power-management: Add section.

src/SUMMARY.md

@@ -30,6 +30,7 @@
       - [AppArmor](./config/security/apparmor.md)
    - [Date and Time](./config/date-time.md)
    - [Kernel](./config/kernel.md)
+   - [Power Management](./config/power-management.md)
    - [Network](./config/network/index.md)
       - [iptables](./config/network/iptables.md)
       - [wpa_supplicant](./config/network/wpa_supplicant.md)

src/config/power-management.md

@@ -0,0 +1,29 @@
+# Power
+
+## Power Management
+
+### acpid
+
+The `acpid` service for [acpid(8)](https://man.voidlinux.org/acpid.8) is
+installed and enabled by default. ACPI events are handled by
+`/etc/acpi/handler.sh`, which uses [zzz(8)](https://man.voidlinux.org/zzz.8) for
+suspend-to-RAM events.
+
+### elogind
+
+The `elogind` service is provided by the `elogind` package. By default,
+[elogind(8)](https://man.voidlinux.org/elogind.8) listens for, and processes,
+ACPI events related to lid-switch activation and the *power*, *suspend* and
+*hibernate* keys. This will conflict with the `acpid` service if it is installed
+and enabled. Either disable `acpid` when enabling `elogind`, or configure
+`elogind` to `ignore` ACPI events in
+[logind.conf(5)](https://man.voidlinux.org/logind.conf.5). There are several
+configuration options, all starting with the keyword `Handle`, that should be
+set to `ignore` to avoid interfering with `acpid`.
+
+## Power Saving
+
+Laptop battery life can be extended by using
+[tlp(8)](https://man.voidlinux.org/tlp.8). To use it, install the `tlp` package,
+and enable the `tlp` service. Refer to [the TLP
+documentation](https://linrunner.de/tlp/) for details.

src/config/session-management.md

@@ -30,16 +30,5 @@ also be one of the mechanisms for rootless [Xorg](./graphical-session/xorg.md).
 To make use of its features, install the `elogind` package and make sure the
 [system D-Bus](#d-bus) is enabled. You might need to log out and in again.
 
-### Troubleshooting
-
 If you're having any issues with `elogind`, [enable](./services/index.md) its
 service, as waiting for a D-Bus activation can lead to issues.
-
-By default, `elogind` listens for and processes ACPI events related to
-lid-switch activation and presses of *power*, *suspend* and *hibernate* keys.
-This will conflict with the [acpid(8)](https://man.voidlinux.org/acpid) service
-if it is installed and enabled. Either disable `acpid` when enabling `elogind`
-or configure `elogind` to `ignore` ACPI events in
-[logind.conf(5)](https://man.voidlinux.org/logind.conf.5). There are several
-configuration options, all starting with the keyword `Handle`, that should be
-set to `ignore` to avoid interfering with `acpid`.