experience with our Nexie that an Android device with small form factor can be great fun. However, there was no need to spend the obscene amounts of money the smartphone industry has somehow managed to establish, with price tags for the flagship phones having tripled over the last decade. Chapeau to the industry for the masterful creation of a new consumers desire leading to excessive debts particularly for the young generation. I'm quite immune to this attempt of seduction, and we consequently decided to look into the low- rather than the high-end.

Since I would be using my phone for security-critical tasks, the main criterion was the guaranteed availability of updates, which is the domain of the Google Pixel phones, a few of the top models from other manufacturers, and of phones running Android One, of which only the Nokias are left. After looking through the specifications, I settled on a Nokia 3.4, which seemed more than sufficient for the simple tasks I would need it for. For my wife, who will certainly enjoy playing an occasional game on her phone, I looked for a higher-class SoC than on the Nokia, and finally opted for the Motorola Moto G30. Both smartphones together came for less than €300, the maximum amount I had been willing to spend.

And you know what: I wouldn't have half of the fun with this little gadget if it hadn't been so affordable. I was a bit disappointed that the Android 11 upgrade didn't come earlier, but eventually it came, and the phone is currently running Android 11 with the latest patches (August 5). That's good enough for me to use it for the purpose I bought it for, i.e., as an authentication factor for my banks. But I also set it up as a general two-factor authentication device by installing and configuring andOTP for some of my most important accounts, such as the control panel of the server running this blog. Being thus an integral part of my security measures, it will securely stay at home, where it has already plenty of alternative uses. Here's one of them: I always wanted to have an HP 48, but never got it. Now I have one!

New Neuland

Cobra — Sat, 08 May 2021 17:11:15 GMT

In 1994, snafu.de provided my first home connection to the interwebs via a 33.6K (kbits/s) modem. The upgrade to 56K came only a year later, but being a speed freak, I soon abandoned snafu for the German telecom who offered ISDN (128K by channel bonding) and again one year later the first ADSL with 768K. Just two years later again the German telecom managed to piss me off so thoroughly that I quit them right away. I selected QSC as my post-Telekom provider, which was such a lucky choice that I stayed with them almost 20 years, starting with the symmetric 2 Mbit/s SDLS line in 2002 and upgrading to the mainstream ADSL2+ option in 2008. Compared to where we had been just a decade before, the speed offered by this technology was hardly believable. In 2021, however, the speed is lamentable. The upload of 1 Mbit/s is a liability in the time of daily video conferences, and the download of 16 Mbit/s is sorely testing my wife's patience during the many hours it takes to download an eagerly awaited and freshly purchased video game.

It's high time to upgrade, I told myself, and consequently looked at the options available to someone living more or less in the center of the western part of Berlin. I had entertained the hope that when upgrading my connection, FTTH would be available, but as the matter stands the only affordable option is still VDSL. After my experiences with the Telekom, I was reluctant to again enter a relation with them, but I'm not too fond of the other big players (Vodafone, 1&1, O2) either. Fortunately, I've talked to my colleague Jonas about my plans, and he recommended easybell, a small regional provider with a clear focus on customer service. I very much liked what I saw and ordered their super-vectoring VDSL offering 250 Mbit/s down and 40 Mbit/s up. The whole procedure was transparent and very well documented, and the handover went as smoothly as possible: we got disconnected at 15:00, and when I finished setting up the new router at 15:30, it connected right away.

Woohoo! Now we're talking. 😎

The new router is a Fritz!Box 7590, and since its producer AVM is also located in Berlin, my internet connection is now a purely regional one. 😉 The 7590 does not support IEEE 802.11ax or Wi-Fi 6, which doesn't really matter for me since I don't have a single device that would support this standard. However, compared to the Fritz!Box 7170 I had before, the increase in wireless speed is impressive, much larger than I had expected. On my ten years old Fujitsu Lifebook, I never saw anything better than 10 Mbit/s with the 7170, but I'm getting a very stable 40 Mbit/s with the 7590. Makes a huge difference when using Mathematica via ssh -Y -C to my desktop: while the interface reacted sluggishly before, it's now downright snappy.

