diff --git a/README.md b/README.md
index 50a7a7c..bf636cb 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,21 @@
 # TrueNAS_change_arc_size
-Simple script for checking if arc size was changed.
+Script for checking if arc size was changed, and changing it back. 
+
+
+## Usage
+Set **arc_check.sh** file to run with cron, InitScript or both.
+
+In **arc_check.sh** change ***<CHANGE_ME>*** value to match the size you want. For converting GiB to bytes I've used [this site](https://www.dataunitconverter.com/gibibyte-to-byte). 
+
+
+### Crontab
+**1>** redirects stdout to /tmp/arc_size.log
+
+**2>** stderr to /tmp/arc_size.errlog
+
+<_cronexpression_> /dir/to/file/arc_check.sh 1> /tmp/arc_size.log 2> /tmp/arc_size.errlog
+
+
+### InitScript
+
+You can configure it in TrueNAS GUI under System Settings > Advanced > Init/Shutdown Scripts
\ No newline at end of file
diff --git a/arc_check.sh b/arc_check.sh
new file mode 100644
index 0000000..93ebeef
--- /dev/null
+++ b/arc_check.sh
@@ -0,0 +1,21 @@
+#!/usr/bin/zsh
+
+arc_size=$(cat "/sys/module/zfs/parameters/zfs_arc_max")
+
+target_arc_size="<CHANGE_ME>"  # GiB to bytes | ex. 24GiB = 25769803776
+
+if [[ -z $arc_size || $arc_size -eq "0" || $arc_size -lt "0" ]]
+then
+    echo "<CHANGE_ME>" >> /sys/module/zfs/parameters/zfs_arc_max
+    echo "Arc size changed!"
+    exit 1
+
+elif [[ $arc_size = $target_arc_size ]]
+then
+    echo "Arc size is set properly."
+    exit 0
+
+else
+    echo "Unknown state!"
+    exit 1
+fi