Is it possible to shift+page-up to reveal the backtrace? The backtrace section ends with "---[ end trace 75435… ]---" If that's not possible, see if you can get a copy from /var/log after rebooting with a working kernel or when using a network disk. If that's not possible, and you have good reflexes, you could try ctr+s or scroll-lock to pause the kernel output at just the right moment, but it's probably easier to just set up remote logs:
Saturday, December 19. 2020
Debian Debugging During Install
Thursday, October 22. 2020
DP based BGP peering Router
Sunday, August 16. 2020
eBPF Tools
- BPF Portability and CO-RE - Compile Once - Run Everywhere
- eBPF - Security, Tracing & Profiling, Networking, Observability & Monitoring
From 2020/08/22 bpf@vger.kernel.org mailing list
What Yonghong suggested is to deprecate bpf_load.c completely, including a legacy way to attach kprobe, which will stay connected without proper clean up, if the application crashes. This has been a reason for multiple production problems so far and we've moved away from that, as a community.
There is no need to import anything from BCC, libbpf already supports this and much more. samples/bpf unfortunately are a bit outdated (and any help to bring them more in line with modern libbpf usage would be greatly appreciated!), the best place to look at better and more modern examples would be tools/testing/selftests/bpf in Linux repo, or for more realistic examples of building tracing tools, please check [0].
Tuesday, May 26. 2020
IQFeed on Linux throws ICMP Error
Seen on the IQFeed Developer Support 2020/04/21. A solution for allowing ICMP packets.
iqconnect.exe does a ping round trip against its DTN servers (you can see the ping results at IQConnect.log when you stop the feed and iqconnect.exe exits). Thing is, ping uses ICMP protocol, which in linux is somewhat privileged.
So, you need to give wine the appropiate permissions in order to be able to use ICMP. Running wine as root in order to circumvent this problem would be overkill (besides a very bad thing to do!), but fortunately you can use setcap in order to grant permissions in a much more granular way.
First, locate where your wine-preloader file is. In my case, it's on /usr/bin/wine-preloader . Then, type (yoo will need to sudo for this):
sudo setcap cap_net_raw+epi /usr/bin/wine-preloaderand that's all. Now wine is allowed to use ICMP protocol, which in turn will allow IQconnect.eze to make its "ping things" without complaining
Saturday, May 23. 2020
GUI From an LXC Container on the Host
I am almost embarrassed to say that I missed a good night's sleep sifting through erroneous out of date misinformation, missing some subtle distinctions, and winnowing out the chafe.
This all started when I wanted to give Krita a try for editing photographs. It is said it is the next best thing in open source when compared to PhotoShop. When installed on my Debian Linux workstation, all I could get out of it was crashes of one form or another. I'm not really surprised as my workstation has been through various combinations of buster, testing, bullseye, sid and experimental. Some package is out of sync somewhere.
So.. since I know how to run LXC containers, I figured I'd give that a try. That was successful, to a point. I used X2Go for remote console. But when my images are Nikon NEF files at 24Megapixels at 14bits each, file size, computation, and visualization are a bit of challenge (the screen updates being the main challenge). A wide erasure brush was slow, even on my speedy machine.
There are sites which vehemently say that there is no direct way to see the GUI from a container on a workstation host. Sigh. Misinformation. Then there are the five year old sites which show how it is done, but have extra commands, missing commands, or missing options. More sigh.
After much trial and error and trying the same things over again, with minor variations on the theme, in the hopes something might fix itself, it was a long night.
For the record, here is my research on a Debian Bullseye system with LXC '1:3.1.0+really3.0.4-3' Continue reading "GUI From an LXC Container on the Host" »
Wednesday, April 29. 2020
What can you preseed when installing Debian?
From Debian Misc Developer News (#51):
Steve McIntyre created[3] a debian-preseed[4] service that extracts all of the debconf templates in the Debian archive and lists each of the possible preseed options available along with their descriptions. If you want to repeat the extractions, you can use Steve's new Perl script or the existing tools on the preseed wiki page[5].
-- Paul Wise
Thursday, April 23. 2020
Reboot to BIOS in Linux
When one doesn't know the keystroke to get into the BIOS, one handy command to reboot from Linux:
# systemctl reboot --firmware-setup
Monday, March 16. 2020
Debian Preseed Updates in Bullseye Alpha 2 release
From the debian-boot mailing list:
* pkgsel: - Ensure tasksel is installed, regardless of its priority. - Add preseedable pkgsel/run_tasksel debconf template, making it possible (by setting it to false) to skip tasksel entirely (installation and prompt), while still benefiting from other pkgsel features. * preseed: - Update auto-install/defaultroot, replacing buster with bullseye.
Has loads of scripts and conditional actions going on, and is intended to work either from a remote server, or from a directory that d-i can see: hands.com/d-i/
he initrd of d-i can indeed be extended / appended. And in the "appendix" goes the desired extras. Then
d-i preseed/early_commands /myextras/early_script
Thursday, March 5. 2020
HostApd - Bug#927710: ath10k locks to regulatory domain US on ACPI platforms
The country code is not read from ACPI but from the EEPROM of the WiFi-card (0x0 "World Regulatory Domain" by default).