Alas, not all of my devices can actually benefit from the new and shiny wifi: my Nexie won't connect to it, and constitutes the collateral damage of this modernization. Debugging the attempts to connect returned the error message NETWORK_SELECTION_DISABLED_ASSOCIATION_REJECTION, which is caused by the activated “Protected Management Frames” for the login process (on the Fritz!Box: "Unterstützung für geschützte Anmeldungen von WLAN-Geräten (PMF) aktivieren"). Since this feature is required for WPA3 and thus the protection of my entire wireless network, I'm not willing to sacrifice it for one nine years old tablet, even when this tablet happens to be my beloved Nexie. Still, I will miss it, particularly since tablets with this diminutive size have been replaced entirely by phablets, and are not produced any more. And before you're going to argue like 'so-why-not-buying-such-a-phablet': I did exactly that, although for an entirely different reason, which I will disclose in a subsequent post.

Fast, faster, M1?

Cobra — Thu, 31 Dec 2020 14:36:24 GMT

I should have created a category called “Modern advertisement techniques” or “How-the-media-manipulate-us-to-help-Apple-selling-its-products”. The crude attempts of the tabloid press are so glaringly obvious to anybody that they are more amusing than anything else. What I find far more disconcerting is the subtle approach one encounters in media of higher standard. At first the occasional inaccuracy or omission seems innocuous enough, but after a while it becomes clear that all of these apparent oversights and mishaps are invariably in favor of Apple, establishing an act of framing, deliberate or not. Here is one and here is another example of what I'm talking about.

Now, in June Apple announced that they are going to switch from Intel to ARM, and in November they announced the Apple M1 system-on-chip with their usual vastly exaggerated grandiose claims (3×, 6×, 15× faster!!!). One doesn't have to be the oracle of Delphi to predict the resulting media circus and the ever higher flying expectations based on nothing but hype.

Finally, some meaningful benchmarks (Cinebench R23) in c't 26/2020. Before examining and evaluating the numbers, here are two quotes from this issue:

p. 36 (Bit-Rauschen) Beim 15-W-Typ Ryzen 5000U wird es jedenfalls spannend, ob er zumindest bei Multithreading Apples-ARM-Renner M1 einholt und somit die x86-Ehre rettet.

p. 44 (Alles M1!) In der Single-Core-Performance enteilt der aktiv gekühlte M1 [...] allen bisherigen Mobilprozessoren der 15- bis 45-Watt-Klasse [...]. In der Multi-Core-Wertung sortiert er sich zwischen den 45-Watt-Mobil-CPUs Core i7-10750H (6300 Punkte) und Ryzen5 4600H (8370 Punkte) ein [...].

Now, these statements very clearly imply that the performance of the M1 surpasses that of any currently available 15-W mobile processor, wouldn't you say so?

Let's compare the single/multithreaded Cinebench R23 scores [1] of Intel's TigerLake top model and three Ryzen 7 4000U with those of the M1:

i7-1185G7               1538/6264
4700U                   1184(1218)/6874(7269)
M1                      1514(1517)/7760(7786)
4750U                   1184/8088
4800U                   1235/10156

As you can see, Apple has come up with a highly competitive chip offering a single-core performance on par with the 1185G7, and a multi-core performance just between the 4700U and the 4750U. But neither do we need a 45-W-CPU, nor the upcoming Ryzen 5000U to leave the M1 far behind in terms of multi-core performance: the 4800U does that well enough. And that's what I would have liked to read in an objective summary of the M1 instead of the distorted statements above.

The M1 is the first ARM-based processor that offers competitive performance for desktop applications. Is that the end of Intel and AMD? The loss of Apple as a major client may seem like an enormous loss for Intel, but actually it's a rather insignificant one, and some even believe it to be beneficial for them. Moreover, the M1 currently only runs on Apple hard- and software, resulting in a correspondingly small market share. More alarming, particularly for AMD with their hopes to break the dominance of Intel processors in data center and high-performance computing applications, is the current development of ARM-based server processors offering high performance for an affordable price. Remember when Linux-based x86 boxes replaced SPARC, MIPS, PA-RISC, and Power PC workstations running Solaris, IRIX, HP-UX, and AIX? That's just 11 years ago. Perhaps we are witnessing an analogous transition right now.

