Tag: Grub2

Make Grub2 Boot Older Kernel Version in Ubuntu 20.04

Posted on by David Yang

In a Linux system, we may have multiple kernels installed. Usually, it is the latest kernel configured to be the default one the system boot loader will use during automatic boot if there is no manual kernel choosing. In many cases, such as there is no driver ready yet for some devices in newer kernels,
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How to detect whether Linux runs in UEFI or BIOS mode inside the Linux?

Posted on by Eric Ma

How to detect whether Linux runs in UEFI or BIOS mode inside the Linux itself without needed to boot the the management console of the mother board? You can detect whether Linux runs in EFI mode by checking whether /sys/firmware/efi exist. In bash, you can test by [ -d /sys/firmware/efi/ ] This technique is used
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How to Add “nomodeset” to Grub2 in Fedora and Ubuntu

Posted on by Eric Ma

I need to add nomodeset to make my GPU card work on Linux. Latest Fedora and Ubuntu and their derives use grub2. How to add nomodeset permanently to grub2 on Fedora and Ubuntu? The parameters grub2 will use are stored in its grub.cfg file. The grub.cfg file is generated from grub’s default settings file /etc/default/grub.
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How to make Linux automatically reboot after a kernel panic?

Posted on by Eric Ma

After a kernel panic, it is impossible to remotely connect to the Linux server to reboot it by SSH. How to make the panic kernel automatically reboot itself? Linux kernel has a nice feature that reboots itself after a timeout when a kernel panic happened. Usually, it is disabled by default. To turn it on,
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How to boot Linux Mint to the console by default?

Posted on by Eric Ma

How to boot Linux Mint to the console by default? (that is, the run level 3). 2 methods introduced here to boot Linux Mint to console/command line. Method 1 (may only work for earlier releases; check method 2 below): set kernel option. Edit /etc/default/grub and add text to GRUB_CMDLINE_LINUX_DEFAULT: GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash text” Then, re-generate grub
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How to upgrade Fedora 19 to Fedora 20 through the network?

Posted on by Eric Ma

How to upgrade Fedora 19 to Fedora 20 through the network? The tool for Fedora to upgrade the distribution is FedUp. Check this page for how to upgrade Fedora 19 to Fedora 20: http://fedoraproject.org/wiki/FedUp#How_Can_I_Upgrade_My_System_with_FedUp.3F Be sure to check the bugs in Fedora 20 before the upgrading: http://fedoraproject.org/wiki/Common_F20_bugs#Upgrade_issues Generally, it contains 3 steps: Preparation # yum
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Building and Installing Linux Kernel from the Source Code in an Existing Linux OS

Posted on by Eric Ma

Building Linux kernel may sound a complex and geek-only thing. However, as Linux kernel itself has much less depended tools/packages compared to other software packages, it is quite easy to compile, build and install a Linux kernel from the source code in an existing Linux OS. Building Linux kernel is needed if you need to
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How to Regenerate Grub2 Config Files on Linux

Posted on by Eric Ma

Grub2 config file may need to be re-generated after changing Grub2 configurations such as configuration changes and setting default boot entries. The Grub2’s config file may be at different locations depending on your Linux distro and whether your Linux is booted in BIOS or UEFI mode. This makes regenerating Grub2 config file not easy for
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Lazy Linux Admins Going to Server Rooms Less: Forced Reboot, Auto Reboot after Kernel Panic and Email Notification after Reboot

Posted on by Eric Ma

Having to go the the server room to reset servers is the most headache thing for admins managing a cluster of Linux servers in a remote site. Either you can ping the server but can not ssh to it, or you even can not ping it. There are various reasons that may cause a Linux
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How to Configure Linux Kernel Video Mode for 32-bit and 16-bit Boot Protocols

Posted on by Eric Ma

The Linux kernel has a generic driver for a graphic framebuffer named vesafb on intel boxes. It provides a nice large console for most of modern displays. Setting VESA modes for Linux kernel with 32-bit and 16-bit boot protocol are different. We introduce both methods here. Linux kernel with 32-bit boot protocol For machine with
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Installing Xen on Fedora 20 as Domain-0

Posted on by Eric Ma

I ever introduced [[installing-xen-domain-0-on-fedora-17]] as the first try to use the xen package delivered from Fedora and get away from manually compiling Xen and patching the kernel. In this post, I introduce installing Xen Dom0 on Fedora 20. Installing Xen First, install the xen pacakges: # yum install xen The Linux kernel is already ready
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How to Install Xen on Fedora as Domain-0 (Fedora 17)

Posted on by Eric Ma

The new development of Xen and Linux kernel make it easy to install Xen on Fedora as the Domain-0 now. This post uses Fedora 17 as an example platform to introduce how to set up Domain-0 on Fedora Linux. Compared to our old method (https://www.systutorials.com/setting-up-stable-xen-dom0-with-fedora-xen-3-4-3-with-xenified-linux-kernel-2-6-32-13-in-fedora-12/) which requires manually compiled Xen and patched kernel, the current
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How to Set Default Entry in Grub2 and Grub

Posted on by Eric Ma

Linux booting is usually controlled by Grub or the new Grub2. Setting the default booting entry is a frequent operations. Here, we introduce how to set the default entry in Grub2 and Grub. Setting the default booting entry in grub2 Note1: With some version of grub2, the grub2-set-default method and the script below may not
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How to Upgrade Fedora to Newer Version with Yum

Posted on by Eric Ma

The latest tools for upgrading Fedora is FedUp, please check How to upgrade Fedora 19 to Fedora 20 through the network. Please consider PreUpgrade for upgrading Fedora. This is the recommended method. This post makes a list of actions should be done to upgrade Fedora using yum. Please note that this is for experienced users
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