605 private links
I just realized why my plays keep re-running roles when running a certain role.
It is because I have dutifully replicated the same parameters used in the play for each role in the dependencies list, which includes the tags parameter.
So when I call the play with --tags R, the R role (which is tagged eponymously) triggers, but also any role in the play which lists R in its dependencies, because I tagged the dependencies!
The solution is obvious and I am embarrassed it has taking me so long to realize: do not tag roles in the dependencies list!
Considered because I was trying to answer the question:
Can we use a different R version per directory/project?
With my R role it has been easy to maintain multiple different R versions on a server. But I have not really been able to pick-and-choose which R version to use with any particular project since there was only one version symlinked globally (/usr/local/bin/R -> ...).
Could we not set a different version locally, in a particular R project?
- https://github.com/r-lib/rig - this would do it, but does much more than I want, would interfere with my Ansible role
- https://www.monicathieu.com/posts/2024-05-21-multiple-r-versions.html
- https://support.posit.co/hc/en-us/articles/200486138-Changing-R-versions-for-the-RStudio-Desktop-IDE -
export RSTUDIO_WHICH_R=/usr/local/bin/R - https://github.com/vubiostat/Renv - good, but last commit 13 yrs ago
- https://direnv.net - this probably fits the bill
- https://github.com/hyperupcall/autoenv - similar to
direnvbut smaller in scope - https://github.com/jdx/mise - direnv, make and asdf all in one tool https://news.ycombinator.com/item?id=34583080
- https://github.com/untitaker/quickenv - like
direnvbut less intrusive, more light-weight - https://asdf-vm.com
- https://modules.sourceforge.net - Environment Modules, the OG in this space
apt install modules - https://github.com/TACC/Lmod - LMod, this is what's used by UPPMAX
asdf
After reading about it a little, I get the feeling it would be more cumbersome than direnv.
I am not sure I understood correctly, but sounds like the R plugin actually wants to manage the
entire R installation (essentially what rig does).
- https://github.com/asdf-vm/asdf
- https://asdf-vm.com/guide/introduction.html
- https://github.com/asdf-community/asdf-r - community plugin for R
direnv
I cannot find anyone talking about direnv with R on the web. Weird.
- https://direnv.net/#man/direnv.1
- https://direnv.net/#man/direnv-stdlib.1
- https://perrotta.dev/2022/01/direnv-automate-your-environment-variables
- https://rnorth.org/practical-direnv
- https://rnorth.org/more-practical-direnv
- https://pinnsg.com/direnv-take-control-of-your-development-environment
- https://www.digitalocean.com/community/tutorials/how-to-manage-python-with-pyenv-and-direnv
- https://shivamarora.medium.com/a-guide-to-manage-your-environment-variables-in-a-better-way-using-direnv-2c1cd475c8e
- https://platfrastructure.life/post/direnv
- https://github.com/direnv/direnv/issues/73 - some quite interesting example code here
- https://thelinuxcode.com/managing-per-directory-environment-variables-effortlessly-with-direnv
[So what I want] is a "shim" binary that dispatch to the desired binary
https://mise.jdx.dev/dev-tools/shims.htmlThe
.envrcfile is treated like a shell script, where you can also list arbitrary
shell commands that you want to be executed when you enter a project directory.
http://rednafi.com/misc/direnv/#why-envrc-file-and-not-just-a-plain-env-file
My direnv example
Machine in question is Ubuntu 22.04 x64.
$ apt install direnv
$ printf 'if hash direnv >/dev/null 2>&1; then\n eval \"$(direnv hook bash)\"\nfi' >> ~/.bashrcIn the R project directory, I created a subdirectory bin (for convenience) and created a symlink to the R binary I wanted, naming it R. Also added this subdirectory to .gitignore (and .Rbuildignore if it's an R package).
In the package directory I created .envrc containing simply:
PATH_add binAnd enabled with direnv allow the first time I cd into the directory.
Now the R command defined in bin successfully overrides the system-wide command:
$ ls -l `which R`
lrwxrwxrwx 1 taha taha 18 maj 3 21:47 /media/bay/R/periodicdata/bin/R -> /opt/R/4.5.0/bin/RNote that this works in the terminal. I am pretty sure we will need to do more to have IDEs such as RStudio Server or Codium Server take heed on a per-directory basis. Will investigate further as time permits.
