I looked into this question among a few others (on and off SO) for a solution.
The upvoted (but not accepted) answer to that question, suggests entropy might be a problem.
I have infact from the beginning both haveng and rng-tools installed and enabled, and the entropy is pretty high (as per the comments on that answer, which suggest something close to 4000 as a good value).
$ cat /proc/sys/kernel/random/entropy_avail
$ 3703
I disabled a bunch of services, like Docker, lxc, etc that I thought might have been slowing down the boot process. Here is the critical-chain output after that. I don't think, there are any unnecessary services being started.
$ systemd-analyze critical-chain
The time when unit became active or started is printed after the "@" character.
The time the unit took to start is printed after the "+" character.
graphical.target @18.632s
└─multi-user.target @18.632s
└─ModemManager.service @12.750s +3.349s
└─polkit.service @9.288s +3.409s
└─basic.target @8.854s
└─sockets.target @8.854s
└─libvirtd-admin.socket @8.854s
└─libvirtd.socket @8.848s +5ms
└─sysinit.target @8.817s
└─systemd-sysctl.service @8.795s +21ms
└─systemd-modules-load.service @2.849s +5.941s
└─systemd-journald.socket @2.737s
└─-.mount @2.733s
└─system.slice @2.733s
└─-.slice @2.733s
Here is my lightdm.log.
[+7.13s] DEBUG: Process 1994 exited with return value 0
[+7.13s] DEBUG: Seat seat0: Exit status of /sbin/prime-offload: 0
[+7.13s] DEBUG: posix_spawn avoided (fd close requested) (child_setup specified)
[+7.13s] DEBUG: Seat seat0: Display server ready, starting session authentication
[+7.13s] DEBUG: Session pid=1999: Started with service 'lightdm-greeter', username 'lightdm'
[+7.40s] DEBUG: Session pid=1999: Authentication complete with return value 0: Success
[+7.40s] DEBUG: Seat seat0: Session authenticated, running command
[+7.40s] DEBUG: Session pid=1999: Running command /usr/lib/lightdm/lightdm-greeter-session /usr/sbin/lightdm-gtk-greeter
[+7.40s] DEBUG: Creating shared data directory /var/lib/lightdm-data/lightdm
[+7.40s] DEBUG: Session pid=1999: Logging to /var/log/lightdm/seat0-greeter.log
[+30.54s] DEBUG: Activating VT 7
[+30.54s] DEBUG: Activating login1 session c1
[+30.54s] DEBUG: Seat seat0 changes active session to c1
[+30.54s] DEBUG: Session c1 is already active
[+48.16s] DEBUG: Greeter connected version=1.30.0 api=1 resettable=false
[+49.90s] DEBUG: Greeter start authentication for junaid
[+49.90s] DEBUG: Session pid=6578: Started with service 'lightdm', username 'junaid'
[+49.92s] DEBUG: Session pid=6578: Got 1 message(s) from
I already tried switching to amdgpu-pro drivers from the amd website and that changed nothing. I reverted to the open source drivers.
I have also switched from lightdm to sddm and to gdm3 alternatively. Here is the output for that.
$ systemd-analyze
Startup finished in 7.564s (kernel) + 18.663s (userspace) = 26.228s
graphical.target reached after 18.632s in userspace
With lightdm, I just have a blank screen for ~30 seconds before the greeter appears.
$ systemd-analyze
Startup finished in 6.667s (kernel) + 16.169s (userspace) = 22.837s
graphical.target reached after 16.155s in userspace
Interesting thing about sddm is, the mouse cursor (although frozen) already appears almost immediately but the greeter does not appear for the next ~20 seconds.
$ systemd-analyze
Startup finished in 6.562s (kernel) + 52.061s (userspace) = 58.624s
graphical.target reached after 52.047s in userspace
$ systemd-analyze blame
41.779s plymouth-quit-wait.service
5.738s systemd-modules-load.service
5.519s udisks2.service
4.411s networkd-dispatcher.service
3.809s accounts-daemon.service
3.443s [email protected]
3.011s qemu-kvm.service
2.930s uml-utilities.service
2.614s dev-sdb5.device
2.459s ModemManager.service
2.205s polkit.service
2.158s avahi-daemon.service
2.136s NetworkManager.service
2.124s dundee.service
2.005s ofono.service
1.958s gpu-manager.service
1.920s grub-common.service
...
And finally Syslog shows that the kernel goes through with the bootup pretty fast (~4sec), till the following snags hit, taking up 20~30 seconds, which is about the time the screen remains blank&unresponsive before the login screen appears.
Dec 18 12:04:03 my-desktop NetworkManager[1057]: <info> [1639825443.5387] manager: NetworkManager state is now CONNECTED_GLOBAL
Dec 18 12:04:13 my-desktop systemd[1]: NetworkManager-dispatcher.service: Succeeded.
Dec 18 12:04:22 my-desktop systemd[1]: systemd-fsckd.service: Succeeded.
Dec 18 12:04:22 my-desktop systemd-timesyncd[996]: Initial synchronization to time server 91.189.89.199:123 (ntp.ubuntu.com).
Dec 18 12:04:26 my-desktop systemd[1]: systemd-hostnamed.service: Succeeded.
Dec 18 12:04:40 my-desktop systemd[1]: Created slice User Slice of UID 1000.
With gdm3, the boot-splash screen remains frozen for ~30 seconds before the login greeter appears.
I have a not so bad system put together a couple of years ago, with Ryzen 7 processor, 32GB RAM, 256GB SSD for the OS, and I am using an up to date Ubuntu 20.04 LTS.
So if there is a solution to this problem, it has eluded me in the last 2~3 hours.
