lukas.zapletalovi.comBlog - Lukáš Zapletal

Lukáš Zapletal: engineer in pyjama Students Archive About me Contact Foreman development setup with libvirt 2020 Thanks to dnsmasq DHCP Foreman plugin, development setup for provisioning can be little bit easier. After git checkout of Foreman core, Smart Proxy and Smart Proxy DHCP Dnsmasq plugin, perform creation of initial directory structure: # DEVELOPER=lzap # mkdir /var/lib/libvirt/dnsmasq/foreman-default # chown $DEVELOPER:dnsmasq /var/lib/libvirt/dnsmasq/foreman-default # touch /var/lib/dnsmasq/foreman-default.leases # chown $DEVELOPER:dnsmasq /var/lib/dnsmasq/foreman-default.leases # mkdir /var/lib/dnsmasq/tftp # chown $DEVELOPER:dnsmasq /var/lib/dnsmasq/tftp/ # setfacl -m u:$DEVELOPER:r-- /var/lib/libvirt/dnsmasq/default.conf Copy PXELinux files, this will work also for Grub2 or iPXE: # cp /usr/share/syslinux/*.{bin,c32,0} /var/lib/dnsmasq/tftp Finally, change libvirt “default” network configuration in the following way. The difference between the default configuration are the following elements or attributes: tftp bootp dnsmasq:options xmlns:dnsmasq default 25fd4c6e-4d9e-45a6-b448-57900c3315f2 Restart libvirt network named “default” and you are good to go. Note in this setup I haven’t configured DNS, therefore unattended_url must be set to something like http://192.168.122.1:3000 . Read on 22 September 2020 | linux | fedora Creating Windows 10 bootable USB drive I had to update firmware for my super-ultra-wide LG monitor, however the utility only works in Windows and requires USB-C PC or laptop. I have one, but it’s Fedora only. Luckily, there is a way how to install Windows 10 to USB hdd (or flash). First of, download Windows 10 ISO from Microsoft’s website. I’ve used MediaCreationTool.exe utility which prepared the ISO for me in about half an hour. Next up it’s this wonderful freeware tool called Rufus . By default it only shows USB flash drives, but after pressing Ctrl-Alt-F it also shows up USB external HDD drives. Pick a drive, browse the ISO and after the tool asks for type of installation select “Windows 10 To Go”. That’s all, really. Rufus will format the drive and copy necessary files. After the initial reboot Windows 10 sets them up and allows the trial period without activation. I was able to download a firmware update tool and perform what I needed to do. Everything was a little bit too slow on my USB 3.0 SATA HDD, but it was fine for the job. I hope that helps someone else using Linux! Read on 22 September 2020 | linux | fedora Overriding Gnome application command arguments Google Chrome 85, which I use as a secondary browser, introduced a regresion for AMD GPUs and I have to provide it a command line option in order to mitigate the problem. I was trying to find if there is any way to override or redefine just the Exec line of the desktop entry ( app.desktop file) but it looks like it can’t be done . The solution is to copy desktop entry specification from /usr/share/applications to home folder. Do not change the file name if you want to override the system-wide specification, do change the file name when you want to have a copy (another icon/app). In my case, I do only want a single Google Chrome entry: cp /usr/share/applications/google-chrome.desktop ~/.local/share/applications I’ve edited the file putting the required “use-cmd-decoder” GPU workaround. Note the new desktop action called “New Insecure Windows” which starts new session in insecure mode when server certificate errors are ignored. I only use this to access test machines signed with self-signed CA certificates, do not use this for real web! $ cat ~/.local/share/applications/google-chrome.desktop [Desktop Entry] Version=1.0 Name=Google Chrome GenericName=Web Browser GenericName[cs]=WWW prohlížeč Comment=Access the Internet Comment[cs]=Přístup k internetu # https://bugs.chromium.org/p/chromium/issues/detail?id=1122224 Exec=/usr/bin/google-chrome-stable %U --auth-server-whitelist="*redhat.com" --use-cmd-decoder=validating