the software of synaptic install failed

hello,

sudo apt-get update

Hit:1 http://ports.ubuntu.com/ubuntu-ports xenial InRelease
Hit:2 http://ports.ubuntu.com/ubuntu-ports xenial-updates InRelease
Hit:3 http://ports.ubuntu.com/ubuntu-ports xenial-security InRelease
Reading package lists… Done

sudo apt-get install synaptic

Reading package lists… Done
Building dependency tree
Reading state information… Done
Package synaptic is not aailable, but is refered to by another package.
This may mean that the package is missing,has been obsoketed,or is only available from another source
E: Package ‘synaptic’ has no installation candidate

How to install synaptic?
Thank you very much.

This installs for me on R28.2 (I have all repositories enabled…perhaps the dependency is for a package in a repository you don’t have enabled).

A reverse dependency check:

# apt-cache rdepends --installed synaptic
synaptic
Reverse Depends:
  update-notifier                                                                                   
 |apt                                                                                               
  update-notifier                                                                                   
  update-manager                                                                                    
 |apt                                                                                               
  update-notifier                                                                                   
 |apt                                                                                               
  update-manager

What do you get if you run:

sudo apt-get install update-notifier update-manager

If you see packages installed but no longer required, perhaps one is in the way…run:

sudo apt autoremove

…then try install again.