improving /etc/exports construction from environment variables

Author: ehough

README.md

@@ -24,7 +24,7 @@ This is the only containerized NFS server that offers **all** of the following f
 
 The container requires you to supply it with your desired [NFS exports](https://linux.die.net/man/5/exports) upon startup. You have **two choices** for doing this:
 
-1. **Bind mount an exports file into the container at `/etc/exports`**.
+1. **Bind mount a full exports file into the container at `/etc/exports`**.
 
        docker run \
          -v /host/path/to/exports.txt:/etc/exports:ro \
@@ -33,15 +33,15 @@ The container requires you to supply it with your desired [NFS exports](https://
          -p 2049:2049 \
          erichough/nfs4-server:latest`
          
-1. **Supply environment variable triplets to the container to allow it to construct `/etc/exports`**.
+1. **Supply each line of `/etc/exports` as an environment variable**.
 
-    Each triplet should consist of `NFS_EXPORT_DIR_*`, `NFS_EXPORT_CLIENT_*`, and `NFS_EXPORT_OPTIONS_*`. You can add as many triplets as you'd like.
+    The container will look for environment variables that start with `NFS_EXPORT_` and end with an integer. e.g. `NFS_EXPORT_0`, `NFS_EXPORT_1`, etc.
 
        docker run \
-         -e NFS_EXPORT_DIR_0=/nfs \
-         -e NFS_EXPORT_CLIENT_0=192.168.1.0/24 \
-         -e NFS_EXPORT_OPTIONS_0=rw,no_subtree_check,fsid=0 \
-         -v /host/files:/nfs \
+         -e NFS_EXPORT_0='/nfs/foo 192.168.1.0/24(ro,no_subtree_check)' \
+         -e NFS_EXPORT_1='/nfs/bar 123.123.123.123/32(rw,no_subtree_check)' \
+         -v /host/path/foo:/nfs/foo \
+         -v /host/path/bar:/nfs/bar \
          --cap-add SYS_ADMIN \
          -p 2049:2049 \
          erichough/nfs4-server:latest`

entrypoint.sh

@@ -246,54 +246,48 @@ init_trap() {
   trap stop SIGTERM SIGINT
 }
 
-init_exports()
-{
+init_exports() {
+
   if mount | grep -Eq '^[^ ]+ on /etc/exports type '; then
     log '/etc/exports appears to be mounted via Docker'
     return
   fi
 
   local collected=0
   local exports=''
-  local candidateDirs
+  local candidateExportVariables
 
-  candidateDirs=$(compgen -A variable | grep -E 'NFS_EXPORT_DIR_[0-9]*')
-  exit_on_failure 'missing NFS_EXPORT_DIR_* environment variable(s)'
+  candidateExportVariables=$(compgen -A variable | grep -E 'NFS_EXPORT_[0-9]+' | sort)
+  exit_on_failure 'please bind mount /etc/exports or supply NFS_EXPORT_* environment variables'
 
   log 'building /etc/exports'
 
-  for dir in $candidateDirs; do
+  for exportVariable in $candidateExportVariables; do
 
-    local index=${dir##*_}
-    local net=NFS_EXPORT_CLIENT_$index
-    local opt=NFS_EXPORT_OPTIONS_$index
+    local line=${!exportVariable}
+    local lineAsArray
+    IFS=' ' read -r -a lineAsArray <<< "$line"
+    local dir="${lineAsArray[0]}"
 
-    if [[ ! -d "${!dir}" ]]; then
-      log "skipping $dir (${!dir}) since it is not a directory"
+    if [[ ! -d "$dir" ]]; then
+      log "skipping $line since $dir is not a directory"
       continue
     fi
 
-    if [[ -n ${!net} ]] && [[ -n ${!opt} ]]; then
-
-      log "will export ${!dir} to ${!net} with options ${!opt}"
+    log "will export $line"
 
-      local line="${!dir} ${!net}(${!opt})"
-
-      if [[ $collected -gt 0 ]]; then
-        exports=$exports$'\n'
-      fi
+    if [[ $collected -gt 0 ]]; then
+      exports=$exports$'\n'
+    fi
 
-      exports=$exports$line
+    exports=$exports$line
 
-      (( collected++ ))
+    (( collected++ ))
 
-     else
-        log "skipping $dir (${!dir}) as it is missing domain and/or options. be sure to set both $net and $opt."
-     fi
   done
 
   if [[ $collected -eq 0 ]]; then
-    log 'no directories to export.'
+    log 'no valid exports'
     exit 1
   fi