Refactor kexec execution to handle sudo passwords

Major refactoring of the kexec execution logic to improve error
handling and fixing sudo password prompts which have been handled
incorrectly before because of setsid not allowing input terminal.

Also kexec errors are now displayed properly as bevore they were hidden.

Author: Qubasa

src/nixos-anywhere.sh

@@ -716,14 +716,63 @@ runKexec() {
     kexecUrl=${kexecUrl/"github.com"/"gh-v6.com"}
   fi
 
+  # Unified kexec error handling function
+  handleKexecResult() {
+    local exitCode=$1
+    local operation=$2
+
+    if [[ $exitCode -eq 0 ]]; then
+      echo "$operation completed successfully" >&2
+    else
+      # If operation failed, try to fetch the log file
+      local logContent=""
+      if logContent=$(
+        set +x
+        runSsh "cat /tmp/kexec-output.log 2>/dev/null" 2>/dev/null
+      ); then
+        echo "Remote output log:" >&2
+        echo "$logContent" >&2
+      fi
+      echo "$operation failed" >&2
+      exit 1
+    fi
+
+    # Clean up the log file
+    echo "Cleaning up remote kexec log file" >&2
+    (
+      set +x
+      runSsh "rm -f /tmp/kexec-output.log" 2>/dev/null || true
+    )
+  }
+
   # Define common remote commands template
   local remoteCommandTemplate
   remoteCommandTemplate="
+${enableDebug:+set -x}
+# Create a script that we can run with sudo
+kexec_script_tmp=\$(mktemp /tmp/kexec-script.XXXXXX.sh)
+trap 'rm -f \"\$kexec_script_tmp\"' EXIT
+cat > \"\$kexec_script_tmp\" << 'KEXEC_SCRIPT'
+#!/usr/bin/env bash
 set -eu ${enableDebug}
-${maybeSudo} rm -rf /root/kexec
-${maybeSudo} mkdir -p /root/kexec
-%TAR_COMMAND%
-TMPDIR=/root/kexec setsid --wait ${maybeSudo} /root/kexec/kexec/run --kexec-extra-flags $(printf '%q ' "$kexecExtraFlags")
+rm -rf /root/kexec
+mkdir -p /root/kexec
+cd /root/kexec
+echo 'Downloading kexec tarball (this may take a moment)...'
+# Execute tar command
+%TAR_COMMAND% && TMPDIR=/root/kexec setsid --wait /root/kexec/kexec/run --kexec-extra-flags $(printf '%q ' "$kexecExtraFlags")
+KEXEC_SCRIPT
+
+# Run the script and let output flow naturally  
+${maybeSudo} bash \"\$kexec_script_tmp\" 2>&1 | tee /tmp/kexec-output.log || true
+# The script will likely disconnect us, so we consider it successful if we see the kexec message
+if grep -q 'machine will boot into nixos' /tmp/kexec-output.log; then
+  echo 'Kexec initiated successfully'
+  exit 0
+else
+  echo 'Kexec may have failed - check output above'
+  exit 1
+fi
 "
 
   # Define upload commands
@@ -753,21 +802,46 @@ TMPDIR=/root/kexec setsid --wait ${maybeSudo} /root/kexec/kexec/run --kexec-extr
     localUploadCommand=(curl --fail -Ss -L "${kexecUrl}")
   fi
 
-  local tarCommand
-  local remoteCommands
+  # If no local upload command is defined, we use the remote command to download and execute
   if [[ ${#localUploadCommand[@]} -eq 0 ]]; then
     # Use remote command for download and execution
-    tarCommand="$(printf '%q ' "${remoteUploadCommand[@]}") | ${maybeSudo} tar -C /root/kexec -xv ${tarDecomp}"
+    local tarCommand="$(printf '%q ' "${remoteUploadCommand[@]}") | tar -xv ${tarDecomp}"
+    local remoteCommands=${remoteCommandTemplate//'%TAR_COMMAND%'/$tarCommand}
 
-    remoteCommands=${remoteCommandTemplate//'%TAR_COMMAND%'/$tarCommand}
+    # Run the SSH command - for kexec with sudo, we expect it might disconnect
+    local sshExitCode
+    (
+      set +x
+      runSsh sh -c "$(printf '%q' "$remoteCommands")"
+    )
+    sshExitCode=$?
 
-    runSsh sh -c "$(printf '%q' "$remoteCommands")"
+    handleKexecResult $sshExitCode "Kexec"
   else
+    # Query remote home directory for the user
+    remoteHomeDir=$(runSshNoTty -o ConnectTimeout=10 "getent passwd \"$sshUser\" | cut -d: -f6")
+    if [[ -z $remoteHomeDir ]]; then
+      abort "Could not determine home directory for user $sshUser"
+    fi
+
+    (
+      set +x
+      "${localUploadCommand[@]}" | runSsh "cat > \"$remoteHomeDir\"/kexec-tarball.tar.gz"
+    )
+
     # Use local command with pipe to remote
-    tarCommand="${maybeSudo} tar -C /root/kexec -xv ${tarDecomp}"
-    remoteCommands=${remoteCommandTemplate//'%TAR_COMMAND%'/$tarCommand}
+    local tarCommand="cat \"$remoteHomeDir\"/kexec-tarball.tar.gz | tar -xv ${tarDecomp}"
+    local remoteCommands=${remoteCommandTemplate//'%TAR_COMMAND%'/$tarCommand}
+
+    # Execute the local upload command and check for success
+    local uploadExitCode
+    (
+      set +x
+      runSsh sh -c "$(printf '%q' "$remoteCommands")"
+    )
+    uploadExitCode=$?
 
-    "${localUploadCommand[@]}" | runSsh sh -c "$(printf '%q' "$remoteCommands")"
+    handleKexecResult $uploadExitCode "Upload"
   fi
 
   # use the default SSH port to connect at this point