Follow the guidelines for How To Expand The YUN DISK SPACE https://www.arduino.cc/en/Tutorial/ExpandingYunDiskSpace
For the reboot, you need to press the YUN RST button. and then, you will see the context msg in the serial monitor.
You can press Enter twice or I would recommend you to install PUTTY(Optional) for serial communication and follow the guidelines below after your message in serial monitor:-
Close Serial Monitor.
Open Putty and do the steps below.
As you can see we have 2.5 GB of free disk space.
As per the link Expanding YUN disk space, you can see the partition at the bottom of the page:-
df -h //mnt/sda1
The output should look like this:
Filesystem Size Used Available Use% Mounted on
rootfs 1.2G 51.7M 1.0G 5%/ // This is the overlay partition and your files will be stored under this partitioned memory.
/dev/sda1 698.6M 12.0K 698.6M 0%/mnt/sda1
Try installing one package after the opkg update for instance (opkg install python-pip or opkg install vim)
Go to the cd /usr/bin and type ls. You can see the list of installed packages over there plus python-pip and vim also.
Close the serial communication and remove the SD card, and, open the serial communication again and try searching the packages in cd /usr/bin by ls.
You won't see it as these packages are installed in the overlay partition i.e the memory card partitioned by Yun disk space expander.