Support for direnv in RStudio Server, Codium, et al.
code-server just works. Well, except for the "Attach R" button, which still only uses the system-wide R binary.
VSCodium would have worked, except I installed and configured direnv on the server, and VSCodium runs on my desktop. Expected, and easily fixed by installing and configuring direnv on the desktop too, if desired.
VSCodium with the Remote SSH plugin. It's complicated. Seems the languageserver component (which the VSCodium R plugin uses) sees the system-wide R binary, despite definitely picking up on the directory-specific renv.
And the VSCodium "Attach R" button (in the statusbar) works but attaches the system-wide R binary. But running R in the built-in terminal respects our direnv config.
RStudio Server fares similarly, in that the built-in terminal behaves like any terminal and respects our direnv config, but the built-in "R Console" does not, and neither do the other built-in buttons etc. But it feels worse because a lot of stuff will automatically run in the Console and thus use the wrong R version. Unfortunately Posit still to this day lock their "multiple versions of R" functionality behind a "Pro" license.
I guess one (really ugly) work-around would be to run multiple RStudio Server instances, each with a hard-coded R version: export RSTUDIO_WHICH_R=.... For R package development it's primarily R-release and R-devel that matters, so it's not unworkable. And I have been known to run multiple instances anyway (one per LXC container).
More links and notes
- https://github.com/rstudio/renv/issues/254 - How to deal with different versions of R?
- https://stackoverflow.com/questions/63291613/how-to-set-r-version-in-rproj-file - that's not possible
- https://support.posit.co/hc/en-us/articles/200486138-Changing-R-versions-for-the-RStudio-Desktop-IDE
R versions
At present 2025-05-03:
- R-devel is NA
- R-patched is NA
- R-release is 4.5.0
- R-oldrel is 4.4.3
This is best determined using the rversions:: package!
Here is how to highlight the string noodles in the output of tail -f using grep:
tail -f /var/log/auth.log | grep --line-buffered --color=always -e "^" -e "noodles"Figured it out quickly thanks to these posts:
- https://superuser.com/a/1192944
- https://stackoverflow.com/a/7162898/1198249
- https://stackoverflow.com/a/23395752/1198249
There is also other (possibly better) ways to accomplish the same effect:
With Python, you can just open a shell and quickly try out some code in a so-called REPL console. Guess what, you can do the same with Ansible. Browse your inventory, and even remote file systems in an interactive shell with
ansible-console.
If you have installed Ansible via pip you already have this nifty tool installed.
Thanks to git log -1 it is trivial to view the latest commit in a repo, and combined with find ... -exec ... we can easily do that for multiple repos at once (for example see my commits bash function).
Turns out doing the same for the earliest commit in each repo is not at all trivial. Here is my approach (it should be said up-front that it's not pretty). But I wanted to get a handle on when I started working on some repos, and this pulled out the data I needed without having to do it manually for each individual repo.
taha@asks2:/media/bay/taha/projects/ansible/pub/roles
$ find . -maxdepth 2 -name ".git" -exec sh -c "git -C {} --no-pager log --all --pretty=format:\"%cs %h%d %s [%cn]\" | tail -n1" \; -exec printf " %s\n" {} \; | sort -n
2021-03-14 02506d4 Initial commit [taha] ./texlive/.git
2021-03-14 14ddd9a Initial commit [taha] ./desktop-tools/.git
2021-03-14 2bfe5bc Initial commit [taha] ./R/.git
2021-03-15 0c2deda Initial commit [taha] ./calibre-web/.git
2021-04-02 7a2bdb2 Initial commit [taha] ./iriun-webcam/.git
2021-04-13 167ef2d First commit [taha@asks2] ./shaarli/.git
2021-05-28 ca70e06 Initial commit [taha] ./wallabag/.git
2021-06-09 3d4891e Initial commit [taha] ./lxd-server/.gitThe directory roles contains a bunch of git repos (and possibly also a few folders that are not repos, which we exclude from find with -name ".git". Then for each repo, we list all commits (across all branches) using a custom format but then, importantly, only showing the last one which is the earliest commit.
