Add systemd service unit to allow overcommitting memory on desktops

Currently, a lot of users report that programs are crashing or hanging
on their desktops. The reason is that newer Firefox and browsers in
general need a lot of virtual memory for security reasons. Therefore,
despite enough memory being available, it requests even more.

Allowing to overcommit memory should fix this.

After long discussion in the group, it was decided to allow to
overcommit memory on desktop machines.

Install it into the graphical target as it’s not needed beforehand.

As overcommitting memory is enabled by default, maybe it should be
reversed, but it currently doesn’t matter.

install.sh

@@ -80,6 +80,7 @@ mkdir -p "$DESTDIR$udev_helperdir"
 
 install_exec make-automaps/make-automaps                 "$DESTDIR$usr_sbindir/make-automaps"
 install_data misc_systemd_units/automount.service        "$DESTDIR$systemdunitdir/automount.service"
+install_data misc_systemd_units/enable_overcommit_memory.service "$DESTDIR$systemdunitdir/enable_overcommit_memory.service"
 install_data misc_systemd_units/gdm.service              "$DESTDIR$systemdunitdir/gdm.service"
 install_data misc_systemd_units/lazy-umount-nfs.service  "$DESTDIR$systemdunitdir/lazy-umount-nfs.service"
 install_exec mkmotd/mkmotd.pl                            "$DESTDIR$usr_sbindir/mkmotd.pl"

misc_systemd_units/enable_overcommit_memory.service

@@ -0,0 +1,13 @@
+[Unit]
+Wants=startup-tags.service
+After=startup-tags.service
+ConditionPathExists=/node/tags/desktop
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/sbin/sysctl vm.overcommit_memory=0
+ExecStop=/usr/sbin/sysctl vm.overcommit_memory=2
+
+[Install]
+WantedBy=graphical.target