StartupNotify=true Terminal=false Icon=google-chrome Type=Application Categories=Network;WebBrowser; MimeType=application/pdf;application/rdf+xml;application/rss+xml;application/xhtml+xml;application/xhtml_xml;application/xml;image/gif;image/jpeg;image/png;image/webp;text/html;text/xml;x-scheme-handler/ftp;x-scheme-handler/http;x-scheme-handler/https; Actions=new-window;new-private-window;new-insecure-window; [Desktop Action new-window] Name=New Window Name[cs]=Nové okno Exec=/usr/bin/google-chrome-stable [Desktop Action new-private-window] Name=New Incognito Window Name[cs]=Nové anonymní okno Exec=/usr/bin/google-chrome-stable --incognito [Desktop Action new-insecure-window] Name=New Insecure Window Name[cs]=Nové nezabezečené okno Exec=/usr/bin/google-chrome-stable --incognito --allow-running-insecure-content --ignore-certificate-errors No need of restarting, Gnome automatically picks the changes which is cool. That’s all I have for today. Read on 03 September 2020 | linux | fedora Prevent virt-manager from asking password Everytime I start virt-manager, the tool I use on an every-day basis, it asks for the root password. Because I use LVM for my VMs, I need to use system libvirt. Well, it’s pretty easy to get rid of this. All I need to do is to add myself to the “libvirt” group. Tested on Fedora. Run this as the user who needs to be added. Do not run this in “root shell” otherwise you add “root” to the group which is not a terrible thing to do, except it will not work like you intented: sudo usermod -a -G libvirt $(whoami) Done! Enjoy. Read on 21 August 2020 | linux | fedora Dropping Feedburner update RSS ATOM URL Hey, I am dropping Google Feedburner, please update the URL of the feed if you are reading this in your RSS. The new URL is: https://lukas.zapletalovi.com/atom.xml The old URL will continue work, but after Google acquired Feedburner the service did not see much development and features are being rather removed. Migrate today if you want to keep reading those random Linux + FOSS + devops notes of mine. Read on 06 August 2020 | linux | fedora ASUS B350 PLUS EFI settings for Linux It’s been two years on my Ryzen 1700, 32GB RAM and Saphire 5600XT however after Fedora reinstallation after (another) SSD failure I started experiencing random hangs of the graphical subsystem (I could still ssh to my workstation). Some people recommended turning off IOMMU, so I took the opportunity to upgrade to latest EFI firmware and review all my settings. These are the best (and safest) ASUS B350-PLUS changed firmware settings optimized for Linux from my own experience. CPU\SVM = Enabled CPU\SMT = Disabled AMD CBS\C-State = Disabled AMD CBS\IOMMU = Disabled Boot\Fast boot = Disabled Boot\Boot logo = Disabled Boot\POST delay = 2 sec Boot\Wait for F1 = Disabled Boot\Setup mode = Advanced This solves several issues I had in the past. Virtualization is turned off by default, SVM enables it. Multi-threading is enabled and although this is not a thread on AMD CPUs I like to turn this off as it caused some issues in the past. C-State and IOMMU can be problematic for AMD GPUs and the rest is just optimizing boot process for my LG screen as it does poweroff sometimes when using Fastboot. I also have ryzen-stabilizator script during the boot to turn off few more CPU flags to prevent from random MCE freezing. This has probably been fixed and workarounded in Linux kernel, but I am lazy to test this and I want to live on the safe side: # cat /etc/rc.d/rc.local #!/bin/sh /usr/local/bin/ryzen-stabilizator --disable-c6 --disable-boosting --disable-aslr -enable-psicworkaround The author of this tool suggests to set Power Supply Idle Control to Typical Current Idle, however I was not able to find this setting in my firmware. I will update this blogpost on the fly if I encounter any other instability of my setup in the future. Overall, I am quite happy with AMD-only hardware. Sure, it’s not as stable as Intel, but I am glad there’s a competition again in the industry. Read on ...