To be able to tail this git command (and not the entire find command) we need to put it inside sh -c ....
Then we use a second exec statement to append the current directory name (so we can orient ourselves in the output) and then sort the entirety on the output (which thanks to our custom git format lists the commit date in the first column). Note that piping strips the colour from the git output, so no need to set colours in our pretty-format.
- https://stackoverflow.com/questions/51376361/getting-commit-history-from-multiple-repositories-for-some-period
- https://stackoverflow.com/questions/5188914/how-to-show-the-first-commit-by-git-log (this approach with
git rev-list --max-parentsdid not work in my case, not sure why) - https://andrewrea.co.uk/posts/git-log-over-multiple-repos
- https://stackoverflow.com/questions/50882822/view-logs-of-multiple-git-repositories
- https://stackoverflow.com/questions/6712423/how-do-i-count-the-number-of-commits-made-in-to-all-repos-hosted-by-gitosis-on-m
- https://stackoverflow.com/questions/49388069/what-does-git-log-1-do
- https://stackoverflow.com/questions/307015/how-do-i-include-a-pipe-in-my-linux-find-exec-command
- https://stackoverflow.com/questions/1371261/get-current-directory-or-folder-name-without-the-full-path
Let's say you are looking for old Ansible code dealing with multiple distros (meaning multiple files in the ./vars/ directory) to draw inspiration from. How can we quickly identify the roles with vars directories containing more than a single file?
$ cd /media/bay/taha/projects/ansible && find . -not -path "*/archived/*" -not -path "*/testing/*" -path "*/vars/*" -printf "%h\n" | sort | uniq -d && cd $OLDPWD
./pub/roles/apache/vars
./pub/roles/common-systools/vars
./pub/roles/desktop-environment/vars
./pub/roles/digikam/vars
./pub/roles/graphics-driver-nvidia/vars
./pub/roles/php/vars
./pub/roles/php-versions/vars
./pub/roles/python2/vars
./pub/roles/python3/vars
./pub/roles/R/vars
./pub/roles/sioyek-pdf/vars
./pub/roles/wallabag/varsAll of the returned paths indeed contain at least two files.
Note how we limited find to only directories named vars.
This is a one-liner that I find useful when deciding a free IPv4 address to assign a new container:
$ lxc network list-leases lxdbr0 | grep STATIC | sort -t "." -n -k4
| taipei | 00:16:3e:9c:dd:28 | 10.252.116.3 | STATIC |
| hunan | 00:16:3e:f7:4f:b2 | 10.252.116.4 | STATIC |
| xian | 00:16:3e:b0:54:12 | 10.252.116.5 | STATIC |
| samarkand | 00:16:3e:e8:79:60 | 10.252.116.6 | STATIC |
| karachi | 00:16:3e:e5:4c:47 | 10.252.116.7 | STATIC |
| lahore | 00:16:3e:f1:73:ab | 10.252.116.8 | STATIC |
| muscat | 00:16:3e:9a:89:05 | 10.252.116.9 | STATIC |
| antioch | 00:16:3e:92:79:ca | 10.252.116.11 | STATIC |
| delhi | 00:16:3e:22:9c:d0 | 10.252.116.13 | STATIC |
| bahrain | 00:16:3e:4b:b6:ee | 10.252.116.14 | STATIC |
| lusail | 00:16:3e:fd:1f:49 | 10.252.116.15 | STATIC |
| pergamon | 00:16:3e:0e:9c:82 | 10.252.116.16 | STATIC |The one-liner is simplified by the fact that only the IP address field contains dots, so we can use them as delimiters for sort without first having to sort on the column delimiters.
WireHole is a combination of WireGuard, Pi-hole, and Unbound in a docker-compose project with the intent of enabling users to quickly and easily create a personally managed full or split-tunnel WireGuard VPN with ad blocking capabilities thanks to Pi-hole, and DNS caching, additional privacy options, and upstream providers via Unbound.
Interesting... Via Awesome Wireguard.
This is an extension of the very common find ... -exec grep ... {} \; construct I use almost daily to find which files contain a particular text string.
