从 16 LTS 升级后，我在 ubuntu 18 中遇到了启动时间问题。以下是systemd-analyze blame
1min 9.470s plymouth-start.service
1min 8.107s plymouth-read-write.service
48.640s plymouth-quit-wait.service
45.970s apt-daily.service
16.562s dev-sda8.device
13.815s systemd-journal-flush.service
13.615s keyboard-setup.service
13.369s systemd-tmpfiles-setup-dev.service
12.658s systemd-sysctl.service
9.577s NetworkManager-wait-online.service
4.732s mysql.service
3.813s NetworkManager.service
3.429s udisks2.service
3.242s networkd-dispatcher.service
2.815s apparmor.service
2.640s snapd.service
2.493s ModemManager.service
2.329s accounts-daemon.service
2.125s grub-common.service
1.966s systemd-random-seed.service
1.734s dev-loop8.device
1.656s gpu-manager.service
1.524s thermald.service
1.489s dev-loop9.device
1.443s dev-loop10.device
1.323s dev-loop2.device
1.323s dev-loop1.device
1.322s dev-loop0.device
1.319s dev-loop4.device
1.314s dev-loop5.device
1.313s dev-loop7.device
1.312s dev-loop6.device
1.305s dev-loop3.device
1.037s systemd-remount-fs.service
1.032s fwupd.service
982ms sys-kernel-debug.mount
有人知道如何减少它吗？或者如果我的系统有问题，如何修复？
谢谢。