Ubuntu/Pop!_OS 19.04 Suspend then Hibernate

I have been using Pop!_OS 19.04 on my Dell XPS ‘13 recently and one of the missing features I wanted back was “suspend then hibernate”. systemd supports suspend-then-hibernate but as of now, it only supports native hibernation which is not working on my machine. After a lot of experimentation I have settled on a custom script and configuration to get it working.

If you’re interested in getting it working on your machine, follow these steps to enable it:

1. I assume uswsusp hibernation is already installed and configured on the target machine.

2. Place the provided script somewhere on your file system (I saved it as /usr/local/bin/s2smart):

   #!/bin/bash
      
   echo2 () {
       printf "$1\n"
       echo "$1" > /dev/kmsg
   }
      
   if [[ $EUID -ne 0 ]]; then
       echo "This script must be run as root" 
       exit 1
   fi
      
   hibernate_delay=`cat /etc/systemd/sleep.conf | grep -oP "HibernateDelaySec=\K(\d+)" 2> /dev/null || echo 3600`
   battery_capacity=`cat /sys/class/power_supply/BAT0/capacity 2> /dev/null || echo 0`
      
   if [ $battery_capacity -le 20 ]; then
       hibernate_delay=$(($hibernate_delay/2))
   elif [ $battery_capacity -le 50 ]; then
       hibernate_delay=$(($hibernate_delay/4))
   fi
      
   echo2 "Battery capacity at $battery_capacity%%. Will hibernate after $hibernate_delay seconds."
      
   # Record current time.
   curtime=$(date +%s)
   lock=/tmp/rtchibernate.lock
   echo "$curtime" > $lock
      
   # Entering sleep.
   echo2 "Entering suspend at $curtime. Will resume in $hibernate_delay seconds."
   rtcwake -m no -s $hibernate_delay
   s2ram
      
   # Exited the sleep.
   curtime=$(date +%s)
   sustime=`cat $lock`
   rm $lock
      
   echo2 "Exited suspend mode at $curtime."
      
   # Did we wake up due to the rtc timer above?
   if [ $(($curtime - $sustime)) -ge $hibernate_delay ]; then
       # Sometimes when you have too many cores that are too fast run-parts do mess things up.
       # lets get some sleep ;)
       sleep 2
       # Hibernate (suspend to disk)...
       echo2 "Entering hibernation mode at $curtime..."
       s2disk
       echo2 "Exited hibernation."
   else
       # Cancel the rtc timer and wake up normally.
       rtcwake -m disable
       echo2 "Cancelled RTC resume prematurely."
   fi
      
   echo2 "Suspend or hibernate finished. Welcome back."
   

3. Add the line HibernateDelaySec=3600 into /etc/systemd/sleep.conf and adjust it to whatever your desired delay is.

4. Create a file override.conf in /etc/systemd/system/systemd-suspend-then-hibernate.service.d (create the directory if needed):

   [Service]
   ExecStart=
   ExecStartPre=-/usr/bin/run-parts -v -a pre /usr/lib/systemd/system-sleep
   ExecStart=/usr/local/bin/s2smart
   ExecStartPost=-/usr/bin/run-parts -v --reverse -a post /usr/lib/systemd/system-sleep
   

5. Finally, you will need to enable suspend-then-hibernate on lid close by modifying the /etc/systemd/logind.conf. Make sure the following lines are present and not commented out:

   HandleLidSwitch=suspend-then-hibernate
   HandleLidSwitchExternalPower=suspend-then-hibernate
   

There, hope this helps someone. I did not document all the other steps I took to enable hibernation since those can be found online with ease.