Now, let's say you're looking for files in all your Ansible roles containing the string ppa:, because you want to create a new role using a suitable existing role as a template. In this case, I think most recently modified is an excellent proxy for suitability.
Thus, the challenge: can we tack on something to the find ... grep construct such that the output shows matching files in order of most recently modified?
taha@asks2:~
$ cd /media/bay/taha/projects/ansible && find . -not -path '*/legacy/*' -type f -name "*.yml" -exec grep -il "ppa:" {} \; -printf "%T+ %p\n" | grep -v "^\\./.*" | sort && cd $OLDPWD
2021-06-09+22:27:20.6889730070 ./roles/public/php-versions/tasks/setup-Debian.yml
2022-01-09+07:39:51.1836426130 ./roles/public/java-openjdk/tasks/ppa.yml
2022-02-23+15:33:13.2318546100 ./roles/dev/deluge/tasks/install.yml
2022-03-31+04:42:16.5644336650 ./roles/dev/editor-notepadqq/tasks/main.yml
2022-05-09+15:21:01.7974094830 ./roles/dev/qownnotes/tasks/main.yml
2022-06-25+02:46:13.0580097480 ./playbooks/workstation/roles/boot-grub/tasks/main.yml
2022-06-25+02:46:18.2940273650 ./roles/dev/libreoffice/tasks/main.yml
2022-07-03+00:16:44.5563131800 ./roles/dev/shutter/tasks/main.yml
2022-07-04+20:35:15.6128270470 ./roles/dev/magnus/tasks/main.yml
2022-07-14+21:09:01.6502524570 ./roles/dev/flatpak-remote/tasks/main.yml
2022-07-14+22:05:43.3325667290 ./roles/public/firejail/tasks/install.yml
2022-07-16+13:42:04.3756138100 ./roles/public/variety/tasks/main.yml
2022-07-16+22:05:52.0552035060 ./roles/public/browser-chromium/tasks/install.yml
2022-07-21+00:14:51.1137716920 ./roles/public/foliate-ebookreader/tasks/ppa.yml
2022-07-21+03:07:42.2876610030 ./roles/public/graphics-driver-nvidia/tasks/install.yml
2022-07-21+06:05:27.4514643180 ./roles/public/foliate-ebookreader/tasks/flatpak.yml
2022-07-23+18:32:46.8466638700 ./roles/dev/handbrake/tasks/main.yml
2022-08-12+00:09:51.6575729520 ./roles/dev/x2goclient/tasks/main.yml
2022-08-19+15:28:49.5605481840 ./roles/dev/x2goserver/tasks/main.yml
2022-11-04+11:35:14.6208169990 ./roles/public/python3/tasks/python-ppa.yml
2022-11-19+03:16:16.7832183030 ./roles/public/browser-firefox/tasks/main.yml
2022-12-24+23:04:01.2033026010 ./roles/public/R/tasks/dependencies.yml
2022-12-31+19:38:32.9105553030 ./roles/public/digikam/tasks/install-ppa.yml
2023-01-01+01:39:08.2045090970 ./roles/public/digikam/tasks/install-appimage.yml
2023-01-14+00:44:34.8526187360 ./roles/public/java-openjdk/defaults/main.yml
2023-01-26+14:10:18.9247087870 ./roles/public/ansible/tasks/main.yml
2023-01-26+16:14:59.9903243110 ./roles/public/sioyek-pdf/defaults/main.yml
2023-05-12+12:01:30.4705549280 ./roles/public/mpv/tasks/install.yml
2023-05-13+00:47:41.1561557100 ./roles/public/nextcloud-desktop/tasks/main.yml
2023-08-27+18:19:44.8291334420 ./roles/public/digikam/defaults/main.ymlEureka!
Explainer
- the initial
cd <path-parent>ensure that the resulting paths displayed byfinddon't contain the<path-parent>part (to avoid cluttering the output), and the finalcd $OLDPWDjust make sure that the bash prompt is not changed to<path-parent>. - unless you want to exclude some path from the search, there is obviously no need for
-not -path '*/<some-path>/*'. grep -ifor case insensitive matching, and-l(that's the letterlfor list) makesgrepprint only the filename and not each matching line (this is crucial for this hack to work, we wantgrepto produce as little output as possible, in fact, if I could figure out a way to silencegrepaltogether I would have, but I couldn't).-printf "%T+ %p\n"adds the filemtimeto the output (on a new line). Thanks angus@Unix.SE.
