diff --git a/.vscode/settings.json b/.vscode/settings.json
index 2a8db89..33c6c6d 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -126,6 +126,7 @@
         "userspace",
         "winget",
         "wlan",
+        "xattr",
         "zstd"
     ],
     "markdown.extension.toc.levels": "2..6",
diff --git a/knowledge base/acl.md b/knowledge base/acl.md
index eda7495..cb32301 100644
--- a/knowledge base/acl.md	
+++ b/knowledge base/acl.md	
@@ -4,11 +4,17 @@
 
 1. [TL;DR](#tldr)
 1. [Set default permissions for files and directories](#set-default-permissions-for-files-and-directories)
+   1. [Posix](#posix)
+   1. [NFSv4](#nfsv4)
 1. [Further readings](#further-readings)
 
 ## TL;DR
 
-List of [permission tags][syntax descriptions for setting acls] and [inheritance options][acl inheritance].
+When **setting** permissions, the _execute_ flag can be set to the **uppercase** `X` instead of the **lowercase** `x`.<br/>
+The uppercase `X` permission allows execution only if the target is a directory or if the execute permission has already been set for the user or group.
+
+BSD systems use NFSv4 ACLs by default in ZFS.
+List of **NFSv4** [permission tags][syntax descriptions for setting acls] and [inheritance options][acl inheritance].
 
 ```sh
 # Install the tool.
@@ -16,49 +22,86 @@ apt install 'acl'
 dnf install 'acl'
 
 # Show ACLs.
-getfacl 'test/declarations.h'
+getfacl 'path/to/file'
 
 # Set permissions for users.
-setfacl -m 'u:username:rwx' 'test/declarations.h'
+setfacl -m 'u::r-x' 'path/to/file'
+setfacl -m 'u::rwX' 'path/to/dir'
+setfacl -m 'u:username:r-x' 'path/to/file'
+setfacl -m 'u:username:rwX' 'path/to/dir'
 
 # Add permissions for users.
 # Position number starts from 0.
-setfacl -a '1' 'u:username:rwx' 'test/declarations.h'
-setfacl -a '5' 'owner@:rw-p-daARWcCos:f------:allow' 'path/to/file'
-setfacl -a '6' 'owner@:rwxpDdaARWcCos:-d-----:allow' 'path/to/dir'
+setfacl -a '1' 'u:username:rwx' 'path/to/file'
+setfacl -a '2' 'u::rwX' 'path/to/dir'
+setfacl -a '5' 'owner@:rw-p-daARWcCos::allow' 'path/to/file'
+setfacl -a '6' 'owner@:rwxpDdaARWcCos::allow' 'path/to/dir'
 
 # Set permissions for groups.
-setfacl -m "g:groupname:r-x" 'test/declarations.h'
+setfacl -m 'g::r-x' 'path/to/file'
+setfacl -m 'g::rw-' 'path/to/dir'
+setfacl -m 'g:username:r-x' 'path/to/file'
+setfacl -m 'g:username:rwX' 'path/to/dir'
 
 # Add permissions for groups.
 # Position number starts from 0.
-setfacl -a '2' 'g:groupname:r-x' 'test/declarations.h'
-setfacl -a '7' 'group@:r--p--aAR-c--s:f------:allow' 'path/to/file'
-setfacl -a '8' 'group@:r-xp--aAR-c--s:-d-----:allow' 'path/to/dir'
+setfacl -a '2' 'g:groupname:r-x' 'path/to/file'
+setfacl -a '4' 'g::rw-' 'path/to/dir'
+setfacl -a '7' 'group@:r--p--aAR-c--s::allow' 'path/to/file'
+setfacl -a '8' 'group@:r-xp--aAR-c--s::allow' 'path/to/dir'
 
 # Add permissions for everyone else (others).
 # Position number starts from 0.
-setfacl -a '3' 'o::r-x' 'test/declarations.h'
-setfacl -a '9'  'everyone@:r-----a-R-c---:f------:allow' 'path/to/file'
-setfacl -a '10' 'everyone@:r-x---a-R-c---:-d-----:allow' 'path/to/dir'
+setfacl -a '3' 'o::r-x' 'path/to/file'
+setfacl -a '3' 'o::r-X' 'path/to/dir'
+setfacl -a '9'  'everyone@:r-----a-R-c---::allow' 'path/to/file'
+setfacl -a '10' 'everyone@:r-x---a-R-c---::allow' 'path/to/dir'
+
+# Change multiple permissions in one command.
+setfacl -m 'u::rw,g::r' 'path/to/file'
+setfacl -m 'u::rwX,g::rwX,o::rx' 'path/to/dir'
 
 # Make children files and directories inherit acls.
-# A.K.A. sets default ACLs.
-setfacl -d -m 'u:dummy:rw' 'test'
+# A.K.A. set 'default' ACLs.
+setfacl -dm 'u:dummy:rw' 'path/to/file'
+setfacl -m 'default:u::rwX,g::rX,o:r' 'path/to/dir'
+setfacl -a '11'    'group@:r-----a-R-c---:f------:allow' 'path/to/file'
+setfacl -a '12' 'everyone@:r-x---a-R-c---:-d-----:allow' 'path/to/dir'
 
 # Remove specific acls.
 setfacl -x 'u:dummy:rw' 'test'
 
 # Remove all ACL entries except for the ones synthesized from the file mode.
 # If a 'mask' entry was in them, the resulting ACLs will be set accordingly.
-setfacl -b 'test/declarations.h'
+setfacl -b 'path/to/file'
 ```
 
 ## Set default permissions for files and directories
 
-Suppose you want a folder to set the default permissions of newly created files and directories to `0664` (`-rw-rw-r--`) and `0775` (`drwxrwxr-x`) respectively.
+Suppose you want a folder to set the default permissions of newly created files and directories to `0664` (`-rw-rw-r--`) and `0775` (`drwxrwxr-x`) respectively.<br/>
+The best way to achieve this would be to set up it's ACLs accordingly.
 
