我在使用 Ubuntu 时遇到了启动速度非常慢的问题，
$ systemd-analyze time
Startup finished in 9.143s (kernel) + 2min 4.895s (userspace) = 2min 14.038s
graphical.target reached after 2min 4.885s in userspace
这太长了，我使用的也不是史前机器，处理器是英特尔 i5-4200M，还可以，应该花不了 2 分钟。
另外，自从我第一次在这台机器上安装 Ubuntu（大约一年前）以来，我就遇到了这个问题，之前我已经重新安装了 Ubuntu 很多次，但问题仍然存在。
$ systemd-analyze plot > init1.svg
给我（Imgur 不支持 svg，所以必须与链接有关）：https://svgshare.com/i/Vx5.svg
这里有一些额外的信息；
$ systemd-analyze blame
1min 20.804s vboxdrv.service
39.768s snapd.service
33.076s dev-sda6.device
21.262s networkd-dispatcher.service
16.373s udisks2.service
12.864s NetworkManager.service
12.204s NetworkManager-wait-online.service
11.933s accounts-daemon.service
11.776s apache2.service
11.567s dev-loop45.device
11.422s dev-loop48.device
11.399s dev-loop46.device
11.332s dev-loop44.device
11.246s dev-loop47.device
11.148s dev-loop30.device
11.116s ufw.service
10.892s dev-loop35.device
10.771s loadcpufreq.service
10.661s dev-loop43.device
10.430s dev-loop42.device
10.327s dev-loop39.device
10.234s systemd-journal-flush.service
10.219s dev-loop41.device
10.110s dev-loop40.device
9.967s dev-loop37.device
9.944s dev-loop38.device
9.705s ModemManager.service
9.640s dev-loop36.device
9.466s dev-loop34.device
9.274s dev-loop33.device
9.041s thermald.service
8.999s dev-loop32.device
8.961s teamviewerd.service
8.926s dev-loop25.device
8.893s dev-loop27.device
8.864s dev-loop31.device
8.803s snap-anbox-186.mount
8.746s snap-authy-5.mount
8.731s dev-loop23.device
8.644s snap-cheat-2681.mount
8.633s snap-cheat-2698.mount
8.615s snap-cmake-834.mount
8.594s snap-cmake-846.mount
8.588s dev-loop29.device
8.545s wpa_supplicant.service
8.487s snap-code-60.mount
8.467s dev-loop28.device
8.209s dev-loop26.device
8.045s dev-loop24.device
7.903s polkit.service
7.815s dev-loop22.device
7.794s dev-loop21.device
7.763s dev-loop19.device
7.494s dev-loop9.device
7.255s dev-loop8.device
7.112s avahi-daemon.service
7.084s dev-loop20.device
7.077s snap-code-61.mount
7.040s switcheroo-control.service
7.033s systemd-logind.service
6.921s dev-loop18.device
6.777s systemd-rfkill.service
6.601s snap-core-10908.mount
6.601s dev-loop17.device
6.594s snap-core-10958.mount
6.560s dev-loop16.device
6.428s dev-loop15.device
6.300s snap-core18-1988.mount
6.254s dev-loop14.device
6.099s dev-loop13.device
5.847s dev-loop11.device
5.833s dev-loop12.device
5.708s snap-core18-1997.mount
5.666s snap-core20-904.mount
5.582s dev-loop7.device
5.581s dev-loop10.device
5.447s gpu-manager.service
5.249s dev-loop0.device
5.245s dev-loop6.device
5.221s dev-loop2.device
5.058s dev-loop4.device
4.911s dev-loop1.device
4.811s dev-loop3.device
4.639s dev-loop5.device
4.619s grub-common.service
4.600s apt-daily-upgrade.service
4.562s apport.service
4.118s e2scrub_reap.service
3.602s rsyslog.service
3.221s systemd-tmpfiles-clean.service
2.904s snap-core20-975.mount
2.877s snap-freecad-19.mount
2.866s snap-freecad-22.mount
2.831s snapd.apparmor.service
2.609s lxc-net.service
2.208s apparmor.service
1.777s snap-gnome\x2d3\x2d28\x2d1804-145.mount
1.776s snap-gnome\x2d3\x2d34\x2d1804-60.mount
1.771s snap-gnome\x2d3\x2d34\x2d1804-66.mount
1.702s snap-go-7013.mount
1.700s snap-go-7221.mount
1.693s snap-gradle-59.mount
1.680s snap-gradle-78.mount
1.678s snap-gtk\x2dcommon\x2dthemes-1513.mount
1.677s snap-gtk\x2dcommon\x2dthemes-1514.mount
1.675s snap-htop-2069.mount
1.660s snap-htop-2185.mount
1.622s snap-kde\x2dframeworks\x2d5\x2dcore18-32.mount
1.617s lxc.service
