Allow for config drop-ins

Enhancement to /etc/enroot/enroot.conf:
If the directory /etc/enroot/enroot.conf.d exisits,
also load all files named *.conf in the same manner as the .conf file
in asciicographical order (modulo LC_COLLATE)

Signed-off-by: Tobias Pape <tobias@netshed.de>

Author: krono

Makefile

@@ -38,7 +38,9 @@ UTILS := bin/enroot-aufs2ovlfs    \
          bin/enroot-switchroot    \
          bin/enroot-nsenter
 
-CONFIG := conf/enroot.conf
+CONFIGFILE := enroot.conf
+CONFIG := conf/$(CONFIGFILE)
+CONFIGINFO := conf/$(CONFIGFILE).d/README
 
 HOOKS := conf/hooks/10-aptfix.sh   \
          conf/hooks/10-cgroups.sh  \
@@ -125,7 +127,7 @@ depsclean:
 
 install: all
 	install -d -m 755 $(SYSCONFDIR) $(LIBDIR) $(BINDIR) $(DATADIR)
-	install -d -m 755 $(addprefix $(SYSCONFDIR)/, environ.d mounts.d hooks.d)
+	install -d -m 755 $(addprefix $(SYSCONFDIR)/, environ.d mounts.d hooks.d $(CONFIGFILE).d)
 	install -d -m 755 $(addprefix $(DATADIR)/, environ.d mounts.d hooks.d)
 	install -m 644 $(ENVIRON) $(SYSCONFDIR)/environ.d
 	install -m 644 $(MOUNTS) $(SYSCONFDIR)/mounts.d
@@ -134,6 +136,7 @@ install: all
 	install -m 644 $(MOUNTS_EXTRA) $(DATADIR)/mounts.d
 	install -m 644 $(CONFIG_EXTRA) $(DATADIR)
 	install -m 644 $(CONFIG) $(SYSCONFDIR)
+	install -m 644 $(CONFIGINFO) $(SYSCONFDIR)/$(CONFIGFILE).d
 	install -m 644 $(SRCS) $(LIBDIR)
 	install -m 755 $(BIN) $(UTILS) $(DEPS) $(BINDIR)
 

conf/enroot.conf.d/README

@@ -0,0 +1,12 @@
+# Drop-ins for enroot.conf
+#
+# All files in this directory named *.conf are read in shell expansion order
+# (ie, asciicographical, possibly influenced by LC_COLLATE)
+#
+# Any file to be processed must adhere to the same format as enroot.conf.
+# See there for details.
+#
+# If necessary, a numbering scheme (10-default.conf, 20-local.conf, 30-....conf)
+# might be beneficial.
+#
+# EOF

doc/configuration.md

@@ -17,6 +17,7 @@ The following table describes standard paths used by the runtime:
 | `ENROOT_DATA_PATH` | `${XDG_DATA_HOME}/enroot` | Path to user container storage |
 | `ENROOT_TEMP_PATH` | `${TMPDIR}` | Path to temporary directory |
 
+When `enroot.conf` has been read, and if there is a directory `enroot.conf.d` next to `enroot.conf`, all files in that directory matching `*.conf` will be considered, too.
 
 ## Container configuration
 

enroot.in

@@ -28,7 +28,7 @@ config::export() {
     [ -n "${3-}" ] && export "$1=$2" || export "$1=${!1:-$2}"
 }
 
-config::init() {
+config::load() {
     local -r file="$1" overwrite="${2-}"
 
     if [ -s "${file}" ] && ! "${BASH}" -n "${file}" > /dev/null 2>&1; then
@@ -47,6 +47,19 @@ config::init() {
    fi
 }
 
+config::init() {
+    local -r file="$1" overwrite="${2-}"
+
+    config::load "${file}" "${overwrite}"
+    if [ -d "${file}.d" ]; then
+      shopt -s nullglob
+      for dropin in "${file}.d"/*".conf"; do
+        config::load "${dropin}" "${overwrite}"
+      done
+      shopt -u nullglob
+    fi
+}
+
 config::fini() {
     for var in $(compgen -e "ENROOT_"); do
         if [[ "${!var}" =~ ^(no?|N[oO]?|[fF](alse)?|FALSE)$ ]]; then