Made the above posted script as an init.d script instead. But beware, this init script runs the actual script as normal user - which is NOT recommended. Tested this and it works. The reason is that sometimes when an x session is running and the .xsession-errors file gets rotated, it won't be written to again. So running it at shutdown or reboot should work better.
Script:

#!/bin/sh

### BEGIN INIT INFO
# Provides: /home/$USER/bin/logrotator for .xsession-errors
# Required-Start: $syslog
# Required-Stop:  $syslog
# Default-Start:  0 6
# Default-Stop:   3 4 5
# Description: Rotate .xsession-errors as user $USER, creates backups. Should run at shutdown only without X
### END INIT INFO

#. /lib/lsb/init-functions

case "$1" in
  start)
	touch /run/logrotator.pid
	chmod 600 /run/logrotator.pid
	chown $USER:65534 /run/logrotator.pid
	sudo -u $USER /home/$USER/bin/logrotator
	;;
 stop)
	killall logrotator
        ;;
  *)
        echo "Usage: $SCRIPTNAME start" >&2
        exit 3
        ;;
esac

Actual script (home/$USER/bin/logrotator):

#!/bin/bash
for i in {9..1}; do
    if [[ -f /home/$USER/.xsession-errors.${i} ]]; then
        mv -f /home/$USER/.xsession-errors.${i} /home/$USER/.xsession-errors.$((i+1))
    fi
done
mv -f /home/$USER/.xsession-errors /home/$USER/.xsession-errors.1
touch /home/$USER/.xsession-errors
##Might not be needed:
chown $USER:$GROUP /home/$USER/.xsession-errors

Edit $USER and $GROUP to taste.

PS. As you can see, I do not know what I'm doing, so don't try this at home.

Oops! On my other Devuan machine .xsession-errors was 830MB!!! But I thought I share my findings for a solution of the growing file size (not the errors )

Create a file like this in /etc/logrotate.d/my-xsession-errors

$HOME/.xsession-errors {
missingok 
notifempty 
copytruncate
compress  
weekly  
rotate 5
}

This will rotate the file weekly and keep 5 old files. Edit to your needs.

EDIT: added copytruncate because sometimes when the .xsession-errors file get renewed, it is not written to anymore (in that session).

Thanks for this thread! My .xsession-errors was 26 Mb. Big! Mostly BS, some GTK errors, the weather applet complaining, xdotool missing for some old script.

I chose ralph.ronnquist's no 2 script and running it manually for now.

Finally my two brain cells got it! Thank you!

=if(or(B281="Sat";B281="Sun");"0";"1")

(Sry for the very late answer)

Yes it's bad and it has even gotten worse over the years. Gobbling up more and more features. A big blob.

My turning point with Systemd was when it slowed down my surfing by taking over the resolver. Systemd created a lag and it was unacceptable to me. I already knew about its history and Poettering, so since then I've been waiting to transition completely to Devuan.

You need the UUID's of the different disks/partitions. In a terminal as root use the command blkid and note the required UUID's you need. Then , as root, edit the file /etc/fstab and add the needed UUID's.

Example line from /etc/fstab:

UUID=9acd7886-5bd7-4fa4-a7e7-63b80c64f28c /mnt/GAMES	ext4	auto,rw,async,exec,suid,noatime 0       2

In this example it's in reality my partition /dev/sdc3 which is mounted with its UUID in fstab instead.

More about fstab: https://man7.org/linux/man-pages/man5/f … %20enabled.

It's worth the wait. Without question. As I see it, there are some fundamental differences between Debian and Devuan that needs extra care and attention. So I'm happy to wait.

Yeah, but I forgot how to do it. I could possibly unpack debs and unzst them, and then repack them as new debs.

Where can I find good guides on that?

Thanks for the help guys!