feat: Add MR_USER_BASE environment variable to override system-wide d…

…efault for runners' local users base directory

README.md

@@ -26,6 +26,7 @@ Environment variables:
   MR_GIHUB_BASEURL=https://github.com
   MR_GIHUB_API_BASEURL=https://api.github.com
   MR_RELEASE_URL=<latest on github.com/actions/runner/releases>
+  MR_USER_BASE=/home
   MR_GITHUB_PAT=github_pat_***
 
 Sub-commands:
@@ -45,7 +46,6 @@ Options:
   --org     GitHub organization name
   --repo    GitHub repository name, registration on organization-level if empty
   --user    Linux local username of runner
-  --base    Base directory for user home directories
   --labels  Extra labels for the runner
   --group   Runner group for the runner
   --token   Runner registration token, takes precedence over MR_GITHUB_PAT
@@ -118,6 +118,8 @@ To setup multi-runners, you can simplify run following command multi times:
 ./mr.bash add --org <ORG-NAME-2>
 ```
 
+This application will create one Linux local user for one runner via `useradd` command. The *Base Directory* of these users is read from `HOME` setting in your `/etc/default/useradd` file by default (typically `/home`). You can also set it in environment variable `MR_USER_BASE` to override system-wide default.
+
 ### List all runners on current host
 
 This application also integrated status check of runners.

mr.bash

@@ -26,6 +26,8 @@ declare -rg MR_GIHUB_API_BASEURL="${MR_GIHUB_API_BASEURL:-https://api.github.com
 declare -rg MR_GIHUB_BASEURL="${MR_GIHUB_BASEURL:-https://github.com}"
 # runners' local username prefix, defaults to `runner-`
 declare -rg MR_USER_PREFIX="${MR_USER_PREFIX:-runner-}"
+# runners' local users base directory, overrides the `HOME` setting in `/etc/default/useradd`
+declare -rg MR_USER_BASE="${MR_USER_BASE:-$(useradd -D | grep '^HOME=' | cut -d= -f2-)}"
 # URL of this application
 declare -rg MR_URL='https://github.com/vbem/multi-runners'
 
@@ -153,7 +155,7 @@ function mr::addUser {
     run::logFailed sudo tee /etc/sudoers.d/runners <<<'%runners ALL=(ALL) NOPASSWD:ALL' >/dev/null \
         && run::logFailed sudo groupadd -f 'runners' >&2 \
         && run::logFailed sudo groupadd -f 'docker' >&2 \
-        && run::log sudo useradd -b "${base:-/home}" -m -s /bin/bash -G 'runners,docker' "$user" >&2 || return $?
+        && run::log sudo useradd -b "$MR_USER_BASE" -m -s /bin/bash -G 'runners,docker' "$user" >&2 || return $?
     echo "$user"
 }
 
@@ -318,6 +320,7 @@ Environment variables:
   MR_GIHUB_BASEURL=$MR_GIHUB_BASEURL
   MR_GIHUB_API_BASEURL=$MR_GIHUB_API_BASEURL
   MR_RELEASE_URL=${MR_RELEASE_URL:-<latest on github.com/actions/runner/releases>}
+  MR_USER_BASE=$MR_USER_BASE
   MR_GITHUB_PAT=${MR_GITHUB_PAT::11}${MR_GITHUB_PAT:+***}
 
 Sub-commands:
@@ -337,7 +340,6 @@ Options:
   --org     GitHub organization name
   --repo    GitHub repository name, registration on organization-level if empty
   --user    Linux local username of runner
-  --base    Base directory for user home directories
   --labels  Extra labels for the runner
   --group   Runner group for the runner
   --token   Runner registration token, takes precedence over MR_GITHUB_PAT
@@ -353,7 +355,7 @@ function mr::main {
     local org='' repo='' user='' labels='' token='' group='' dotenv=''
 
     # parse options into variables
-    getopt_output="$(getopt -o h -l help,org:,repo:,base:,user:,labels:,token:,group:,dotenv: -n "$FILE_THIS" -- "$@")"
+    getopt_output="$(getopt -o h -l help,org:,repo:,user:,labels:,token:,group:,dotenv: -n "$FILE_THIS" -- "$@")"
     log::failed $? "getopt failed!" || return $?
     eval set -- "$getopt_output"
 
@@ -372,10 +374,6 @@ function mr::main {
             user="$2"
             shift 2
             ;;
-        --base)
-            base="$2"
-            shift 2
-            ;;
         --labels)
             labels="$2"
             shift 2