Cfrgtkky

As of Ubuntu 18.04 running lsblk shows 16 snap loops (2-3 times for each snap). The question is, why are they being listed as results for lsblk, fdisf-l, and blkid?

It creates a lot of clutter from the actual disks drive partitions I need to see, namely /dev/ partitions. I know a purported duplicate of this question exists, but it only asks why three loops are being listed per snap. I want to know why these snaps are being listed in the first place, and the purported duplicate does not answer this (perhaps those marking this as duplicate could help me by explaining why it is a duplicate). Technically, they qualify as file systems (which I neither created nor asked for), but they are getting in the way of the information output for the /dev/ partitions I am interested in. This becomes a problem when fdisk -l outputs a three page+ list filled mainly with snaps.

The output of a recent (1 week old) Ubuntu install and I have not installed any snaps:

$ lsblk  

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT  

loop0    7:0    0  14.5M  1 loop /snap/gnome-logs/37  

loop1    7:1    0   2.3M  1 loop /snap/gnome-calculator/170  

loop2    7:2    0  86.6M  1 loop /snap/core/4486  

loop3    7:3    0  86.6M  1 loop /snap/core/4650  

loop4    7:4    0   1.6M  1 loop /snap/gnome-calculator/154  

loop5    7:5    0  14.5M  1 loop /snap/gnome-logs/34  

loop6    7:6    0   3.3M  1 loop /snap/gnome-system-monitor/36  

loop7    7:7    0   2.3M  1 loop /snap/gnome-calculator/178  

loop8    7:8    0    13M  1 loop /snap/gnome-characters/101  

loop9    7:9    0   3.7M  1 loop /snap/gnome-system-monitor/45  

loop10   7:10   0 139.5M  1 loop /snap/gnome-3-26-1604/64  

loop11   7:11   0   140M  1 loop /snap/gnome-3-26-1604/59   

loop12   7:12   0   3.7M  1 loop /snap/gnome-system-monitor/41  

loop13   7:13   0    21M  1 loop /snap/gnome-logs/25  

loop14   7:14   0  12.2M  1 loop /snap/gnome-characters/69  

loop15   7:15   0    13M  1 loop /snap/gnome-characters/96  

sda      8:0    0 298.1G  0 disk  

├─sda1   8:1    0   512M  0 part /boot/efi  

└─sda2   8:2    0 297.6G  0 part /  

sr0     11:0    1  1024M  0 rom  

(supplemental screen capture of above text):
screenshot.jpg

My snap list shows 6 results:

core

gnome-3-26-1604

gnome-calculator

gnome-characters

gnome-logs

gnome-system-monitor

Meanwhile, gnome-disk-utility shows nothing at all for snaps, only showing my HDD and optical drive.

It won't be very efficient if every installed snap gets listed as a block device (2-3 times each to add). Should I expect future updates to deal with this?

Edit:
fdisk-l also dumps out a very long list with 16 instances of these "disk loops" (Disk /dev/loop0, Disk /dev/loop1, etc., each with details which I won't show here because it's too long). This can't be intended behaviour, can it?
blkid also lists 16 loops, as TYPE="squashfs". At least parted -l works as expected, only outing my actual disk partitions.

I just tested this, and installing more snaps does add more to the lsblk output. Therefore, fdisk, lsblk, blkid could have potentially huge output lists, according to the number of snaps available, and installed.

When you type the command

snap list 

you will get the output of actual installed snap packages. The reason is when a snap package is updated, the old version is kept (see snapcraft docu).

Citate from snapcraft docu

Garbage collection then removes and purges any snap files, and their writable areas, for snap versions prior to the one that has just been updated — meaning that, at most, two versions of a snap will be present on the system. This saves disk space without compromising the ability to revert the snap to a previous known-good state.

Explicitly removing a snap from your system will also remove the code and purge the data for all prior versions.

For instance you have got installed more than one versions of gnome-calculator.

In case you only need the newest version, you can use

sudo snap remove gnome-calculator --revision <verison to be placed>

Using the command

losetup -a 

shows you the mounted snaps (loop devices)

If you want to delete the double ones, type

sudo losetup -d /dev/loop<loopnumber>

It seems to be an error of the snap code, since all older been kept in the /var/lib/snapd/snaps file.

From the content in your question, your problem is about searching for a way to have control over what you're seeing when you try to view your block devices than how snap uses block devices for its operation.

I agree with your referenced distinction between fdisk -l and parted -l. While fdisk shows a very good detailed output of block devices, it shows too many other things that distract from what you're trying to see.

Resolution

You can use filter the lsblk formatted output. This works well to give a clean output like what you get with gnome-disk-utility.

$ lsblk -o name,mountpoint,label,size,fstype,uuid | egrep -v "^loop"

Or as you indicated in your question:

$ sudo parted -l

For the df command in your question, use:

$ df | egrep -v /dev/loop

If you use the snap version of the system monitor, then you will see all file systems used by snap as well as the ones you use.

An easy "fix" is to uninstall Gnome System Monitor from the app store. It is the snap-version.

Then install Gnome System Monitor from the normal repositories using Synaptic package manager. It is the normal version that installs a bunch of files all over you root partition. Nice!

And you will see just what you expect to see when you launch Gnome System Monitor...

I find this annoying too. It seems if they are not running they should not be mounted or listed.
You can run this command to exclude all the loop devices.

$ lsblk -e 7

To only show mounts excluding loopback you could also simply:

lsblk -af |grep -sv loop

;)