Beginner-Exploring-Linux

[![Author](https://img.shields.io/badge/Author-Senka_Wolf-4044ee?style=for-the-badge)](https://github.com/silentz) [![License](https://img.shields.io/badge/License-Apache--2.0-blue?style=for-the-badge)](./LICENSE.md) ![GitHub last commit](https://img.shields.io/github/last-commit/senkawolf/Software-List?style=for-the-badge)

Expand Table Here

- [CachyOS Install Process](#CachyOS-Install-Process) - [Troubleshooting](#Troubleshooting) - [Tweaks and Improvements](#Tweaks-and-Improvements) - [Guides](#Guides) - [Miscellaneous](#Miscellaneous)

CachyOS Install Process

Now we will be going through the install process of CachyOS, this will feel very familiar to a Windows setup.

Troubleshooting

VM Install - Asking for liveuser password

When booting from a USB media to instal CachyOS on a virtual machine you may be greeted by the below screen.

Live User Login Screen Screenshot

CachyOS doesn’t set passwords by default and there is no password. To get past the login screen switch your session to wayland then press enter with no password inputted and this will take you to the live desktop.

Snapper (Snapshot Setup) ^Wiki

Use this useful guide here.

System Freezes During Package Building - Out of Memory (OOM) ^Wiki

The Magic SysRq key is a powerful low-level feature in Linux that allows you to perform various commands directly to the kernel, even if the system seems completely unresponsive. It’s extremely useful for troubleshooting and safely recovering from system crashes.

This requires the SysRq functionality to be enabled in the kernel: Check by running

$ cat /proc/sys/kernel/sysrq

Below are the expected results: | Bit Value | Function | | — | — | | 0 | Disabled | | 1 | 0x1 → Fully Enable | | 2 | 0x2 → Enable sync (s) | | 4 | 0x4 → Enable remount read-only (u) | | 8 | 0x8 → Enable process signals (e and i) | | 16 | 0x10 → Enable reboot/poweroff (b and o) | | 32 | 0x20 → Enable unraw (r) | | 64 | 0x40 → Enable debug dumps (p, m) |

You want this to return 1 so all features are enabled. To change this run the following command.

$ sudo nano /etc/sysctl.d/99-sysrq.conf
$ #Then add the below line to the file and save
$ kernel.sysrq = 1
$ sudo sysctl --system #Apply the changes
$ cat /proc/sys/kernel/sysrq # Verify the changes, this should show 1 now.

Now you can fully use the Magic SysRq key feature, to do this you use the key combination:

Alt + SysRq (Print Screen) + <command key option>

Command Key	Action	Notes
`r`	Switch keyboard from raw to XLATE mode	Fixes frozen input
`e`	Send SIGTERM to all processes	Graceful shutdown attempt
`i`	Send SIGKILL to all processes	Forces processes to quit
`s`	Sync all filesystems	Flushes disk buffers
`u`	Remount all filesystems read-only	Prevents corruption
`b`	Reboot immediately	Hard reboot, does not sync disks
`o`	Power off immediately	Hard poweroff, does not sync disks
`t`	Dump task states	Useful for debugging frozen tasks
`m`	Show memory usage	Can help diagnose memory issues
`f`	Call OOM Killer on the current process	Useful if a single process is stuck

Safe Shutdown Sequence – REISUB

Mnemonic: “Raising Elephants Is So Utterly Boring”

Sequence for safely rebooting a frozen system:

Alt + SysRq + R  # Take control of keyboard
Alt + SysRq + E  # Send SIGTERM to processes
Alt + SysRq + I  # Send SIGKILL to processes
Alt + SysRq + S  # Sync filesystems
Alt + SysRq + U  # Remount filesystems read-only
Alt + SysRq + F  # Optional: kill current process if consuming all memory
Alt + SysRq + B  # Reboot

BTRFS Log Tree Startup Error

During startup if you get a simular error code to the below:

