Merge pull request cncamp#3 from duydls/patch-1

Update 1.vm-install.md

Author: mfanjie

k8s-by-kubeadm/1.vm-install.md

@@ -2,6 +2,8 @@ If you are using Macbook, start from here:
 # download images and tools
 ##install virtualbox
 https://www.virtualbox.org/wiki/Downloads
+From System Preference -> Security & Privacy, allow Oracle access
+From Virtualbox -> File -> Host Network Manager, click Create button to create one
 
 ## install ubuntu iso from below link
 https://releases.ubuntu.com/20.04/
@@ -16,17 +18,17 @@ https://releases.ubuntu.com/20.04/
 
 ### boot new vm
 - click new button
-- choose OS as ubuntu 64bit and 30G disk
+- choose OS as ubuntu 64bit and 30G disk, make sure your #CPU>=2
 - start vm, choose the downloaded ubuntu ISO and follow the installation wizard
 - specify username/password like cadmin/cadmin
-- install ssh server
+- install ssh server, enable and start the service 
 - do not install built-in kubenernetes
 - wait enough long for the os installation complete
 
-### shutdown the OS, and set 2nd network adaptor
-- go vm->settings->network->adaptor 2
-- enable the adaptor and select host only adaptor, and choose vboxnet0, `vboxnet0` the host network name configured above
-### login to the system and set ip for second adaptor 
+### shutdown the OS, and set 2nd network adapter
+- go vm->settings->network->adapter 2
+- enable the adaptor and select host only adapter, and choose vboxnet0, `vboxnet0` the host network name configured above
+### login to the system and set ip for second adapter 
 ```
 vi /etc/netplan/00-installer-config.yaml
 
@@ -44,7 +46,7 @@ network:
 netplan apply
 ```
 ### network configuration
-now your vm has two adaptor:
+now your vm has two adapters:
 - one is nat which will get an IP automatically, generally it's 10.0.2.15, this interface is for external access from your vm
 - one is host adapter which need create extra ip, which is configured as 192.168.34.2
 the reason we need the host adaptor and static IP is then we can set this static IP as k8s advertise IP and you can move your VM in different everywhere.(otherwise your VM IP would be changed in different environment)
@@ -56,4 +58,4 @@ the reason we need the host adaptor and static IP is then we can set this static
 swapoff -a
 vi /etc/fstab
 remove the line with swap keyword
-```
+```