At this point, an example of the unfinished product is order. Before sorting, and before the final grep -v, the output looks like this (excerpt):
taha@asks2:~
$ cd /media/bay/taha/projects/ansible && find . -not -path '*/legacy/*' -type f -name "*.yml" -exec grep -il "ppa:" {} \; -printf "%T+ %p\n" && cd $OLDPWD
./roles/public/java-openjdk/defaults/main.yml
2023-01-14+00:44:34.8526187360 ./roles/public/java-openjdk/defaults/main.yml
./roles/public/java-openjdk/tasks/ppa.yml
2022-01-09+07:39:51.1836426130 ./roles/public/java-openjdk/tasks/ppa.yml
./roles/public/browser-firefox/tasks/main.yml
2022-11-19+03:16:16.7832183030 ./roles/public/browser-firefox/tasks/main.yml
./roles/public/R/tasks/dependencies.yml
2022-12-24+23:04:01.2033026010 ./roles/public/R/tasks/dependencies.yml
./roles/public/browser-chromium/tasks/install.yml
2022-07-16+22:05:52.0552035060 ./roles/public/browser-chromium/tasks/install.yml
./roles/dev/x2goclient/tasks/main.yml
2022-08-12+00:09:51.6575729520 ./roles/dev/x2goclient/tasks/main.ymlwith the grep output on its own line, followed by the time-stamped output of printf. Like I said, it would have been better if we could somehow silence the grep output at this point. If you know a way, feel free to let me know!
As expected, sorting resulted in the non-time-stamped lines dangling about like some unwanted appendage:
taha@asks2:~
$ cd /media/bay/taha/projects/ansible && find . -not -path '*/legacy/*' -type f -name "*.yml" -exec grep -il "ppa:" {} \; -printf "%T+ %p\n" && cd $OLDPWD
2022-01-09+07:39:51.1836426130 ./roles/public/java-openjdk/tasks/ppa.yml
2022-07-16+22:05:52.0552035060 ./roles/public/browser-chromium/tasks/install.yml
2022-08-12+00:09:51.6575729520 ./roles/dev/x2goclient/tasks/main.yml
2022-11-19+03:16:16.7832183030 ./roles/public/browser-firefox/tasks/main.yml
2022-12-24+23:04:01.2033026010 ./roles/public/R/tasks/dependencies.yml
2023-01-14+00:44:34.8526187360 ./roles/public/java-openjdk/defaults/main.yml
./roles/public/java-openjdk/tasks/ppa.yml
./roles/public/browser-chromium/tasks/install.yml
./roles/dev/x2goclient/tasks/main.yml
./roles/public/browser-firefox/tasks/main.yml
./roles/public/R/tasks/dependencies.yml
./roles/public/java-openjdk/defaults/main.ymlAt this point I was out of ideas, so grep -v ... it was, and we end up with the one-liner shown above. It's an ugly hack, but hey, it works :-)
Bash 5.1 on Ubuntu 22.04.3, with GNU find 4.8.0, GNU grep 3.7, and GNU sort 8.32.
This is just a quick-and-dirty one-liner. I was compiling beamer slides, and for some reason the TikZ-generated PDF figures contained two pages under some circumstances. This way we can quickly see whether just some PDF files or all of them suffered a problem:
$ find figure/ -type f -name "*.pdf" -exec pdftk "{}" dump_data \; | grep NumberOfPages | awk '{print $2}'
1
1
1
1
1
1(in this case they were all one page long).
Passwordstore is a great password manager, and I rely on it also in my Ansible playbooks, where it works by causing the gpg-agent to prompt me for the passphrase of my gpg key.
This prompt is a GUI prompt, which is very suitable when sitting at the computer in question. But a small annoyance is that it does not work at all when working on a remote computer via ssh (the prompt shows up on the remote computer's desktop, and the Ansible playbook in the terminal just freezes until it eventually fails).
