starting from scratch

backup.go

@@ -0,0 +1,120 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io/fs"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+func parseEnvironment(key string) string {
+	value := os.Getenv(key)
+	if value == "" {
+		log.Panicf("%s is not set\n", key)
+	}
+	if _, err := os.Stat(value); err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			log.Panicf("%s does not point to a valid path\n", key)
+		}
+		log.Panicf("trying to stat %s produced an unkown error\n", value)
+	}
+	return value
+}
+
+func parsePacmanConf() string {
+	var path string
+
+	file, err := os.Open("/etc/pacman.conf")
+	if err != nil {
+		log.Panicln(err)
+	}
+	defer func() {
+		if err := file.Close(); err != nil {
+			log.Panicln(err)
+		}
+	}()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.Contains(line, "DBPath") {
+			continue
+		}
+		path = strings.TrimSpace(strings.Split(line, "=")[1])
+		break
+	}
+
+	if _, err := os.Stat(path); err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			log.Panicln("DBPath in /etc/pacman.conf does not point to a valid path")
+		}
+		log.Panicf("trying to stat %s produced an unkown error\n", path)
+	}
+
+	return fmt.Sprintf("%s%s", path, "local")
+}
+
+func preBackup() {
+	pacmanDb := parsePacmanConf()
+	log.Printf("pacmanDb: %s\n", pacmanDb)
+	tmpPath := "/tmp/update/pre_backup"
+
+	output, err := exec.Command("pacman",  "--verbose", "--query").Output()
+	if err != nil {
+		log.Panicln(err)
+	}
+
+	err = os.MkdirAll(tmpPath, 0755)
+
+	err = os.WriteFile(fmt.Sprintf("%s/%s", tmpPath, "pre_pacman.txt"), output, 0644)
+	if err != nil {
+		log.Panicln(err)
+	}
+
+	defer func() {
+		if r := recover(); r != nil {
+			err := os.RemoveAll(tmpPath)
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			err = CopyDir(pacmanDb, fmt.Sprintf("%s/%s", tmpPath, pacmanDb))
+			if err != nil {
+				log.Panicln(err)
+			}
+
+			log.Println("recovered successfully")
+		}
+	}()
+
+	err = CopyDir(pacmanDb, fmt.Sprintf("%s/%s", tmpPath, pacmanDb))
+	if err != nil {
+		log.Panicln(err)
+	}
+}
+
+func postBackup() {
+	/*
+	 * basic logic for post:
+	 * create new pkg list and delete all lines which are the same as pre
+	 */
+	panic("unimplemented")
+}
+
+func main() {
+	// backup_dir := parseEnvironment("UPDATE_BACKUP_DIR")
+	cmdlineArg := os.Args[1]
+	log.Printf("cmdlineArg: %s\n", cmdlineArg)
+
+	if cmdlineArg == "pre" {
+		preBackup()
+	} else if cmdlineArg == "post" {
+		postBackup()
+	} else {
+		log.Panicf("invalid cmdline argument. supplied value was: %s\n", cmdlineArg)
+	}
+}

copy.go

@@ -0,0 +1,134 @@
+/* MIT License
+ *
+ * Copyright (c) 2017 Roland Singer [roland.singer@desertbit.com]
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package main
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// CopyFile copies the contents of the file named src to the file named
+// by dst. The file will be created if it does not already exist. If the
+// destination file exists, all it's contents will be replaced by the contents
+// of the source file. The file mode will be copied from the source and
+// the copied data is synced/flushed to stable storage.
+func CopyFile(src, dst string) (err error) {
+	in, err := os.Open(src)
+	if err != nil {
+		return
+	}
+	defer in.Close()
+
+	out, err := os.Create(dst)
+	if err != nil {
+		return
+	}
+	defer func() {
+		if e := out.Close(); e != nil {
+			err = e
+		}
+	}()
+
+	_, err = io.Copy(out, in)
+	if err != nil {
+		return
+	}
+
+	err = out.Sync()
+	if err != nil {
+		return
+	}
+
+	si, err := os.Stat(src)
+	if err != nil {
+		return
+	}
+	err = os.Chmod(dst, si.Mode())
+	if err != nil {
+		return
+	}
+
+	return
+}
+
+// CopyDir recursively copies a directory tree, attempting to preserve permissions.
+// Source directory must exist, destination directory must *not* exist.
+// Symlinks are ignored and skipped.
+func CopyDir(src string, dst string) (err error) {
+	src = filepath.Clean(src)
+	dst = filepath.Clean(dst)
+
+	si, err := os.Stat(src)
+	if err != nil {
+		return err
+	}
+	if !si.IsDir() {
+		return fmt.Errorf("source is not a directory")
+	}
+
+	_, err = os.Stat(dst)
+	if err != nil && !os.IsNotExist(err) {
+		return
+	}
+	if err == nil {
+		return fmt.Errorf("destination already exists")
+	}
+
+	err = os.MkdirAll(dst, si.Mode())
+	if err != nil {
+		return
+	}
+
+	entries, err := ioutil.ReadDir(src)
+	if err != nil {
+		return
+	}
+
+	for _, entry := range entries {
+		srcPath := filepath.Join(src, entry.Name())
+		dstPath := filepath.Join(dst, entry.Name())
+
+		if entry.IsDir() {
+			err = CopyDir(srcPath, dstPath)
+			if err != nil {
+				return
+			}
+		} else {
+			// Skip symlinks.
+			if entry.Mode()&os.ModeSymlink != 0 {
+				continue
+			}
+
+			err = CopyFile(srcPath, dstPath)
+			if err != nil {
+				return
+			}
+		}
+	}
+
+	return
+}

go.mod

@@ -0,0 +1,3 @@
+module update
+
+go 1.23.0

post_backup.hook

@@ -0,0 +1,11 @@
+[Trigger]
+Operation = Install
+Operation = Upgrade
+Operation = Remove
+Type = Path
+Target = /usr/local/bin/backup
+
+[Action]
+Description = Backing up the pacman db...
+When = PostTransaction
+Exec = /usr/local/bin/backup post

pre_backup.hook

@@ -0,0 +1,12 @@
+[Trigger]
+Operation = Install
+Operation = Upgrade
+Operation = Remove
+Type = Path
+Target = /usr/local/bin/backup
+
+[Action]
+Description = Backing up the pacman db...
+When = PreTransaction
+Exec = /usr/local/bin/backup pre
+AbortOnFail