-The best way to achieve this would be to set up it's ACLs accordingly:
+### Posix
+
+| Who   | ACL Type | Permissions          | Flags             | Translated `getfacl` Tags | Resulting Unix Permissions |
+| ----- | -------- | -------------------- | ----------------- | ------------------------- | -------------------------- |
+| user  | Allow    | Read, Write          | File Inherit      | `default:user::rw-`       | `-rw-------`               |
+| user  | Allow    | Read, Write, Execute | Directory Inherit | `default:user::rwX`       | `drwx------`               |
+| group | Allow    | Read, Write          | File Inherit      | `default:group::rw-`      | `----rw----`               |
+| group | Allow    | Read, Write, Execute | Directory Inherit | `default:group::rwX`      | `d---rwx---`               |
+| other | Allow    | Read, Write          | File Inherit      | `default:other::rw-`      | `-------rw-`               |
+| other | Allow    | Read, Write, Execute | Directory Inherit | `default:other::rwX`      | `d------rwx`               |
+
+```sh
+setfacl -dm 'u::rwX' 'path/to/dir'
+setfacl -dm 'g::rwX' 'path/to/dir'
+setfacl -dm 'o::r-X' 'path/to/dir'
+
+# Or, in one go.
+setfacl -dm 'u::rwX,g::rwX,o::rX' 'path/to/dir'
+```
+
+### NFSv4
 
 | Who       | ACL Type | Permissions                                                                                                                                                                                                             | Flags             | Translated `getfacl` Tags                | Resulting Unix Permissions |
 | --------- | -------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------- | ---------------------------------------- | -------------------------- |
@@ -70,8 +113,6 @@ The best way to achieve this would be to set up it's ACLs accordingly:
 | everyone@ | Allow    | Read Data<br/>Read Named Attributes<br/>Execute<br/>Read Attributes<br/>Read ACL                                                                                                                                        | Directory Inherit | `everyone@:r-x---a-R-c---:-d-----:allow` | `d------r-x`               |
 
 ```sh
-# Set default permissions of '0664' for files and '0775' for directories.
-# Includes ACL-type permissions accordingly.
 setfacl -m        'owner@:rw-p-daARWcCos:f------:allow' 'path/to/dir'
 setfacl -a '1'    'owner@:rwxpDdaARWcCos:-d-----:allow' 'path/to/dir'
 setfacl -m        'group@:r--p--aAR-c--s:f------:allow' 'path/to/dir'
diff --git a/knowledge base/diy nas/v1.md b/knowledge base/diy nas/v1.md
index 94c8ae2..64da08a 100644
--- a/knowledge base/diy nas/v1.md	
+++ b/knowledge base/diy nas/v1.md	
@@ -21,12 +21,17 @@
 
 ## Software
 
-| Component        | Choice           | Notes                                              |
-| ---------------- | ---------------- | -------------------------------------------------- |
-| Operating system | [OpenMediaVault] | With [OMV-Extras](../openmediavault.md#omv-extras) |
-| Kernel           | Default (Debian) |                                                    |
-| OS file system   | Default (ext4)   |                                                    |
-| Data file system | ZFS              | See [ZFS](../openmediavault.md#zfs)                |
+| Component        | Choice           | Notes                                                 |
+| ---------------- | ---------------- | ----------------------------------------------------- |
+| Operating system | [OpenMediaVault] | With [OMV-Extras](../openmediavault.md#omv-extras)    |
+| Kernel           | Default (Debian) |                                                       |
+| OS file system   | Default (ext4)   |                                                       |
+| Data file system | ZFS              | See [ZFS on OpenMediaVault](../openmediavault.md#zfs) |
+
+ZFS datasets used as shared folders shall have the following properties:
+- `aclinherit:restricted`;
+- `aclmode:groupmask`;
+- `acltype:posix` + `xattr:sa` until `nfsv4` is supported on Linux.
 
 ## Further readings
 
diff --git a/knowledge base/openmediavault.md b/knowledge base/openmediavault.md
index 79e6304..47dc059 100644
--- a/knowledge base/openmediavault.md	
+++ b/knowledge base/openmediavault.md	
@@ -171,6 +171,7 @@ Just enable property in the pool or dataset.
 - [Proxmox]
 - [OMV-Extras]
 - [Disks maintenance]
+- [ZFS]
 
 ## Sources
 
@@ -198,6 +199,7 @@ All the references in the [further readings] section, plus the following:
 [debian]: debian.md
 [disks maintenance]: disks%20maintenance.md
 [proxmox]: proxmox.md
+[zfs]: zfs.md
 
 <!-- Others -->
 [hdparm]: https://linux.die.net/man/8/hdparm