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Arch Linux

Reinstall a package

pacman -S <pkg_name>

Downgrading packages

Pacman

cd /var/cache/pacman/pkg/
pacman -U <pkg_file_name>

Yay

cd ~/.cache/yay/<package_folder>
pacman -U <file_name>.pkg.tar.zst

Pacman history

/var/log/pacman.log

Repairing the Pacman database

  • Boot using the Arch installation media.
  • Mount the system's root filesystem, e.g. mount /dev/sdaX /mnt as root.
  • If the system uses default database and directory locations, you can now update the system's pacman database and upgrade it via pacman --root=/mnt --cachedir=/mnt/var/cache/pacman/pkg -Syyu as root.

See more here: https://wiki.archlinux.org/index.php/pacman.

Switch environment from live to installed system

arch-chroot /mnt

Bypass invalid or corrupted package (PGP signature) error

pacman -U /var/cache/pacman/pkg/antergos-keyring-*.pkg.tar.xz

This work, since pacman doesn’t check sigs on local packages by default.

Skip a package from being upgraded

vim /etc/pacman.conf
IgnorePkg=<pkg1> <pkg2>

Start a service on system boot:

sudo systemctl enable <service_name>

Copy to clipboard

cat ~/.ssh/id_rsa.pub | xclip -selection clipboard

View the entire file with highlighted matches

egrep --color 'pattern|$' <file>

Clean old journal logs

journalctl --vacuum-size=500M

Show journal errors since the last boot

journalctl -p 3 -xb -1

Cut the video file

ffmpeg -i video.mp4 -ss 00:00:00 -t 00:00:20 -async 1 out.mp4

Scale the video file

ffmpeg -i input.mp4 -vf scale=400:-2 output400.mp4

Concatenate video files

printf "file '%s'\n" ./*.mp4 > mylist.txt
ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4

Compress the video file

ffmpeg -i input.mp4 -vcodec libx265 -crf 28 output.mp4

Note: a reasonable CRF range for H.265 may be 24 to 30 - lower CRF values correspond to higher bitrates, and hence produce higher quality videos.
Source: https://unix.stackexchange.com/a/38380

Clean old pacman packages

paccache -ruk0 # remove all uninstalled packages
paccache -dk 2 # dry-run
paccache -rk 2 # remove older than 2 last versions

Entering the recovery mode

  • in GRUB menu press e to edit the linux kernel's run entry
  • append rescue string at the end
  • press Ctrl + X to approve the changes

error while loading shared libraries: libicuuc.so: cannot open shared object file: No such file or directory

  • boot into a live system
  • mount /dev/sdaX /mnt
  • pacman -r /mnt -Syu

If needed

sudo mount -t proc /dev/sdaX /mnt/proc
sudo mount -t devtmpfs /dev/sdaX /mnt/dev
sudo mount -t sysfs /dev/sdaX /mnt/sys

Restore GRUB on an encrypted disk

NOTE: Make sure to boot the Live USB in the UEFI mode

In case of the following error: Waiting 30 seconds for device ‘/dev/disk/by-label/
cd dev/disk/by-label
ls
mv [Current name] [Missing name]

  • sudo su
  • cryptsetup open /dev/sdaX CryptName
  • mount /dev/mapper/CryptVolumeGroupName-rootvol /mnt
  • mount /dev/sda2 /mnt/boot
  • mount /dev/sda1 /mnt/boot/efi
  • arch-chroot /mnt
  • grub-mkconfig -o /boot/grub/grub.cfg
  • grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=Antergos-grub

UPDATED:

With Rufus v3 make bootable USB in UEFI (MBR) mode. F12 to show the boot menu.

  • sudo su
  • # (optional) check partitions IDs
    fdisk -l
  • cryptsetup open /dev/nvme0n1p7 mycrypt
  • mount /dev/mapper/mycrypt /mnt
  • # list volumes
    btrfs subvolume list -p /mnt
  • umount /mnt
  • mount -o subvol=@ /dev/mapper/mycrypt /mnt
  • mount -o subvol=@log /dev/mapper/mycrypt /mnt/var/log
  • mount -o subvol=@cache /dev/mapper/mycrypt /mnt/var/cache
  • mount -o subvol=@home /dev/mapper/mycrypt /mnt/home
  • mount /dev/nvme0n1p6 /mnt/boot/
  • mount /dev/nvme0n1p1 /mnt/boot/efi
  • arch-chroot /mnt/
  • grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=EndeavourOS-grub
  • grub-mkconfig -o /boot/grub/grub.cfg

➡ https://discovery.endeavouros.com/system-rescue/repair-a-non-booting-grub/2021/03/

Encrypt external drive

  1. In GParted, change the partition table from MSDOS to GPT
  2. Create an unformatted partition on the disk
  3. Check partition ID with lsblk --fs, e.g. sda1
  4. sudo cryptsetup --sector-size=512 luksFormat /dev/sda1
  5. sudo cryptsetup open /dev/sda1 drive -> run lsblk -> "drive" should appear on the list
  6. sudo mkfs.btrfs /dev/mapper/drive
  7. sudo mount /dev/mapper/drive /mnt/
  8. Verify it mounted without issues
  9. sudo umount /mnt
  10. sudo cryptsetup close drive
  11. Open the drive in file manager UI and decrypt it
  12. Run lsblk --fs to get the partition UUID
  13. sudo chown marek:marek /run/media/marek/c0bfaf54-8574-4ac1-ab9a-db166deb96e9

➡ https://www.youtube.com/watch?v=ZNaT03-xamE

Reinstall all packages

chroot steps from above and then:

pacman -Qqn | pacman -S -

force reinstall a specific package:

pacman -S --overwrite "*" linux

Changing default app

Check the current default for mime type:

xdg-mime query default inode/directory

Update the default:

xdg-mime default org.gnome.Nautilus.desktop inode/directory

➡ https://www.youtube.com/watch?v=z3F0hTigMvU

List packages that depend on a package

pacman -Qi ruby-xdg | grep 'Required'

Strip metadata from image files

mogrify -auto-orient -strip ./*.jpg

Compress and resize images to reduce size

mogrify -resize 70% -quality 75 *.jpg

Compress PDF to reduce size

The industry standard for this is Ghostscript

\gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

Convert images into a PDF file

convert *.jpg -quality 75 Scanned.pdf

Convert PDF to image

pdftoppm -jpeg -r 300 input.pdf output

Merge two images into one

magick "image1.jpg" "image2.jpg" -auto-orient +append output.jpg

Show image GPS metadata

exiv2 -g "Exif.GPSInfo"  photo.jpg

Reset image GPS metadata

exiv2 -M "set Exif.GPSInfo.GPSLongitude 0/1 0/1 0/1" photo.jpg  
exiv2 -M "set Exif.GPSInfo.GPSLatitude 0/1 0/1 0/1" photo.jpg