How to install unzip on a Synology NAS

Under DSM, Synology preferred to install the 7zip compacting tool (which is very good) instead of zip and unzip.
But many software installation scripts require unzip to install or operate.
It is therefore useful to install this tool in addition to 7zip.

But for that, you will first have to install the Entware opkg package manager (which replaces the aging ipkg).

Here is the whole procedure to follow:

• First, install Entware following the procedure described on this page.
• Then just type the command
  

  sudo opkg install unzip​

  At the end of this command, unzip is installed in the directory /volume1/@ entware-ng/opt/bin.
  If all the steps of the package manager installation procedure have been followed, then unzip is accessible via the PATH variable.

• However, in the event that a script testing the existence of unzip under /bin is executed, it is always possible to execute the symbolic link command beforehand
  

  ln -s /volume1/@entware-ng/opt/bin/unzip /bin/unzip​

  which will make unzip accessible via this directory.