github.com/anonymouse64/snapd@v0.0.0-20210824153203-04c4c42d842d/boot/booted_kernel_partition_linux.go (about) 1 // -*- Mode: Go; indent-tabs-mode: t -*- 2 3 /* 4 * Copyright (C) 2020 Canonical Ltd 5 * 6 * This program is free software: you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 3 as 8 * published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program. If not, see <http://www.gnu.org/licenses/>. 17 * 18 */ 19 20 package boot 21 22 import ( 23 "fmt" 24 "strings" 25 26 "github.com/snapcore/snapd/bootloader/efi" 27 ) 28 29 const ( 30 // note the vendor ID 4a67b082-0a4c-41cf-b6c7-440b29bb8c4f is systemd, this 31 // variable is populated by shim 32 loaderDevicePartUUID = "LoaderDevicePartUUID-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f" 33 ) 34 35 // FindPartitionUUIDForBootedKernelDisk returns the partition uuid for the 36 // partition that the booted kernel is located on. 37 func FindPartitionUUIDForBootedKernelDisk() (string, error) { 38 // try efi variables first 39 partuuid, _, err := efi.ReadVarString(loaderDevicePartUUID) 40 if err == nil { 41 // the LoaderDevicePartUUID is in all caps, but lsblk, 42 // etc. use lower case so for consistency just make it 43 // lower case here too 44 return strings.ToLower(partuuid), nil 45 } 46 if err == efi.ErrNoEFISystem { 47 return "", err 48 } 49 50 // TODO:UC20: use the kernel command line parameter from the little kernel 51 // bootloader if we have a littlekernel bootloader 52 53 // TODO:UC20: add more fallbacks here, even on amd64, when we don't have efi 54 // i.e. on bios? 55 return "", fmt.Errorf("could not find partition uuid for booted kernel: %v", err) 56 }