From c7cd715221f44a7207ebfc77ca15454d3c453009 Mon Sep 17 00:00:00 2001
From: Cliff Brake <cbrake@bec-systems.com>
Date: Tue, 9 Oct 2018 13:06:41 -0400
Subject: [PATCH] document using musl

---
 conf/local.conf                       |  3 +++
 docs/README.md                        |  7 +++++++
 docs/{init-system.md => libc-init.md} | 22 ++++++++++++++++++----
 3 files changed, 28 insertions(+), 4 deletions(-)
 rename docs/{init-system.md => libc-init.md} (67%)

diff --git a/conf/local.conf b/conf/local.conf
index 1200f9f02..fabb27a01 100644
--- a/conf/local.conf
+++ b/conf/local.conf
@@ -57,3 +57,6 @@ ENABLE_UART = "1"
 #VIRTUAL-RUNTIME_init_manager = "busybox"
 #VIRTUAL-RUNTIME_dev_manager = "busybox-mdev"
 #VIRTUAL-RUNTIME_login_manager = "busybox"
+
+# Uncomment the following to enable musl libc
+#TCLIBC = "musl"
diff --git a/docs/README.md b/docs/README.md
index 2bb446057..0f8e2c42b 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -12,6 +12,13 @@ included for some of them below.
 * [BeagleBone -- todo]()
 * [ODroid-C2 -- todo]()
 
+## Image Configuration
+
+OpenEmbedded supports a wide range of technology choices. Some of these are documented
+below.
+
+* [libc/init system](libc-init.md)
+
 ## Design Choices
 
 * [Superproject Management](superproject-management.md)
diff --git a/docs/init-system.md b/docs/libc-init.md
similarity index 67%
rename from docs/init-system.md
rename to docs/libc-init.md
index 41a7cf98d..2ec88034b 100644
--- a/docs/init-system.md
+++ b/docs/libc-init.md
@@ -1,4 +1,4 @@
-# Init System
+# libc and init system selection
 
 ## Systemd
 
@@ -25,11 +25,21 @@ VIRTUAL-RUNTIME_dev_manager = "busybox-mdev"
 VIRTUAL-RUNTIME_login_manager = "busybox"
 ```
 
-## Comparison of disk spaced used by init systems
+## Libc selection
 
-Systemd takes considerably more space than SysVinit. With a rPI2 build, the following
-are the rootfs sizes for core-image-minimal:
+glibc is the default libc, but musl can also be used by setting the following in
+local.conf:
 
+```
+TCLIBC = "musl"
+```
+
+## Comparison of disk spaced used
+
+* Musl + Busybox init/dev/login
+  * space used in ext4 filesystem on running system using df: 1.9MB
+  * adding sizes of files in image from buildhistory: 1.5MB
+  * number of files in image: 595
 * Busybox init/dev/login
   * space used in ext4 filesystem on running system using df: 3.5MB
   * adding sizes of files in image from buildhistory: 3.1MB
@@ -42,3 +52,7 @@ are the rootfs sizes for core-image-minimal:
   * space used in ext4 filesystem on running system using df: 33.2MB
   * adding sizes of files in image from buildhistory: 22MB
   * number of files in image: 1,806
+
+The space on disc used by a systemd image is much larger than adding the size of
+the files in the image. We're not sure why this is -- perhaps there is filesystem
+overhead for small files.