It would be so much nicer if those ssh terminal sessions would instead get the gpg-agent prompt in the terminal. So far I have not found a method that achieves this without also sacrificing the GUI desktop prompt for non-remote work.
Desktop and laptop running Ubuntu 22.04 with i3wm desktop.
The relevant parts of my config can be seen in https://codeberg.org/ansible/dotfiles.
I considered the following related Q:s&A:s but did not achieve the desired outcome.
- https://unix.stackexchange.com/questions/554153/what-is-the-proper-configuration-for-gpg-ssh-and-gpg-agent-to-use-gpg-auth-sub
- https://stackoverflow.com/questions/17769831/how-to-make-gpg-prompt-for-passphrase-on-cli
- https://superuser.com/questions/1189602/how-to-configure-gpg2-to-ask-for-passphrase-on-the-console-instead-of-in-a-popup
- https://unix.stackexchange.com/questions/217737/pinentry-fails-with-gpg-agent-and-ssh
Some more tests
In the SSH session (no effect, unfortunately):
gpg-connect-agent updatestartuptty /byeLearned that the gpg-agent is running in --supervised mode, and its ENV variables include DISPLAY=:0:
solarchemist@desktop:~
$ sudo cat /proc/2652288/environ
HOME=/home/solarchemist LANG=en_US.UTF-8 LC_TIME=sv_SE.UTF-8 LOGNAME=solarchemist
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/bin
SHELL=/bin/bash SYSTEMD_EXEC_PID=2652288 USER=solarchemist
XDG_DATA_DIRS=/home/solarchemist/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share/:/usr/share/:/var/lib/snapd/desktop
XDG_RUNTIME_DIR=/run/user/1000 QT_ACCESSIBILITY=1
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus DISPLAY=:0 XAUTHORITY=/home/solarchemist/.Xauthority
MANAGERPID=1532 LISTEN_PID=2652288 LISTEN_FDS=4
LISTEN_FDNAMES=browser:extra:std:ssh INVOCATION_ID=<stuff> JOURNAL_STREAM=<stuff>(the PID of the gpg-agent process is easily identified with ps aux | grep [g]pg).
Manual work-around
Manual work-around is to set pinentry-program /usr/bin/pinentry-tty in ~/.gnupg/gpg-agent.conf and reload the agent gpg-connect-agent reloadagent /bye.
To revert to the default (GUI) pinentry behaviour, just remove the line and reload the agent again.
How could we go about to draw a straight line (vertical or horizontal) on top of any other window on our Linux desktop? I'm using i3 window manager with picom compositor at present, so I'm primarily interested in solutions that works for that.
I should get back to this question in the future and implement a nicer solution than pango-view
pango-view
Produces a vertical line (actually, more of a vertical box of limited width).
Very easy to make it, just issue the command in a terminal. pango-view was already installed.
$ pango-view --height=99999 --margin=1 --background=red -t ''- https://forum.puppylinux.com/viewtopic.php?p=76743 relevant, very good and recent
- https://askubuntu.com/questions/328543/are-there-any-tools-for-drawing-on-the-desktop-drawing-over-apps
gromit-mpxis a good over-app painter, but does not provide perfectly straight lines- https://www.linuxfordevices.com/tutorials/linux/tools-to-draw-on-linux-screen
Will add more as I learn about them. I only care about FOSS projects.
LXD
See my Ansible role that installs and configures LXD and provisions LXC containers.
Docker
I have some experience with Docker containers. Prefer LXC if I have the choice.
I have written an Ansible playbook to setup containers with docker-compose as part of a as-yet not-public project for InvenioRDM.
Podman
No hands-on experience yet.
Singularity
Hm, interesting. Could it be better than Docker for sharing something like a thesis with "all batteries included", I wonder?
Singularity can convert Docker containers to Singularity, or can run containers directly from Docker Hub
https://blogs.oregonstate.edu/learningbydoing/2022/01/04/docker-and-singularity-containers-which-one-is-better/
Learn the skills required to sysadmin a remote Linux server from the commandline.
Course restarts every first Monday of the month
I wanted to create an ASCII art "bismillah" for use in the terminal.
