btrfs-map-physical's Introduction

btrfs-map-physical

Tool to calculate resume_offset for btrfs

Copied from osandov-linux without the rest of the scripts I don't need

Instructions for hibernation

Compile with make all
run ./btrfs_map_physical /path/to/swapfile

Example output:

FILE OFFSET  EXTENT TYPE  LOGICAL SIZE  LOGICAL OFFSET  PHYSICAL SIZE  DEVID  PHYSICAL OFFSET
0            regular      4096          2927632384      268435456      1      4009762816
4096         prealloc     268431360     2927636480      268431360      1      4009766912
268435456    prealloc     268435456     3251634176      268435456      1      4333764608
536870912    prealloc     268435456     3520069632      268435456      1      4602200064
805306368    prealloc     268435456     3788505088      268435456      1      4870635520
1073741824   prealloc     268435456     4056940544      268435456      1      5139070976
1342177280   prealloc     268435456     4325376000      268435456      1      5407506432
1610612736   prealloc     268435456     4593811456      268435456      1      5675941888

Note the first physical offset returned by this tool. In this example, we use 4009762816
Get the pagesize with getconf PAGESIZE
To compute the resume_offset value, divide the physical offset by the pagesize. In this example, it is 4009762816 / 4096 = 978946
Set the resume=swap_device and resume_offset=swap_file_offset kernel parameters. For example, for grub: Add GRUB_CMDLINE_LINUX="resume=UUID=ROOT_UUID resume_offset=RESUME_OFFSET" in /etc/default/grub and then regenerate the grub configuration.

See Arch Wiki for more information

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