Snapd.service delays startup in Ubuntu 18.04 with 4.15.0-24


#10

Sorry to hear that this is causing problems for you. We are currently looking into fixing the problem. As a workaround you can press the “shift” key and move the mouse during bootup this will make the login quicker. Regarding the testing - I can assure you that we test snapd very carefully, we run thousands of tests each time we change snapd. However when something external like the kernel changes behaviour we can’t do anything to foresee that. We are working on a fix now that we know what is going on.
[edit: spelling]


#11

There are recovery options on boot, you could select to boot the previous kernel which, to the best of our understanding, boot the system normally. In addition you can reinstall a system without wiping your data which would save you the trouble. In any case we are sorry for the issues you experienced. Snapd cannot block updates of the distribution kernel so this is something that was difficult to avoid.

As a matter of testing we test every single change we make on about 50 virtual machines running a variety of operating systems. Nothing is perfect but we take this very seriously.


#12

Hi! This is my output for the commands.

apt list snapd -a
Listing... Done
snapd/bionic-updates,now 2.32.9+18.04 amd64 [installed]
snapd/bionic 2.32.5+18.04 amd64

snap version
snap    2.33.1
snapd   2.33.1
series  16
ubuntu  18.04
kernel  4.15.0-24-generic

systemd-detect-virt
none

uname -r
4.15.0-24-generic

#13

While this looks like a bug in the kernel it is probably still worth to investigate why we need data from getrandom() at bootup.

Looking at our code it looks like we have two places:

  • catalogUpdate talks to the store at startup and that uses randomness
  • importing “gopkg.in/mgo.v2/bson” which triggers the initialization of var objectIdCounter uint32 = readRandomUint32() which reads 4 bytes of randomness from randr.Reader

The catalogUpdate runs in a goroutine (thanks Samuele for pointing this out) so that is not blocking the READY=1 notification for systemd.

However we also import mgo.v2/bson/ which initializes a variable using (objectIdCounter = readRandomUint32()) which reads rand.Reader. This happens before snapd main() and blocks with the new kernel. Replacing this with a time.Now().Unix() based value makes the problem go away (but I don’t know enough about bson to know if that is correct).

[edit: updated based on feedback from Sameuele]


#14
patrick@patrick-desk:~$ apt list snapd
Listing... Done
snapd/bionic-updates,now 2.32.9+18.04 amd64 [installed]
N: There is 1 additional version. Please use the '-a' switch to see it
patrick@patrick-desk:~$ snap version
snap    2.33.1
snapd   2.33.1
series  16
ubuntu  18.04
kernel  4.15.0-24-generic
patrick@patrick-desk:~$ systemd-detect-virt 
none
patrick@patrick-desk:~$ uname -r
4.15.0-24-generic

#15

This https://github.com/snapcore/snapd/pull/5464 will hopefully fix the issue for most people. Please note that its still not clear if this is not a kernel issue (I would argue it is) but even if it is the above fix should unblock people (will still need review/merge/SRU).


#16

And it looks like the kernel team has reverted the problematic update and is working on a fix now.


#17

Please, tell, how to use this fix. Can’t handle it :frowning:


#18

As a workaround you can press keys/move the mouse at bootup. The real fix is either a kernel upgrade or downgrade. But we will try to push a snapd update out that also will partially fix the issue.


#19

Thanks! Looking forward to seeing superfast ubuntu booting again


#20

A new snapd 2.33.1+18.04ubuntu2 has just hit the archive. Please try to upgrade to this version and that hopefully fixes the slow boot. The usual apt update && apt install snapd should work. It may take a bit until the package is available on all mirrors though.


