Fix some typos in "Mount MicroCeph backed Block Devices" doc (canonic…

…al#479)

# Description

Fix some typos in "Mount MicroCeph backed Block Devices" tutorial. 

## Type of change

Please delete options that are not relevant.

- [x] Documentation update (Doc only change)

## How Has This Been Tested?

Check the rendered web page from local environment, and made sure the
command works after this change.

```shell
make html
make serve
```

## Contributor's Checklist

Please check that you have:

- [x] self-reviewed the code in this PR.
- [x] updated the user documentation with corresponding changes.

---------

Signed-off-by: Chi Wai Chan <[email protected]>

docs/how-to/mount-block-device.rst

@@ -2,7 +2,7 @@
 Mount MicroCeph backed Block Devices
 ====================================
 
-Ceph RBD (RADOS Block Device) are virtual block devices backed by the Ceph storage cluster. 
+Ceph RBD (RADOS Block Device) are virtual block devices backed by the Ceph storage cluster.
 This tutorial will guide you with mounting Block devices using MicroCeph.
 
 The above will be achieved by creating an rbd image on the MicroCeph deployed
@@ -26,12 +26,12 @@ Check Ceph cluster's status:
     cluster:
         id:     90457806-a798-47f2-aca1-a8a93739941a
         health: HEALTH_OK
-    
+
     services:
         mon: 1 daemons, quorum workbook (age 36m)
         mgr: workbook(active, since 50m)
         osd: 3 osds: 3 up (since 17m), 3 in (since 47m)
-    
+
     data:
         pools:   2 pools, 33 pgs
         objects: 21 objects, 13 MiB
@@ -42,14 +42,14 @@ Create a pool for RBD images:
 
 .. code-block:: none
 
-    $ sudo ceph osd pool create block_pool 
+    $ sudo ceph osd pool create block_pool
     pool 'block_pool' created
 
     $ sudo ceph osd lspools
     1 .mgr
     2 block_pool
 
-    $ rbd pool init block_pool
+    $ sudo rbd pool init block_pool
 
 Create RBD image:
 
@@ -88,7 +88,7 @@ For the sake of simplicity, we are using admin keys in this example.
     ms bind ipv4 = true
     ms bind ipv6 = false
 
-    $ cat /var/snap/microceph/current/conf/ceph.keyring 
+    $ cat /var/snap/microceph/current/conf/ceph.keyring
     # Generated by MicroCeph, DO NOT EDIT.
     [client.admin]
         key = AQCNTXlmohDfDRAAe3epjquyZGrKATDhL8p3og==
@@ -100,24 +100,25 @@ Map the RBD image on client:
 
 .. code-block:: none
 
-    $ sudo rbd map bd_foo \
+    $ sudo rbd map \
+        --image bd_foo \
         --name client.admin \
         -m 192.168.29.152 \
         -k /var/snap/microceph/current/conf/ceph.keyring \
         -c /var/snap/microceph/current/conf/ceph.conf \
-        -p block_pool
-    /dev/rbd0
+        -p block_pool \
+        /dev/rbd0
 
     $ sudo mkfs.ext4 -m0 /dev/rbd0
     mke2fs 1.46.5 (30-Dec-2021)
-    Discarding device blocks: done                            
+    Discarding device blocks: done
     Creating filesystem with 2097152 4k blocks and 524288 inodes
     Filesystem UUID: 1deeef7b-ceaf-4882-a07a-07a28b5b2590
-    Superblock backups stored on blocks: 
+    Superblock backups stored on blocks:
         32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
 
-    Allocating group tables: done                            
-    Writing inode tables: done                            
+    Allocating group tables: done
+    Writing inode tables: done
     Creating journal (16384 blocks): done
     Writing superblocks and filesystem accounting information: done
 
@@ -155,12 +156,12 @@ Ceph cluster state post IO:
     cluster:
         id:     90457806-a798-47f2-aca1-a8a93739941a
         health: HEALTH_OK
-    
+
     services:
         mon: 1 daemons, quorum workbook (age 37m)
         mgr: workbook(active, since 51m)
         osd: 3 osds: 3 up (since 17m), 3 in (since 48m)
-    
+
     data:
         pools:   2 pools, 33 pgs
         objects: 24 objects, 23 MiB
@@ -169,4 +170,4 @@ Ceph cluster state post IO:
 
 Comparing the ceph status output before and after writing the file shows that
 the MicroCeph cluster has grown by 30MiB which is thrice the size of the file
-we wrote (10MiB). This is because MicroCeph configures 3 way replication by default.
+we wrote (10MiB). This is because MicroCeph configures 3 way replication by default.