[1] A very similar comparison can be found, by the way, in the current issue of c't (Apfel-Alternativen, c't 1/2021, p.109). The values here are taken from cpu-monkey.com, and the ones in parentheses are from c't. If you have an older processor and would like to compare, chances are good that you find it in the comprehensive, community-compiled list at computerbase.de.

Using Nexie

Cobra — Sat, 27 Jun 2020 16:19:14 GMT

About a year ago I described the successful reanimation (Saving Nexie) of our Nexus 7 from 2012 by installing LineageOS on it. We were very happy with the result, and the little gadget subsequently accompanied my wife on her trip to Japan last year. But when she returned, Nexie seemed to disintegrate: the display and the backside started to separate for no apparent reason, and nothing could keep them together.

We thought that Nexie got somehow damaged during the trip, but I anyway asked our lab McGyver for help. She carefully dissected it and discovered that the culprit is the battery, having turned from a flat sheet to something resembling a Fugu. I purchased a new one, with which the display again connected to the back with a satisfying >click<. 😌

I brought the fully intact Nexie home and proudly presented it to my wife. She was unusually timid and finally told me that she wouldn't know what she should use it for. In fact, the Nexie doesn't really have a place anymore in her gadget zoo that includes an up-to-date Android tablet as well as a Windows 10 detachable. She thus tried to motivate me to take care of the Nexie, and despite my vow that I won't have anything to do with Android or iOS gadgets, I finally gave in and promised to give it a try.

My first Android device! A new world to be discovered! 😋

It turned out to be rather straightforward to switch accounts on an Android device, and to throw out old apps in the favor of new ones. And although I do realize of course that the Nexie is very slow by modern standards, I find it perfectly adequate for the simple things I use it for (mostly checking the weather, the soccer results, and the ticker, as well as reading the books that are too much for my old e-book reader and watching an occasional video). Thanks to Blokada from the F-Droid Store, all apps are free of ads of any kind. And despite the humble hardware, I stand no chance when playing Chess against the Nexie.😶

I haven't posted any screenshots for ages, so here are two showing Nexie in its full glory:

If you don't see anything: these are the first images in this blog in WEBP format, which results in images of essentially the same quality as the original PNG at a third of the size. I will use this format for all future images and also retroactively, so update your browser (that will probably work soon even on a Mac).

Upgrade to Windows 10

Cobra — Fri, 13 Dec 2019 16:47:57 GMT

My wife's gaming rig is still running on Windows 7, and it's about time to change that. In principle, an upgrade to Windows 10 requires only the download of the Media Creation Tool from Microsoft on the system to be upgraded. However, to save myself the download of several GB of data with my meager DSL connection at home, I've used this tool in my virtual Windows 7 at the office to prepare a USB stick for installation. It took some time to find an active download link for the USB 3.0 drivers compatible with VirtualBox (Intel 7 Series C216 Chipset Family, which Intel has discontinued), but in the end I had my stick.

After uninstalling the antivirus scanner (Avast), I've plugged in the stick, clicked on setup.exe, and off it went. But after 15% installation progress:

Error: 0x8007025D-0x2000C
The installation failed in the SAFE_OS phase with an error during APPLY_IMAGE operation.

Just below the error message is a link that can neither be clicked nor copied. Now that's usability! In any case, the suggestions on this page aren't helpful at all, but send the users experiencing this error message on the wrong track. Fortunately, third-party pages such as techjourney and the windows club do much better in this respect, in that they have the most likely reason on top of their list: corrupted installation media. And in fact, when I simply let the Media Creation Tool download the files, the upgrade works flawlessly. Didn't even take 3 h including the download, which was much faster then I had expected.

You see how easy the upgrade is – even for someone who hasn't actively used Windows since 15 years. Don't be one of these pathetic figures that are eternally whining and bawling that they have a god-given right to use Windows XYZ until the end of the time, and are very loudly expressing the opinion that Microsoft must be condemned by international (or at least European) law to keep the OS in question alive. Get a grip on yourself, make an update, and deal with it, for Pete's sake. Or switch to OpenBSD or any other one of these geekish systems. You could also buy a Mac, if you insist. But don't act like a newborn.