How to Build your Own Wireless Router (Part 3) - kernel requires code patch to enable 5GHz operations.
Wednesday, January 29. 2020
Linux Kernel 5.6
From Phoronix - Linux 5.6 To Bring FQ-PIE Packet Scheduler To Help Fight Bufferbloat, there are some example configurations for using different buffering mechanisms (Implementing the Flow Queue PIE AQM in the Linux Kernel).
For wireless clients:
net.core.default_qdisc=fq net.ipv4.tcp_congestion_control = bbrand fq_codel (codel) is better suited for router.
Another possibility:
I had pretty amazing results with cake. I prefer it over fq_codel and it is now part of main line since 4.19.
Cake - Common Applications Kept Enhanced
In the past the internet would just grind to a halt when the Apple devices started cloud syncing. They would totally swamp the outgoing bandwidth. Now nobody notices when an Apple device is syncing.
Open firmware for small routers for congestion management:
The OpenWrt issue with 4MB has to do with using newer kernels. For those devices, DD-WRT is a better bet (still on kernel 3.10).
Saturday, January 25. 2020
iPXE Boot
An extract from bug #949655 at bugs.debian.org:
I finally found on iPXE website[1] a link to detailed examples, including one[2] to boot pxelinux. It works perfectly with di-netboot-assistant:
#!ipxe dhcp set 210:string tftp://my_server/d-i/n-a/ chain ${210:string}pxelinux.0For those who did not know (like me ), 210 is a standard DHCP option called "path prefix"[3].
Monday, January 20. 2020
Linux Performance
- tuned is a profile-based system tuning tool that uses the udev device manager to monitor connected devices, and enables both static and dynamic tuning of system settings. Packages in Debian are 'tuned' and 'tuned-utils'.
- Using netstat and dropwatch to observe packet loss on Linux servers - uses the 'dropwatch' package (needs kernel symbols).
- Track a packet as it goes through the kernel (linux)
Linux Open Ports
Courtesy of 3 quick ways to reduce your attack surface on Linux, a command to identify open ports and identify the associated application:
$ ss -tulnp --no-header | awk '{print($1, $5, $7)}' udp 0.0.0.0:32770 users:(("vlc",pid=2786557,fd=39)) udp 0.0.0.0:32771 users:(("vlc",pid=2786557,fd=40)) udp 127.0.0.1:123 udp 0.0.0.0:123 udp 0.0.0.0:631 udp 0.0.0.0:37019 udp 0.0.0.0:5353 udp 0.0.0.0:39276 users:(("vlc",pid=2786557,fd=50)) udp 0.0.0.0:39277 users:(("vlc",pid=2786557,fd=51)) tcp 0.0.0.0:61209 tcp 127.0.0.1:25 tcp 127.0.0.1:5433 tcp 0.0.0.0:8794 tcp 127.0.0.1:3493 tcp 127.0.0.1:5101 users:(("ssh",pid=899751,fd=4)) tcp 127.0.0.1:5102 users:(("ssh",pid=2187130,fd=4)) tcp 127.0.0.1:5201 users:(("ssh",pid=2186389,fd=5)) tcp 127.0.0.1:5202 users:(("ssh",pid=2186389,fd=7)) tcp 0.0.0.0:22 tcp 127.0.0.1:631 tcp 127.0.0.1:5432 ...
Sunday, December 22. 2019
LXDE Screen Rotation Settings on Debian
On my Debian desktop, I have both of my primary monitors in portrait mode, with a third monitor in landscape mode. The login screen is therefore rotated 90 degrees from how it needs to be. After login, I need to manually go into System Settings, and manually rotate the monitors.
That is, up until now. A little poking around says I need to:
apt install arandr
This is a GUI application which will create a script in .screenlayout which can be auto-started upon login:
$ cat .screenlayout/bythree.sh #!/bin/sh xrandr \ --output DisplayPort-0 --primary --mode 3840x2160 --pos 0x8 --rotate right \ --output DisplayPort-1 --mode 3840x2160 --pos 2160x0 --rotate right \ --output DisplayPort-2 --off \ --output DisplayPort-3 --mode 2560x1600 --pos 4320x0 --rotate normal \ --output HDMI-A-0 --off \ --output HDMI-A-1 --off
This can be autostarted in LXDE with:
$ cat ~/.config/lxsession/LXDE/autostart @lxpanel --profile LXDE @pcmanfm --desktop --profile LXDE @xscreensaver -no-splash #@~/.screenlayout/bythree.sh <= does not work #@${HOME}/.screenlayout/bythree.sh <= does not work # make sure there is a line return at end of command: @/home/me/.screenlayout/bythree.sh
Instructions for the autostart file can be found at LXSession.