Ubuntu – How to know what a snap will install

debsnap

OS: Ubuntu 18.04

When I search the software center for kmag, I get two results: one for a .deb and one for a snap.

The .deb mentions a download size of 627.5 kB:

The snap download appears to be smaller, at 237.6 kB:

In the case of the .deb, because I have some knowledge, I can open a terminal and run sudo apt install kmag to find out that 6,744 kB of archives will actually be required taking up 36.4 MB of additional disk space.

How would a user, especially a relative newcomer, know beforehand what the snap installation will entail in terms of how much will be downloaded and how much additional disk space will be used?

I went through the process of installing the kmag snap on Ubuntu 19.04.

The following image shows the folder size of kde-frameworks-5-core18 is 865.6 MB whereas the folder size for kmag is only 679 kB. The information provided by the software center or by running snap info kmag doesn't give the user any clue that kde-frameworks-5-core18 will be installed (with a size of 865.6 MB).

Best Answer

Get size information:
snap info kmag

Get more information about the snap format:
https://docs.snapcraft.io/snap-format

In short
A snap is a Squashfs file located in /var/lib/snapd/snaps/ mounted to /snap/

Related Solutions

Snap Packaging Format – What is It?

Why did Canonical chose snaps?

To quote the Ubuntu website:

We originally created the snappy technology and application confinement system to ensure a carrier-grade update experience for Ubuntu mobile users and set a new standard for application security in the mobile era.

Essential idea was to fix issues that are present in both .deb packages and provide new method for updating the packages (the so called transactional updates , very similar to how android apps are updated). As Mark Shuttleworth explains:

Whenever we make a fix to packages in Ubuntu, we’ll publish the same fix to Ubuntu Core, and systems can get that fix transactionally. In fact, updates to Ubuntu Core are even smaller than package updates because we only need to send the precise difference between the old and new versions, not the whole package.

What are the main advantages of .snap packages over .deb packages?

The biggest advantage is the improved security. PPAs and .deb packages are typically installed with root privillege , which opens up a venue for security risks.

Snappy apps are isolated, meaning that if some app breaks, it won't break your systems. To quote Mark Shuttleworth:

Snappy packages are automatically confined to ensure that a bug in one app doesn’t put your data elsewhere at risk

Will .deb be abandoned?

As of Ubuntu 16.04 LTS , both methods are available to the users.

To quote OMG! Ubuntu!:

Canonical also say that “…the tens of thousands of applications and packages in .deb format will continue to be supported in 16.04 and beyond, and deb archives in particular will continue to be available for all to use and distribute software.”

Package Management – How to Install .snap Application on an Offline Computer

First of all, you can indeed install debs offline:

$ sudo dpkg -i <deb>

However, you're right in that it doesn't take into account the deb's dependencies-- you actually need to have the deb and all its dependencies available offline in order to successfully install it:

$ sudo dpkg -i <deb> <dependency1> <dependency2> ...

So yes, installing a snap offline is very easy, and all you need to have is that single snap (since as you know, it includes its dependencies):

$ sudo snap install path/to/snap

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