Questions[loop-device](ubuntu)

On my Ubuntu desktop, the command fdisk -l shows /dev/loopX up to /dev/loop23. I'm using gnome-fallback on Ubuntu 18.04 LTS.

I'm wondering what possible effects these could have on performance and stabilty of the OS, and if they are just superfluous, how can I remove them?

root@pc5:~# fdisk -l
...
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop15: 3.7 MiB, 3821568 bytes, 7464 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop16: 54.6 MiB, 57274368 bytes, 111864 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop17: 140.7 MiB, 147501056 bytes, 288088 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop18: 14.8 MiB, 15462400 bytes, 30200 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop19: 42.8 MiB, 44879872 bytes, 87656 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop20: 54.5 MiB, 57151488 bytes, 111624 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop21: 4.2 MiB, 4403200 bytes, 8600 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop22: 153.5 MiB, 160935936 bytes, 314328 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/loop23: 140.7 MiB, 147501056 bytes, 288088 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

output of df:

Filesystem      1K-blocks       Used  Available Use% Mounted on
udev              8128184          0    8128184   0% /dev
tmpfs             1630464       3716    1626748   1% /run
/dev/sda2       229184876   63255488  154217748  30% /
tmpfs             8152300     142672    8009628   2% /dev/shm
tmpfs                5120          4       5116   1% /run/lock
tmpfs             8152300          0    8152300   0% /sys/fs/cgroup
/dev/loop2         160512     160512          0 100% /snap/gnome-3-28-1804/110
/dev/loop3           4352       4352          0 100% /snap/gnome-calculator/544
/dev/loop0           3840       3840          0 100% /snap/gnome-system-monitor/111
/dev/loop4          91264      91264          0 100% /snap/core/8039
/dev/loop1           1024       1024          0 100% /snap/gnome-logs/81
/dev/loop6          87936      87936          0 100% /snap/shotcut/55
/dev/loop5         406528     406528          0 100% /snap/redis-desktop-manager/332
/dev/loop8          91264      91264          0 100% /snap/core/8213
/dev/loop7         406656     406656          0 100% /snap/redis-desktop-manager/335
/dev/loop9          15104      15104          0 100% /snap/gnome-characters/367
/dev/loop11        157184     157184          0 100% /snap/chromium/949
/dev/loop12         87808      87808          0 100% /snap/shotcut/53
/dev/loop13          1024       1024          0 100% /snap/gnome-logs/73
/dev/loop14         45312      45312          0 100% /snap/gtk-common-themes/1353
/dev/loop16         55936      55936          0 100% /snap/core18/1279
/dev/loop15          3840       3840          0 100% /snap/gnome-system-monitor/107
/dev/loop10        159872     159872          0 100% /snap/gnome-3-28-1804/91
/dev/loop17        144128     144128          0 100% /snap/gnome-3-26-1604/97
/dev/sda1          523248       6232     517016   2% /boot/efi
/dev/loop18         15104      15104          0 100% /snap/gnome-characters/359
/dev/loop19         43904      43904          0 100% /snap/gtk-common-themes/1313
/dev/loop20         55936      55936          0 100% /snap/core18/1265
/dev/loop21          4352       4352          0 100% /snap/gnome-calculator/536
/dev/loop22        157184     157184          0 100% /snap/chromium/958
/dev/loop23        144128     144128          0 100% /snap/gnome-3-26-1604/98
/dev/sdb1       492127240  409174612   57930932  88% /home
tmpfs             1630460         16    1630444   1% /run/user/121
tmpfs             1630460        140    1630320   1% /run/user/1001
tmpfs             1630460          0    1630460   0% /run/user/0

I am trying to setup Bochs as shown in this tutorial. However, I'm using WSL and there is no loop0 device.

# bochsrc.txt #
megs:        32
romimage:    file=/usr/share/bochs/BIOS-bochs-latest, address=0xf0000
vgaromimage: /usr/share/bochs/VGABIOS-elpin-2.40
floppya:     1_44=/dev/loop0, status=inserted
boot:        a
log:         bochsout.txt
mouse:       enabled=0
clock:       sync=realtime
cpu:         ips=500000

# update_image.sh #    
sudo losetup /dev/loop0 floppy.img
sudo mount   /dev/loop0 /mnt
sudo cp      src/kernel /mnt/kernel
sudo umount  /dev/loop0
sudo losetup -d /dev/loop0 

# run_bochs.sh #
# mounts the correct loopback device, runs bochs, then unmounts
sudo losetup /dev/loop0 floppy.img
sudo bochs   -f bochsrc.txt
sudo losetup -d /dev/loop0

Available devices are:

• block
• fd
• kmsg
• lxss
• null
• ptmx
• pts
• stdin
• stdout
• stderr
• shm
• tty[x]
• zero

Is there any way I can tweak the above code to work with an available device?

I used lsblk to check connected devices, when I found that there are a total of 3 loop devices for the same snap "core", with revision numbers.

loop1    7:1    0  81.6M  1 loop /snap/core/4110
loop2    7:2    0  81.7M  1 loop /snap/core/4017
loop0    7:0    0  81.3M  1 loop /snap/core/3887

On checking the mount directory of snaps, this is what I get:

drwxr-xr-x 24 root root 321 Jan 22 13:17 3887
drwxr-xr-x 24 root root 321 Feb  6 20:48 4017
drwxr-xr-x 24 root root 321 Feb 20 22:37 4110
lrwxrwxrwx  1 root root   4 Feb 23 19:31 current -> 4110

and snap list shows this:

core  16-2.31.1  4110  canonical  core

Why is snapd not removing the old versions of snap core? Is it a normal behavior, or is there any way to remove this if this is not supposed to happen? I'm using Ubuntu 16.04.

A lot of strange loop devices appear in my Kubuntu OS.

 [translation:  
  Hard disk 107.4GB  
  Hard disk 487.0GB  
  Loop Device  
  Hard Disk 4.0GB  
  Loop Device  
  Loop Device  
  Loop Device  
  Loop Device  
  Victor Disk]

Can anybody tell me what it is? .

$ df -kh
Filesystem      Size  Used Avail Use% Mounted on
udev            7,8G     0  7,8G   0% /dev
tmpfs           1,6G   19M  1,6G   2% /run
/dev/sda2       622G  227G  364G  39% /
tmpfs           7,8G  1,1G  6,7G  14% /dev/shm
tmpfs           5,0M  4,0K  5,0M   1% /run/lock
tmpfs           7,8G     0  7,8G   0% /sys/fs/cgroup
/dev/loop1      143M  143M     0 100% /snap/inkscape/2527
/dev/loop3       79M   79M     0 100% /snap/core/1441
/dev/loop0       79M   79M     0 100% /snap/core/1577
/dev/loop4       79M   79M     0 100% /snap/core/1512
/dev/loop2       62M   62M     0 100% /snap/pencilsheep/5
tmpfs           1,6G   92K  1,6G   1% /run/user/1000

What are these /dev/loop device files? My RAM is always full. Is this related?