我在用着Ubuntu 20.04 LTS. 开机时间为增加急剧下降。我该如何减少启动时间？哪些服务可以停止？
以下是输出systemd-analyze blame：
2min 1.371s connman-wait-online.service
1min 29.696s nmbd.service
39.727s mysql.service
34.196s udisks2.service
30.499s man-db.service
30.076s systemd-journal-flush.service
28.287s [email protected]
25.887s plymouth-quit-wait.service
23.571s networkd-dispatcher.service
23.567s snapd.service
22.759s logrotate.service
20.528s NetworkManager-wait-online.service
19.988s [email protected]
19.236s dev-sda5.device
13.308s accounts-daemon.service
12.483s apache2.service
11.346s polkit.service
10.809s dev-loop21.device
10.805s avahi-daemon.service
10.802s bluetooth.service
10.792s NetworkManager.service
10.779s connman.service
10.769s dundee.service
10.762s ofono.service
10.731s dev-loop11.device
10.664s dev-loop23.device
10.611s dev-loop18.device
10.510s dev-loop17.device
10.501s dev-loop28.device
10.415s switcheroo-control.service
10.410s thermald.service
10.394s wpa_supplicant.service
10.386s systemd-logind.service
10.371s dev-loop27.device
10.217s dev-loop19.device
10.139s vboxdrv.service
9.931s dev-loop25.device
9.865s dev-loop26.device
9.703s dev-loop8.device
9.581s dev-loop20.device
9.229s dev-loop22.device
9.060s dev-loop16.device
8.922s dev-loop9.device
8.919s dev-loop15.device
8.888s dev-loop24.device
8.305s dev-loop10.device
8.210s dev-loop7.device
8.014s ModemManager.service
7.848s dev-loop12.device
7.073s dev-loop0.device
6.946s dev-loop3.device
6.837s dev-loop1.device
6.834s dev-loop14.device
6.497s redis-server.service
6.457s dev-loop5.device
6.321s dev-loop2.device
6.296s systemd-resolved.service
6.218s dev-loop13.device
6.124s gpu-manager.service
6.052s dev-loop6.device
5.453s dev-loop4.device
4.993s fwupd.service
4.530s rsyslog.service
3.600s apt-daily-upgrade.service
3.543s grub-common.service
3.462s apport.service
3.450s systemd-fsck@dev-disk-by\x2duuid-18B7\x2d5624.service
3.000s plymouth-read-write.service
2.986s e2scrub_reap.service
2.882s grub-initrd-fallback.service
2.421s systemd-udevd.service
2.234s snap-canonical\x2dlivepatch-95.mount
2.120s snap-chromium-1373.mount
2.032s snap-chromium-1382.mount
2.023s snap-core-10126.mount
2.004s snap-core-10185.mount
1.914s ssh.service
1.895s apparmor.service
1.769s snap-core18-1885.mount
1.656s snap-core18-1932.mount
1.627s snapd.seeded.service
1.611s snap-gnome\x2d3\x2d26\x2d1604-100.mount
1.610s snap-gnome\x2d3\x2d26\x2d1604-98.mount
1.492s snap-gnome\x2d3\x2d28\x2d1804-128.mount
1.488s networking.service
1.448s snap-gnome\x2d3\x2d28\x2d1804-145.mount
1.409s snap-gnome\x2d3\x2d34\x2d1804-36.mount
1.320s snap-gnome\x2d3\x2d34\x2d1804-60.mount
1.298s snap-gnome\x2dsystem\x2dmonitor-145.mount
1.297s snap-gnome\x2dsystem\x2dmonitor-148.mount
1.267s snapd.apparmor.service
1.219s systemd-tmpfiles-setup.service
1.198s snap-gtk\x2dcommon\x2dthemes-1502.mount
1.196s snap-gtk\x2dcommon\x2dthemes-1506.mount
1.091s snap-heroku-3997.mount
1.090s snap-heroku-3999.mount
1.010s sysstat.service
1.008s xl2tpd.service
978ms systemd-sysusers.service
970ms systemd-modules-load.service
899ms systemd-random-seed.service
897ms smbd.service
830ms gdm.service
730ms snap-insomnia-105.mount
703ms tlp.service
673ms [email protected]
649ms snap-insomnia-109.mount
594ms systemd-backlight@leds:asus::kbd_backlight.service
588ms snap-qt551-30.mount
584ms systemd-udev-trigger.service
534ms systemd-journald.service
490ms snap-pycharm\x2dcommunity-214.mount
483ms upower.service
476ms keyboard-setup.service
465ms snap-pycharm\x2dcommunity-211.mount
463ms plymouth-start.service
463ms systemd-backlight@backlight:intel_backlight.service
440ms systemd-sysctl.service
421ms swapfile.swap
417ms [email protected]
405ms dns-clean.service
384ms systemd-tmpfiles-setup-dev.service
358ms snap-vlc-1620.mount
341ms pppd-dns.service
339ms binfmt-support.service
331ms snap-scrcpy-254.mount
324ms snap-scrcpy-243.mount
296ms snap-qt551-29.mount
253ms ifupdown-pre.service
250ms snap-vlc-1700.mount
234ms systemd-timesyncd.service
224ms alsa-restore.service
205ms rtkit-daemon.service
203ms colord.service
198ms apport-autoreport.service
195ms openvpn.service
189ms [email protected]
170ms console-setup.service
144ms systemd-remount-fs.service
144ms tor.service
131ms kerneloops.service
127ms blueman-mechanism.service
126ms ufw.service
116ms kmod-static-nodes.service
116ms systemd-update-utmp.service
109ms boot-efi.mount
87ms vboxballoonctrl-service.service
86ms vboxautostart-service.service
59ms setvtrgb.service
59ms systemd-user-sessions.service
56ms dev-hugepages.mount
55ms dev-mqueue.mount
54ms sys-kernel-debug.mount
54ms sys-kernel-tracing.mount
41ms vboxweb-service.service
39ms [email protected]
37ms proc-sys-fs-binfmt_misc.mount
28ms packagekit.service
18ms systemd-tmpfiles-clean.service
16ms systemd-update-utmp-runlevel.service
3ms sys-fs-fuse-connections.mount
2ms sys-kernel-config.mount
1ms postgresql.service
759us snapd.socket
更新： 删除 snap 并禁用不需要的服务后，这是更新后的输出：
1min 18.932s apport-autoreport.service
18.404s udisks2.service
13.156s networkd-dispatcher.service
10.534s accounts-daemon.service
9.833s [email protected]
7.489s polkit.service
7.049s switcheroo-control.service
6.946s avahi-daemon.service
6.939s NetworkManager.service
6.929s connman.service
6.917s dundee.service
6.869s ofono.service
6.774s ModemManager.service
6.652s thermald.service
6.652s systemd-logind.service
6.630s wpa_supplicant.service
6.538s dev-sda5.device
6.221s vboxdrv.service
4.375s grub-initrd-fallback.service
4.188s gpu-manager.service
3.881s ssh.service
3.861s grub-common.service
3.456s xl2tpd.service