How to suspend and
"suspend" aka "suspend-to-RAM" aka "STR" aka "sleep" --> store
everything to RAM and stop CPU, harddisk, screen, etc. Machine
still on, power still required although usage is small. Pressing
(usually) the power button will wake up the CPU, which will
restore its state from RAM, and continues. Fatdog64 has supported
suspend since its early days.
"hibernate" aka "suspend-to-Disk" aka "STD" aka "hibernate" -->
store everything to Disk, then power off. Pressing (usually) the
power button will start-up the machine, run the bootloader, load
and run kernel as usual, but the kernel will recognise that it is
"waking up" from "hibernation" and will restore its state from
Disk instead of the usual power-up. Support for hibernation starts
with Fatdog64 721. On older Fatdogs you can also do hibernation if
you update to the latest kernel.
How to perform suspend
1. On terminal, type "echo mem > /sys/power/state
2. Alternative, if you're on a laptop, just close the lid.
Where are these controlled?
is where lid-closing will trigger
is the actual suspend script,
which will suspend the machine.
Suspend usually works. Most the problem
is "failure to wake up" which can be fatal (e.g. screen fails to
wake up: blank screen), or annoying (e.g. wifi fails to wake-up,
requiring restart of network connection). Usually the problem is
bad module. Identify that, and remove that module before suspend,
and then reload (modprobe) that module again after waking up. See
the suspend script above for examples. Or kill some process and
re-start them again upon wake-up. If you still have problems,
you're SOL: suspend is not for you.
How to perform hibernation
Firstly, make sure suspend works. If you can't even make suspend
to work then forget hibernation.
Secondly, you need to have a swap. Either swap partition or swap
file will do. To be safe, make sure that swap partition/swap file
is at least the size of your RAM.
Third, you need to prepare. Waking up from hibernation requires
support the bootloader, so you must be comfortable of editing boot
entries and adding boot parameter.
Fourth, make sure your disk that contains swap partition/swap file
is a disk that can be accessed by the kernel without need for
additional kernel modules or firmware. Don't attempt to do from
If you have a swap partition, take a note of your swap partition.
For example assume it's /dev/sda7
. Then in your boot
loader entry, add a new parameter "resume=/dev/sda7
you're good to go.
If you have a swap file, take a note of the partition that
contains your swap file (e.g. /dev/sda5
), and then run "filefrag
". You will get an output something
# filefrag -v /mnt/sda5/fd64-swap
Filesystem type is: ef53
File size of /mnt/sda5/fd64-swap is 8589934592 (2097152 blocks
of 4096 bytes)
physical_offset: length: expected: flags:
133119: 32768: 98304:
Pay attention to the first row (row 0), and read the
physical_offset. In this example, it's 36864
Then in your boot loader entry, add the following two parameters:
". Then re-boot. This
reboot is required
for swap file; for swap partition you
don't need to reboot first. If you don't reboot, the hibernation
Once rebooted, on terminal you can do this: "echo disk >
1. Resuming from hibernation doesn't require loading the initrd;
because everything (including the initrd) is already stored in the
hibernation (swap) file. If you want faster "resume" from
hibernation, instead of adding the above boot parameters to an
existing boot entry that loads both the kernel and initrd,
consider creating a new boot entry that only loads the kernel with
the given parameter, e.g. (grub2 example: linux /vmlinuz
). When resuming, choose
this entry so your boot loader only loads the kernel (and not
initrd). Of course, if your bootloader and disk is fast, you can
2. If you use multiple swap files, on console type "cat
/proc/swaps" and perform the "filefrag" command on the first swap
file. Your first swap file must be at least the same size as the
3. If you don't like swap or don't usually use swap, but you want
to hibernate, well then create a new swapfile and do all the above
preparation. Before suspending, run the command in terminal "swapon
" and then hibernate. Upon
wake-up, run this: "swapoff /path/to/swapfile/or/device
turn off the swapfile usage.
I heard there is this feature called "hybrid suspend"
where the state is copied to both RAM and Disk; and the the
machine goes to suspend. If power is not lost during the suspend,
it will wake up from RAM which is fast. But if power is lost, it
will wake up from disk just like hibernation. This is good and
cool because I can suspend to RAM and not worry about power lost.
What about compressing the data used for hibernation?
Hibernation is scary because kernel data is stored to
disk, directly. Somebody could steal the disk and do a scan for
password on the hibernation file. I heard you can encrypt the
All the above features require an advanced suspend module (aka
"userspace suspend") - which currently isn't implemented in