omarchy-iso/configs/airootfs/usr/local/bin/omarchy-install-diagnose-media

#!/bin/bash
#
# Say whether an install failure was the install medium, and say it in words
# that name the fix.
#
# The ISO's offline mirror is bind-mounted onto the target's package cache for
# the duration of pacstrap (see _mount_offline_package_cache), so a package
# pacman calls corrupt under that path is a byte that came off the medium --
# nothing else ever writes there. That much is certain, and it is the part
# worth saying out loud, because the failure screen otherwise ends at "get help
# at discord" with the word USB nowhere on it.
#
# What is not certain is which way the medium failed. Bytes written wrong and
# bytes read wrong produce the same checksum mismatch, and pacstrap runs with
# --noconfirm, which answers yes to pacman's "delete it?" and unlinks the
# package through the bind mount before anything here can weigh it. So the
# usual verdict names the medium and gives both remedies in the order worth
# trying. When the package does survive, its checksum in the mirror's database
# tells the two apart, and then this says which.
#
# Prints the diagnosis on stdout, one line per line, headline first. Exits 1
# with no output when there is nothing here to diagnose, so the caller can ask
# unconditionally.

set -uo pipefail

TARGET_PACKAGE_CACHE="${OMARCHY_TARGET_PACKAGE_CACHE:-/mnt/var/cache/pacman/pkg}"
OFFLINE_MIRROR="${OMARCHY_OFFLINE_MIRROR:-/var/cache/omarchy/mirror/offline}"

if (( $# == 0 )); then
  echo "Usage: omarchy-install-diagnose-media <log-file>..." >&2
  exit 2
fi

# Only packages under the target cache count. A corrupt package anywhere else
# was not read off this ISO, and guessing wrong here sends someone to buy a USB
# stick they did not need.
corrupt_package() {
  local log match package=""

  for log in "$@"; do
    [[ -f $log ]] || continue
    match=$(sed -n "s|.*${TARGET_PACKAGE_CACHE}/\([^ ]*\) is corrupted.*|\1|p" "$log" | tail -n 1)
    [[ -n $match ]] && package="$match"
  done

  printf '%s' "$package"
}

expected_checksum() {
  local package="$1" reader

  [[ -f $OFFLINE_MIRROR/offline.db ]] || return 1

  if command -v bsdtar >/dev/null 2>&1; then
    reader=(bsdtar -xOf "$OFFLINE_MIRROR/offline.db")
  else
    reader=(tar -xOzf "$OFFLINE_MIRROR/offline.db")
  fi

  # repo-add writes %FILENAME% before %SHA256SUM% in every desc record, so the
  # name in hand when a checksum arrives is the name it belongs to. The wanted
  # name comes through the environment rather than -v, which would read a
  # backslash in a package version as an escape sequence.
  "${reader[@]}" 2>/dev/null | want="$package" awk '
    BEGIN { want = ENVIRON["want"] }
    $0 == "%FILENAME%" { getline name; next }
    $0 == "%SHA256SUM%" { getline sha; if (name == want) { print sha; exit } }
  '
}

actual_checksum() {
  local package="$1" sum

  [[ -f $OFFLINE_MIRROR/$package ]] || return 1
  sum=$(sha256sum "$OFFLINE_MIRROR/$package" 2>/dev/null) || return 1
  printf '%s' "${sum%% *}"
}

package=$(corrupt_package "$@")
if [[ -z $package ]]; then
  exit 1
fi

# The name reaches a terminal, and a package version may legally hold a
# backslash that the renderer would read as an escape. Strip anything a package
# filename has no business containing before printing it.
display_package="${package//[^A-Za-z0-9._+:@%-]/}"

expected=$(expected_checksum "$package")
actual=$(actual_checksum "$package")

# The package name goes on a line of its own throughout. Names run past fifty
# characters and the screen is only as wide as the logo, so a name sharing a
# line with the sentence that explains it truncates the explanation away. The
# blank line after it separates what happened from what to do about it.
if [[ -n $expected && -n $actual ]]; then
  if [[ $expected == "$actual" ]]; then
    # Intact now, so the bytes were misread rather than written wrong, and
    # re-downloading fixes neither of the things that could have done it.
    echo "The install medium was misread"
    echo "This package is intact on this ISO, so the download and the write were fine:"
    echo "$display_package"
    echo
    echo "Try another USB port or another stick, and test this machine's memory"
  else
    echo "The install medium is damaged"
    echo "This package no longer matches the checksum it was built with:"
    echo "$display_package"
    echo
    echo "Re-download the ISO, verify it with sha256sum, and write the USB again"
    echo "If a verified ISO fails here too, the USB stick itself is the problem"
  fi
  exit 0
fi

# The usual case: pacman deleted the package it rejected, so the medium is the
# answer but the manner of its failure is not recoverable from here.
echo "The install medium is damaged or misread"
echo "pacman rejected this package, read straight off this ISO:"
echo "$display_package"
echo
echo "Verify your download with sha256sum, then write the USB again"
echo "If the download verifies, the stick or this machine's memory is at fault"