$ You are in emergency mode. After logging in, type "journalctl -xb" to view system logs, "systemctl reboot" to reboot, or "exit" to continue boot up.
$ Cannot open access to console, the root account is locked.
$ See sulogin(8) man page for more details
$ Press Enter to continue.
$ #Press enter then the following appears
$ Reloading system manager configuration.
$ Starting initr4.target
$ BTRFS: error (device nvme2n1p2 state A) in __btfrs_run_delayed_items:1181: errno=-17 Object already exists
$ BTRFS: error (device nvme2n1p2 state EAO) in do_abort_log_replay:190: errno=-17 Object already exists
$ BTRFS critical (device nvme2n1p2 state EAO): log tree (for root 257) leaf currently being processed (slot 44 key 23688878 12 74551):
$ BTRFS critical (device nvme2n1p2 state EAO): log replay failed in unlink_inode_for_log_replay:1062 for root 257, stage 3, with error -17: failed to run delayed items current inode 1720579 parents xt root 257
$ BTRFS: error (device nvme2n1p2 state EAO) in btrfs_recover_log_trees:7736: errno=-17 Object already exists
$ BTRFS: error (device nvme2n1p2 state EAO) in btrfs_replay_log:2094: errno=-17 Object already exists (failed to recover log tree)

The key points to the above message is

BTRFS critical: log replay failed
errno=-17 Object already exists
failed to recover log tree

This means:

The Btrfs journal (log tree) is corrupted.
Btrfs refuses to mount normally so boot halts.

To fix this we need to clear the Btrfs log:

Boot from a live USB (Use the same USB drive setup you used to install CachyOS). Next looking over the error it mentions device nvme2n1p2 which is the Btrfs partition witth the issue however we will confirm this in the steps below.

In the terminal:

$ lsblk -f #This lists block devices and shows filesystem-related information. In my case I should see "nvme2n1p2   btrfs"
$ sudo btrfs rescue zero-log /dev/nvme2n1p2 #Change nvme2n1p2 to match your device name!
$ reboot

What this does:

Deletes the corrupted journal
Does not delete your data
Forces a clean mount next boot

Once you are booted back into your system you should run the below command to verify checksums, repairs silent corruption using redundancy and gives peace of mind after a crash.

$ sudo btrfs scrub start -Bd /

[!NOTE] This happened to me during a yay install and build of a package.

Tweaks and Improvements

Enabling Parallel downloads

When using pacman to install and upgrade you can enable or allow more parallel downloads to speed up the process. To do so

$ sudo nano /etc/pacman.conf

Below is the first 42 lines from the config file. Look for ParallelDownloads = 5 and change this to 10.

#
# /etc/pacman.conf
#
# See the pacman.conf(5) manpage for option and repository directives

#
# GENERAL OPTIONS
#
[options]
# The following paths are commented out with their default values listed.
# If you wish to use different paths, uncomment and update the paths.
#RootDir     = /
#DBPath      = /var/lib/pacman/
#CacheDir    = /var/cache/pacman/pkg/
#LogFile     = /var/log/pacman.log
#GPGDir      = /etc/pacman.d/gnupg/
#HookDir     = /etc/pacman.d/hooks/
HoldPkg     = pacman glibc
#XferCommand = /usr/bin/curl -L -C - -f -o %o %u
#XferCommand = /usr/bin/wget --passive-ftp -c -O %o %u
#CleanMethod = KeepInstalled
#UseDelta    = 0.7
Architecture = auto

# Pacman won't upgrade packages listed in IgnorePkg and members of IgnoreGroup
#IgnorePkg   =
#IgnoreGroup =

#NoUpgrade   =
#NoExtract   =

# Misc options
#UseSyslog
Color
ILoveCandy
#NoProgressBar
#CheckSpace
VerbosePkgLists
DisableDownloadTimeout
ParallelDownloads = 5 #<<<<<<< Edit this line to be 10.
DownloadUser = alpm

Guides

[!CAUTION] All links here unless specified are NOT affiliated with me.

Miscellaneous

Sources

- [CachyOS](https://cachyos.org/)

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