1.608s snap-ncspot-85.mount
1.600s snap-nmap-2254.mount
1.567s snap-nmap-2280.mount
1.563s grub-initrd-fallback.service
1.535s snap-notepad\x2dplus\x2dplus-258.mount
1.524s snap-notepad\x2dplus\x2dplus-260.mount
1.510s snap-pdftk-9.mount
1.508s snap-snap\x2dstore-518.mount
1.507s snap-snapd-11402.mount
1.499s snap-snapd-11588.mount
1.459s snap-spt-264.mount
1.458s snap-spt-271.mount
1.436s snap-telegram\x2dcli-34.mount
1.429s systemd-resolved.service
1.399s snap-telegram\x2ddesktop-2480.mount
1.384s snap-telegram\x2ddesktop-2551.mount
1.068s phpsessionclean.service
1.054s systemd-udevd.service
1.024s kerneloops.service
987ms pppd-dns.service
954ms upower.service
945ms systemd-backlight@backlight:intel_backlight.service
941ms systemd-udev-trigger.service
889ms systemd-modules-load.service
794ms lm-sensors.service
785ms systemd-user-sessions.service
761ms swapfile.swap
702ms systemd-tmpfiles-setup-dev.service
635ms systemd-sysusers.service
605ms systemd-tmpfiles-setup.service
577ms plymouth-quit.service
541ms systemd-sysctl.service
457ms dev-hugepages.mount
456ms dev-mqueue.mount
455ms sys-kernel-debug.mount
453ms keyboard-setup.service
453ms systemd-journald.service
452ms kmod-static-nodes.service
451ms [email protected]
442ms systemd-fsck@dev-disk-by\x2duuid-E3EC\x2dEBB0.service
417ms snap-tetris\x2dthefenriswolf-4.mount
400ms atopacct.service
399ms snap-tizonia-482.mount
398ms snap-tizonia-503.mount
350ms setvtrgb.service
344ms systemd-timesyncd.service
300ms rtkit-daemon.service
275ms plymouth-start.service
260ms sddm.service
226ms bluetooth.service
205ms systemd-random-seed.service
201ms console-setup.service
201ms snap-vlc-2103.mount
192ms snap-wine\x2dplatform\x2d5\x2dstable-16.mount
166ms apport-autoreport.service
160ms plymouth-read-write.service
152ms snap-wine\x2dplatform\x2druntime-216.mount
149ms [email protected]
145ms snap-wine\x2dplatform\x2druntime-212.mount
130ms boot-efi.mount
124ms systemd-remount-fs.service
101ms snapd.seeded.service
88ms openvpn.service
56ms systemd-update-utmp.service
46ms cpufrequtils.service
41ms motd-news.service
27ms vboxweb-service.service
26ms [email protected]
25ms vboxballoonctrl-service.service
24ms vboxautostart-service.service
7ms alsa-restore.service
6ms systemd-update-utmp-runlevel.service
4ms sys-fs-fuse-connections.mount
3ms sys-kernel-config.mount
596us snapd.socket
从这里我可以看到
1分钟20.804秒vboxdrv.service39.768
秒snapd.service33.076
秒dev-sda6.device21.262
秒networkd-dispatcher.service16.373秒
udisks2.service
很可能是罪魁祸首，现在有办法禁用它们吗？我应该完全禁用它们吗？我有一个 /dev/sda6，所以我认为不应该禁用它。
$ 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 @2min 4.885s
└─multi-user.target @2min 4.885s
└─vboxweb-service.service @2min 4.858s +27ms
└─network-online.target @1min 9.043s
└─NetworkManager-wait-online.service @56.838s +12.204s
└─NetworkManager.service @43.973s +12.864s
└─dbus.service @43.970s
└─basic.target @43.948s
└─sockets.target @43.948s
└─snapd.socket @43.948s +596us
└─sysinit.target @43.868s
└─snapd.apparmor.service @41.036s +2.831s
└─apparmor.service @38.813s +2.208s
└─local-fs.target @38.812s
└─run-snapd-ns-anbox.mnt.mount @58.454s
└─run-snapd-ns.mount @57.779s
└─local-fs-pre.target @7.442s
└─systemd-tmpfiles-setup-dev.service @6.739s +702ms
└─systemd-sysusers.service @6.102s +635ms
└─systemd-remount-fs.service @5.215s +124ms
└─systemd-journald.socket @4.761s
└─system.slice @4.757s
└─-.slice @4.757s
如果您需要更多信息，请告诉我，我会添加。
编辑：
我的 dmesg 输出（太大因此 pastebin 链接）：https://pastebin.com/E1DdC5rT