Found this beautiful calligraphy by Nuria Garcia Masip. After cropping it, rotating it slightly and making the background monochromatic, I tried the ascii-image-converter by Zoraiz Hassan, and it worked great with the --braille flag:
This converter tool was really easy to install (just run the binary), and the output was automatically resized to fit the terminal window size, which was a convenient feature.
I discovered some other ASCII art CLI tools (never tested them though):
Recently installed a new webcam by my office computer. Not long after, a thought materialised: should it not be possible to view the video feed over a remote SSH tunnel?
Indeed, here's one way to do it (I have not bothered connecting to the camera's builtin microphone, but that should be possible):
taha@asks2:~
$ ssh mkem150 "ffmpeg -i /dev/video0 -c:v libx264 -f mpegts -" | mpv -
[file] Reading from stdin...
ffmpeg version 4.4.2-0ubuntu1~18.04.sav1.4 Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
configuration: --prefix=/usr --extra-version='0ubuntu1~18.04.sav1.4' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librist --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-crystalhd --enable-libmfx --enable-libsvtav1 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 70.100 / 56. 70.100
libavcodec 58.134.100 / 58.134.100
libavformat 58. 76.100 / 58. 76.100
libavdevice 58. 13.100 / 58. 13.100
libavfilter 7.110.100 / 7.110.100
libswscale 5. 9.100 / 5. 9.100
libswresample 3. 9.100 / 3. 9.100
libpostproc 55. 9.100 / 55. 9.100
Input #0, video4linux2,v4l2, from '/dev/video0':
Duration: N/A, start: 47325.806919, bitrate: 442368 kb/s
Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1280x720, 442368 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x564e46b7b780] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x564e46b7b780] profile High 4:2:2, level 3.1, 4:2:2, 8-bit
Output #0, mpegts, to 'pipe:':
Metadata:
encoder : Lavf58.76.100
Stream #0:0: Video: h264, yuv422p(tv, progressive), 1280x720, q=2-31, 30 fps, 90k tbn
Metadata:
encoder : Lavc58.134.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
(+) Video --vid=1 (h264 1280x720 30.000fps)ime=00:00:00.90 bitrate=1983.6kbits/s speed=0.198x
VO: [gpu] 1280x720 yuv422pWorked without -c:v libx264, but noticeably poor video quality (pixelation and such).
Does not work if we remove the -f mpegts argument.
This is a neat way to quickly generate a QR-code, for example to transfer text from computer to phone (thanks to Solène Rapenne for the original idea and implementation). On the phone, you'll of course need to use a QR-reader app, such as Binary Eye.
xclip -o -selection clipboard | qrencode -o - -t PNG | feh -g 600x600 -Z -Using this command, whatever is in your clipboard will be encoded to QR and displayed on your monitor. Note that xclip can pull stuff from different clipboards, and in my case the contents were not picked up with -selection default but -selection clipboard did the trick.
Linux (well, really the window managers, so X11 and then, i3, Wayland, etc…) have multiple clipboards. The default ones are the Primary selection one, and the Secondary one. The names are historical accidents, but the “primary” one always has a copy of the last text you selected from anywhere, which can be pasted anywhere by clicking the middle mouse button. You just select some text and that’s it - you don’t have to do anything else and you can then middle-click paste this anywhere. The “secondary” clipboard is the “normal” Cut, Copy, Paste, Ctrl+c, Ctrl+v one.
https://duncanlock.net/blog/2022/04/06/using-windows-after-15-years-on-linux/
- i3wm, tiling window manager for X11.
- sway, drop-in replacement for i3wm on Wayland.
- enlightenment, window manager, compositor and minimal desktop. Not tiling. Supports X11, experimental Wayland support.
There are many more window managers. Add more as I (re)discover them.
Guides and how-tos
- Introduction to Ansible playbooks
- Playbooks vs roles, and explain the difference between task, role, play and playbook
- How to install and configure Ansible on Ubuntu 18.04 - DigitalOcean
- Linux hardening using idempotency with Ansible
Ansible playbooks and roles
- I haven't published all roles that I've written, but all the roles that I do publish are collected at codeberg.org/ansible
- Ansible module (Python code) to install R packages, by yutannihilation
- Ansible role to install TeXLive
- https://ansible.jeffgeerling.com/
- https://robertdebock.nl/ansible.html