从问题这里我找到了一种方法来弄清楚什么才是真正耗时的。输出systemd-analyze blame：
15.389s dev-sda5.device
15.159s snapd.service
15.133s plymouth-quit-wait.service
13.330s systemd-journal-flush.service
8.162s plymouth-start.service
8.073s NetworkManager-wait-online.service
7.582s systemd-udevd.service
7.220s systemd-sysctl.service
7.158s sys-fs-fuse-connections.mount
7.157s sys-kernel-config.mount
7.017s snap-gnome\x2dsystem\x2dmonitor-51.mount
6.959s snap-gnome\x2d3\x2d26\x2d1604-70.mount
6.914s snap-gnome\x2dcalculator-180.mount
6.887s snap-gnome\x2dcharacters-103.mount
6.827s snap-gnome\x2dlogs-37.mount
6.752s snap-gtk\x2dcommon\x2dthemes-319.mount
5.594s NetworkManager.service
5.035s ModemManager.service
4.721s grub-common.service
4.621s networkd-dispatcher.service
3.918s udisks2.service
3.670s dev-loop6.device
3.432s dev-loop2.device
3.299s accounts-daemon.service
2.778s wpa_supplicant.service
2.299s dev-loop5.device
2.219s dev-loop4.device
2.129s dev-loop3.device
[< 2s is skipped]
但真正需要的是什么？抱歉 - 我是 Ubuntu 新手...