我的开机时间太长了。我使用了systemd-analyze blame命令，结果如下：
dimitrios@dimitrios-A15:~/Downloads$ systemd-analyze blame
1min 4.487s apt-daily.service
22.627s dev-sda4.device
11.789s systemd-udevd.service
9.863s NetworkManager-wait-online.service
5.549s apache2.service
5.411s ModemManager.service
5.028s grub-common.service
4.334s systemd-tmpfiles-setup-dev.service
3.899s accounts-daemon.service
3.563s thermald.service
3.413s NetworkManager.service
3.084s iio-sensor-proxy.service
2.770s vboxdrv.service
2.238s keyboard-setup.service
2.089s irqbalance.service
1.961s binfmt-support.service
1.940s quota.service
1.865s bluetooth.service
1.802s dev-hugepages.mount
1.802s sys-kernel-debug.mount
1.711s dev-mqueue.mount
1.618s systemd-logind.service
1.596s gpu-manager.service
1.574s console-setup.service
1.516s udisks2.service
1.480s colord.service
1.480s upower.service
1.448s rsyslog.service
1.334s ofono.service
1.304s ondemand.service
1.303s systemd-modules-load.service
1.297s speech-dispatcher.service
1.297s console-kit-log-system-start.service
1.269s laptop-mode.service
1.268s pppd-dns.service
1.246s systemd-user-sessions.service …