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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2015 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package partition
import (
"bufio"
"errors"
"os"
"path/filepath"
"strings"
)
const (
bootBase = "/boot"
ubootDir = bootBase + "/uboot"
grubDir = bootBase + "/grub"
ubootConfigFile = ubootDir + "/snappy-system.txt"
grubConfigFile = grubDir + "/grubenv"
)
var (
// dependency aliasing
filepathGlob = filepath.Glob
// BootSystem proxies bootSystem
BootSystem = bootSystem
configFiles = map[string]string{"uboot": ubootConfigFile, "grub": grubConfigFile}
)
// bootSystem returns the name of the boot system, grub or uboot.
func bootSystem() (string, error) {
matches, err := filepathGlob(bootBase + "/grub")
if err != nil {
return "", err
}
if len(matches) == 1 {
return "grub", nil
}
return "uboot", nil
}
// BootDir returns the directory used by the boot system.
func BootDir(bootSystem string) string {
if bootSystem == "grub" {
return grubDir
}
return ubootDir
}
// NextBootPartition returns the partition the system will use on the next boot
// if we are upgrading. In grub systems it is the partition pointed in the boot
// config file. For uboot systems the boot config file does not change, so that
// we take the other partition in that case
func NextBootPartition() (partition string, err error) {
m, err := mode()
if err != nil {
return
}
if m != "try" {
return "", errors.New("Snappy is not in try mode")
}
snappyab, err := confValue("snappy_ab")
if err != nil || snappyab == "" {
return
}
system, err := BootSystem()
if err != nil {
return
}
if system == "grub" {
// in grub based systems, the boot config file is changed before
// the update has been applied
partition = snappyab
} else {
// in uboot based systems, the boot config file is not changed until
// the update has been applied
partition = OtherPartition(snappyab)
}
return
}
func mode() (mode string, err error) {
return confValue("snappy_mode")
}
func confValue(key string) (partition string, err error) {
system, err := BootSystem()
if err != nil {
return
}
bootConfigFile := configFiles[system]
file, err := os.Open(bootConfigFile)
if err != nil {
return
}
defer file.Close()
reader := bufio.NewReader(file)
scanner := bufio.NewScanner(reader)
for scanner.Scan() {
if strings.HasPrefix(scanner.Text(), key) {
fields := strings.Split(scanner.Text(), "=")
if len(fields) > 1 {
partition = fields[1]
}
return
}
}
return
}
// OtherPartition returns the backup partition, a or b.
func OtherPartition(current string) string {
if current == "a" {
return "b"
}
return "a"
}
// CurrentPartition returns the current partition, a or b.
func CurrentPartition() (partition string, err error) {
partition, err = confValue("snappy_ab")
if err != nil {
return
}
m, err := mode()
if err != nil {
return
}
if m == "try" {
var system string
system, err = BootSystem()
if err != nil {
return
}
if system == "grub" {
// in grub based systems, the boot config file is changed before
// the update has been applied
partition = OtherPartition(partition)
}
}
return
}
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