For us, Windows 10 itself is not entirely new, since earlier this year, we purchased a Lenovo Miix 630 for accompanying my wife on her trip to Japan. We got this 'Windows on ARM' detachable for €444 complete with a back-lit type cover and a pen, 8 GB of RAM, and LTE, allowing her to access the internet from home without the need to search for places offering public wifi. The Miix turned out to be very versatile and fun to use, and it has an almost unbelievable battery life in excess of 20 h thanks to its Snapdragon 835 processor (a mid-range smartphone SOC). What I also like is the rolling-release concept of Windows 10, which guarantees that the device isn't obsolete after at most three years as it's custom for Android gadgets. It's a pity that this interesting concept is so unpopular. Lenovo has already stopped the production of the Miix, and there aren't any others like it (the Surface Pro X from Microsoft comes at more than three times the price).

Saving Nexie

Cobra — Sun, 28 Apr 2019 10:01:57 GMT

We own a first generation Nexus 7 from 2012, which my wife affectionately calls Nexie because of its compact form factor. It impressed me with its high build quality, particularly considering its modest price point of €199. It's performance was more than satisfactory with the stock Android 4.1, but when it got updated to Android 5.1 in 2015, it was reduced to an unresponsive brick, no matter what I've tried (including a factory reset). We finally decided to retire it and to use it as a, well, wall clock. But recently, the time on the Nexus was often running slow by more than an hour. The reason were resource-intensive background processes updating the various Google apps installed by default.

Can we resurrect the Nexus by flashing it with an alternative ROM such as LineageOS? That's at least what I'm going to try. Note that I'm fairly ignorant with respect to Android and its devices. But anyway, let's get going.

1st step

I search the web for “Nexus 7 (2012) LineageOS”. To my relief, there's general agreement that our Nexus can run LineageOS 14.1, corresponding to Android 7.1. I thus download the image for our (GSM free) version of the Nexus 7. I also find some instructions regarding the installation. I learn from them that I have the option to install the Google Apps (particularly the play store) or not.

2nd step

I'm in favor of installing a pure LineageOS system free of Google Apps, and to use F-Droid instead of the Google play store, but my wife pleads for the latter. Since she's the primary user, I look at the options on OpenGapps and download the pico build for ARM 32 bit, Android 7.1.

3rd step

To install the custom ROM and the Google Apps, I need a custom recovery image such as the one provided by TWRP. I download the latest version for my Nexus.

4th step

Prepare your device, they say. All right, I tap the 'Build Number' under 'About Phone' in 'Settings' seven times and thus become a developer (not a joke, it really works that way 😲). I then scroll down and enable USB debugging.

5th step

The instructions mention the commands adb and fastboot, which I find to be contained in the package android-tools. I thus install these tools on my Fujitsu Lifebook:

sudo pacman -S android-tools

6th step

I use the USB cable of my Kobo reader (a conventional microUSB-to-USB cable) to connect the Nexus to my Lifebook, and chose MTP in the USB dialog on the Nexus.

7th step

All right, now it comes. (On hindsight, I could certainly do better when I would try a second time. But anyway: it worked. 😎)

# adb reboot bootloader

Yup, the Nexus boots and is now in a kind of repair mode. 😊

Now as root:

$ fastboot oem unlock
$ fastboot flash recovery twrp-3.3.0-0-grouper.img

A subsequent 'adb reboot bootloader' doesn't work (I now believe that 'fastboot reboot' would have). I reboot the Nexus manually by navigating with the volume and power keys. I then switch in the same way to recovery mode, upon which TWRP starts up.

# adb push /home/cobra/Downloads/lineage-14.1-20171122_224807-UNOFFICIAL-aaopt-grouper.zip /sdcard/
# adb push /home/cobra/Downloads/open_gapps-arm-7.1-pico-20190426.zip /sdcard/

Next, as found in the instructions, I navigate in TWRP to the Wipe menu. For some reason, wiping fails, and I'm stuck in a boot loop. 😨

I search the web and find that boot loops are rather common. A recommended solution is to either erase or format the userdata:

$ fastboot erase userdata
$ fastboot format userdata

but that doesn't do anything (just telling me that it's <waiting for device>). Only after I hold power/volumedown for 10 s, I see the repair menu, and when going to recovery mode, TWRP seems to finish what it has tried to do. pooh

I have no idea what went wrong there, nor precisely how it was corrected. But I found one statement in the web that gave me courage: “as long as your device does anything when switching it on, it is NOT bricked.”