#21

just for completeness, this is

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1780062


#22

I’ve got the same issue.
systemd-analyze blame shows 1min 24.186s snapd.service

Thanks mvo for the temporary fix. I just booted to grub, selected an old kernel, and sure enough, fast boot time!
Fast settings below:

jayshomebrew@ubuntu:~$ apt list snapd
Listing... Done
snapd/bionic-updates,now 2.32.9+18.04 amd64 [installed]
N: There is 1 additional version. Please use the '-a' switch to see it
jayshomebrew@ubuntu:~$ 
jayshomebrew@ubuntu:~$ systemd-detect-virt 
none
jayshomebrew@ubuntu:~$ uname -r
4.15.0-23-generic
jayshomebrew@ubuntu:~$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 18.04 LTS
Release:	18.04
Codename:	bionic
jayshomebrew@ubuntu:~$ snap version
snap    2.33.1
snapd   2.33.1
series  16
ubuntu  18.04
kernel  4.15.0-23-generic


#23

Still seem to be getting the same issue.

tim@TimGJ:~$ sudo systemd-analyze blame
1min 49.280s snapd.seeded.service
     18.778s snapd.service
      7.026s NetworkManager-wait-online.service
      1.212s mariadb.service
       762ms fwupd.service
       747ms dev-sda1.device
       503ms dev-loop0.device
       493ms dev-loop3.device
       490ms dev-loop1.device
       487ms dev-loop2.device
       471ms dev-loop4.device
       468ms dev-loop7.device
       459ms dev-loop5.device
       459ms dev-loop6.device
       442ms dev-loop8.device
       431ms dev-loop9.device
       430ms dev-loop11.device
       430ms dev-loop10.device
       425ms dev-loop12.device
       418ms dev-loop14.device
       417ms dev-loop13.device
       401ms dev-loop15.device
       397ms dev-loop16.device
tim@TimGJ:~$ apt list snapd
Listing... Done
snapd/bionic-updates,now 2.32.9+18.04 amd64 [installed]
N: There is 1 additional version. Please use the '-a' switch to see it
tim@TimGJ:~$ snap version
snap    2.33.1
snapd   2.33.1
series  16
ubuntu  18.04
kernel  4.15.0-24-generic
tim@TimGJ:~$ systemd-detect-virt 
none

#24

My father reported this issue on Friday, and three of my test systems fell ill on Monday & Tuesday. I can confirm 2.33.1+18.04ubuntu2 is not working, nor is the old 2.32.5.

I was only able to solve this problem by either configuring grub to boot revision 23 of the kernel, or by subscribing to the preview channel and upgrading to kernel 4.15.0.26

Hardware seems to play a role. I was able to boot my father’s Ubuntu on my coffeelake system without problem or delay. Coffeelake, skylake and apollo lake are all immune, while braswell and haswell are affected.

I am not sure this is a fault of snapd or something peculiar to revision 24 of the kernel


#25

In my case, Alt+F2 brings me to the login screen.


#26

Try Alt+F2 when it’s stuck on loading.


#27

I reinstalled about a week ago before there was more debugging information available. Then the same thing happened to my wife’s laptop last night. Blocking on reading the random device reminded me of another problem that I had on startup of Ubiquity’s Unifi controller.

Installing haveged:

apt-get install haveged

Made my wife’s laptop boot very quickly. I believe that the problem is the random pool doesn’t have enough entropy at boot and the software reads from from random, not urandom which stirs the pool.


#28

Using the shift key works. It didn’t hold the boot and join in X.

➜  ~ apt list snapd   
snapd/bionic-updates,now 2.32.9+18.04 amd64 [installed]
➜  ~ snap version
snap    2.33.1
snapd   2.33.1
series  16
ubuntu  18.04
kernel  4.15.0-24-generic
➜  ~ systemd-detect-virt 
none
➜  ~ uname -r
4.15.0-24-generic

#29

I’m having the same problem as reported here.

apt list snapd -a
snapd/bionic-updates,now 2.34.2+18.04 amd64 [instal·lat]
snapd/bionic 2.32.5+18.04 amd64

snap version
snap 2.35.2
snapd 2.35.2
series 16
ubuntu 18.04
kernel 4.15.0-36-generic

systemd-detect-virt
none

uname -r
4.15.0-36-generic

I experience this issue not always. Normally, when this problem appears, I shut down the computer and start it again. Then the process goes fine. Any idea about? Thanks in advance.