Fix doc and user create script to set homedir permissions

RHEL based distros set homedir permissions to 700,
and Ubuntu 21.04+ to 750[1], i.e missing executable
permission for group or others, this results into failures
as defined in the below bug.

Since in doc we add useradd command, it's good to
add instructions to fix the permissions there itself
instead of getting failures during installation and then
fixing it.

Also update user create script to fix permissions
by adding executable bit to DEST directory if missing.

[1] https://discourse.ubuntu.com/t/private-home-directories-for-ubuntu-21-04-onwards/19533

Closes-Bug: #1966858
Change-Id: Id2787886433281238eb95ee11a75eddeef514293

doc/source/guides/multinode-lab.rst

@@ -75,6 +75,14 @@ Otherwise create the stack user:
 
     useradd -s /bin/bash -d /opt/stack -m stack
 
+Ensure home directory for the ``stack`` user has executable permission for all,
+as RHEL based distros create it with ``700`` and Ubuntu 21.04+ with ``750``
+which can cause issues during deployment.
+
+::
+
+    chmod +x /opt/stack
+
 This user will be making many changes to your system during installation
 and operation so it needs to have sudo privileges to root without a
 password:

doc/source/guides/single-machine.rst

@@ -49,6 +49,14 @@ below)
 
     $ sudo useradd -s /bin/bash -d /opt/stack -m stack
 
+Ensure home directory for the ``stack`` user has executable permission for all,
+as RHEL based distros create it with ``700`` and Ubuntu 21.04+ with ``750``
+which can cause issues during deployment.
+
+.. code-block:: console
+
+    $ sudo chmod +x /opt/stack
+
 Since this user will be making many changes to your system, it will need
 to have sudo privileges:
 

doc/source/index.rst

@@ -57,6 +57,14 @@ to run DevStack with
 
    $ sudo useradd -s /bin/bash -d /opt/stack -m stack
 
+Ensure home directory for the ``stack`` user has executable permission for all,
+as RHEL based distros create it with ``700`` and Ubuntu 21.04+ with ``750``
+which can cause issues during deployment.
+
+.. code-block:: console
+
+    $ sudo chmod +x /opt/stack
+
 Since this user will be making many changes to your system, it should
 have sudo privileges:
 

tools/create-stack-user.sh

@@ -44,6 +44,15 @@ fi
 if ! getent passwd $STACK_USER >/dev/null; then
     echo "Creating a user called $STACK_USER"
     useradd -g $STACK_USER -s /bin/bash -d $DEST -m $STACK_USER
+    # RHEL based distros create home dir with 700 permissions,
+    # And Ubuntu 21.04+ with 750, i.e missing executable
+    # permission for either group or others
+    # Devstack deploy will have issues with this, fix it by
+    # adding executable permission
+    if [[ $(stat -c '%A' $DEST|grep -o x|wc -l) -lt 3 ]]; then
+        echo "Executable permission missing for $DEST, adding it"
+        chmod +x $DEST
+    fi
 fi
 
 echo "Giving stack user passwordless sudo privileges"