The rest is easy: I go to install, select LineageOS and Google Apps, install and reboot.

The result

Much better than I had hoped for. The interface reacts instantaneously, animations run smoothly, and apps start fast. It feels as good as new. Well, my wife says: even better. ☺

Modern file compression

Cobra — Sun, 10 Feb 2019 13:17:49 GMT

Unknown to most users, file compression silently works behind the scene. Updates for any operating system, for example, are compressed. That happens automatically and the user doesn't even need to know about it.

But sometimes, we have a choice. In Archlinux, for example, we can set the compression we'd like to use for packages created by makepkg (such as those installed over the AUR) – but how to chose between gz, bz2, xz, lrz, lzo, and z? And some backup software adds further options: Borg, for example, offers zlib, lzma, lz4, and zstd.

Most surprisingly, some of these algorithms have been developed only very recently: zstd comes from Facebook (2016), and there's brotli from Google (2015) and lzfse from Apple (2015). Why do these multi-billion-dollar companies develop compression algorithms? Because of the multi-billion dollars.

Instead of testing each of these algorithms yourself, you can use lzbench. It tests all open source algorithms of the lz family with the de facto standard file package in the compression business, the silesia suite.

Here are three examples geared toward high compression ratio, high speed compression, and high speed decompression:

High compression ratio (<25%)

➜  lzbench -c -ebrotli,11/xz,6,9/zstd,22 silesia.tar
lzbench 1.7.3 (64-bit Linux)   Assembled by P.Skibinski
Compressor name         Compress. Decompress. Compr. size  Ratio
memcpy                   9814 MB/s  9852 MB/s   211947520 100.00
brotli 2017-12-12 -11    0.48 MB/s   385 MB/s    51136654  24.13
xz 5.2.3 -6              2.30 MB/s    74 MB/s    48745306  23.00
zstd 1.3.3 -22           2.30 MB/s   600 MB/s    52845025  24.93

These are single core values. xz compression (but not decompression) profits from multithreading, while brotli and zstd do not.

High speed compression (for compression ratios <50%)

➜  lzbench -c -elz4/lzo1x silesia.tar
Compressor name         Compress. Decompress. Compr. size  Ratio
memcpy                   9861 MB/s  9768 MB/s   211947520 100.00
lz4 1.8.0                 524 MB/s  2403 MB/s   100880800  47.60
lzo1x 2.09 -12            521 MB/s   738 MB/s   103238859  48.71

High speed decompression (> 2000 MB/s)

↪ lzbench -c -elz4/lizard,10/lzsse8,6 silesia.tar
Compressor name         Compress. Decompress. Compr. size  Ratio
memcpy                   9579 MB/s 10185 MB/s   211947520 100.00
lz4 1.8.0                 525 MB/s  2421 MB/s   100880800  47.60
lizard 1.0 -10            421 MB/s  2115 MB/s   103402971  48.79
lzsse8 2016-05-14 -6     8.25 MB/s  3359 MB/s    75469717  35.61

What do we learn from these benchmarks?

If we want high compression reasonably fast, nothing beats xz. It's just perfect for what it's actually used by some (all?) Linux distributions: to distribute updates with acceptable computational resources over a channel with a very limited band width.
If the distributor commands over virtually unlimited resources, and compression speed is thus not an issue, brotli and zstd are clearly superior to all other choices. That's how we would like to have our updates: small and fast to decompress.
If size is not of primary importance, but compression speed is, lz4 and lzo are the champions.
If decompression speed is essential, lzsse8 wins. This is a lesser known member of the lz family and not widely available, in contrast to lz4 which thus scores again.

Debian 9

Cobra — Mon, 19 Jun 2017 18:53:12 GMT

Stretch is stable. Testing is now called Buster.

sed -i 's/stretch/buster/g' /etc/apt/sources.list

I could equally well just use 'testing', but for some presumably deeply rooted psychological reasons, I like the codenames better.

For my veteran netbook mini, buster is now the 7th incarnation of Debian or Debian-derivatives in its 9 years of operation: Etch, Lenny, Squeeze, Wheezy, Jessie, Stretch, Buster. I'm sure it will also run Bullseye. 😉