优化 Ubuntu 20.04 的启动时间可以从多个方面入手，以下是详细的步骤和建议：
一、分析启动耗时
首先检查系统启动各阶段的耗时：
systemd-analyze time # 查看整体启动时间
systemd-analyze blame # 列出各服务/进程的启动耗时
systemd-analyze critical-chain # 查看关键路径的启动链
二、禁用不必要的服务
禁用启动时不需要的系统服务：
sudo systemctl disable <service-name> # 禁用服务（如蓝牙、打印机等）
sudo systemctl mask <service-name> # 彻底屏蔽服务（谨慎使用）
常见可禁用的服务：
bluetooth.service（蓝牙）cups.service（打印机）ModemManager.service（调制解调器）networkd-dispatcher.service（若使用NetworkManager）accounts-daemon.service（用户账户管理）
三、优化文件系统检查（fsck）
-
减少文件系统检查频率：
- 编辑
/etc/fstab，将最后一列的数值改为0（表示不检查）：sudo nano /etc/fstab # 示例：将最后数字从 1 或 2 改为 0 UUID=xxxx / ext4 defaults,noatime,discard 0 0 - 使用
noatime或relatime挂载选项减少磁盘写入。
- 编辑
-
禁用启动时的文件系统等待：
sudo systemctl disable systemd-fsck-root.service
四、调整内核参数
-
编辑 GRUB 配置：
sudo nano /etc/default/grub # 修改以下参数： GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" # 添加或修改为（例如）： GRUB_CMDLINE_LINUX_DEFAULT="quiet splash noresume fsck.mode=skip"fsck.mode=skip：跳过文件系统检查（谨慎使用）。noresume：如果未使用休眠功能。
-
更新 GRUB：
sudo update-grub
五、优化 SSD 性能（如使用 SSD）
- 启用 TRIM：
sudo systemctl enable fstrim.timer - 确认是否已启用
discard选项（在/etc/fstab中添加discard）。
六、清理启动项
- 管理用户级启动程序：
gnome-session-properties # 图形界面管理启动项 - 清理旧内核：
sudo apt autoremove --purge # 删除旧内核和依赖
七、排查硬件问题
- 检查硬盘健康状况：
sudo smartctl -a /dev/sda - 检查日志中的硬件错误：
journalctl -b -p 3 # 查看本次启动的错误日志
八、使用轻量化组件
- 替换图形界面为轻量级桌面（如 Xfce 或 LXQt）。
- 使用更快的显示管理器（如
lightdm替代gdm3）：sudo apt install lightdm sudo dpkg-reconfigure lightdm
九、其他优化
- 减少 GRUB 等待时间：
sudo nano /etc/default/grub GRUB_TIMEOUT=2 # 将默认超时时间改为2秒 sudo update-grub - 预加载内核模块：
- 将常用模块添加到
/etc/modules-load.d/modules.conf。
- 将常用模块添加到
十、验证优化结果
重启后再次运行：
systemd-analyze time
systemd-analyze blame
通过以上步骤，大部分情况下可以显著缩短启动时间。如果问题依旧存在，可能需要进一步排查特定服务或硬件兼容性问题。
我的结果:
- 最开始的时候：
> systemd-analyze time
Startup finished in 22.227s (firmware) + 9.423s (loader) + 36.324s (kernel) + 1min 51.738s (userspace) = 2min 59.713s
graphical.target reached after 1min 51.722s in userspace
> systemd-analyze blame
20.870s plymouth-quit-wait.service >4.621s NetworkManager-wait-online.service >3.019s dev-sda2.device >1.329s fwupd.service >459ms docker.service >391ms snapd.service >387ms man-db.service >305ms blueman-mechanism.service >299ms systemd-logind.service >278ms dev-loop0.device >267ms logrotate.service >264ms upower.service >255ms snap-core22-1722.mount >241ms snap-core20-2496.mount >239ms dev-loop2.device >235ms snap-gnome\x2d3\x2d28\x2d1804-198.mount >234ms containerd.service >232ms snap-gnome\x2d3\x2d38\x2d2004-143.mount >232ms snap-gnome\x2d42\x2d2204-176.mount >229ms snap-gnome\x2d42\x2d2204-202.mount >227ms snap-gtk\x2dcommon\x2dthemes-1535.mount >226ms dev-loop11.device >> 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 @1min 51.722s
└─multi-user.target @1min 51.722s└─kerneloops.service @1min 35.442s +13ms└─nss-lookup.target @1min 35.440s└─todeskd.service @1min 35.439s└─network-online.target @1min 35.436s└─NetworkManager-wait-online.service @1min 30.814s +4.621s└─NetworkManager.service @1min 30.736s +71ms└─dbus.service @1min 30.733s└─basic.target @1min 30.712s└─sockets.target @1min 30.712s└─uuidd.socket @1min 30.710s└─sysinit.target @1min 30.699s└─systemd-timesyncd.service @3.507s +97ms└─systemd-tmpfiles-setup.service @3.486s +16ms└─systemd-journal-flush.service @562ms +106ms└─systemd-journald.service @458ms +103ms└─systemd-journald.socket @451ms└─system.slice @445ms└─-.slice @445ms- 优化了一下启动项的图像加载，禁用了plymouth图像加载
5263 sudo systemctl mask plymouth-quit-wait.service5264 sudo apt remove plymouth5265 sudo nano /etc/default/grub5266 sudo update-grub
> systemd-analyze time
Startup finished in 20.682s (firmware) + 5.135s (loader) + 4.417s (kernel) + 1min 37.067s (userspace) = 2min 7.302s
graphical.target reached after 1min 37.059s in userspace
> systemd-analyze blame
4.897s NetworkManager-wait-online.service >
1.456s fwupd.service >
1.328s docker.service >711ms dev-sda2.device >681ms snapd.seeded.service >620ms man-db.service >594ms snapd.service >504ms networkd-dispatcher.service >419ms blueman-mechanism.service >322ms dev-loop0.device >298ms dev-loop1.device >298ms apport-autoreport.service >293ms containerd.service >292ms dev-loop2.device >287ms upower.service >279ms logrotate.service >270ms systemd-logind.service >269ms dev-loop4.device >256ms dev-loop8.device >252ms dev-loop10.device >249ms dev-loop5.device >247ms dev-loop6.device >242ms accounts-daemon.service >241ms dev-loop3.device >236ms snap-core18-2846.mount >232ms fstrim.service >221ms udisks2.service >218ms snap-gnome\x2d42\x2d2204-176.mount >217ms snap-gnome\x2d42\x2d2204-202.mount >213ms dev-loop9.device >213ms dev-loop11.device >208ms snap-snap\x2dstore-1113.mount >205ms snap-snapd-23545.mount >204ms dev-loop17.device >204ms dev-loop18.device >204ms snap-snapd-23771.mount >197ms dev-loop16.device >197ms dev-loop7.device >188ms dev-loop15.device >186ms systemd-resolved.service >185ms smartmontools.service >182ms snap-core20-2496.mount >180ms snap-core22-1722.mount >179ms snap-core22-1748.mount >175ms snap-gnome\x2d3\x2d38\x2d2004-119.mount >172ms dev-loop13.device >172ms snap-snap\x2dstore-1216.mount >168ms systemd-timesyncd.service >165ms snap-notion\x2dsnap\x2dreborn-49.mount >164ms dev-loop14.device >161ms dev-loop12.device >150ms lm-sensors.service >146ms apparmor.service >136ms systemd-udev-trigger.service >136ms gpu-manager.service >135ms ModemManager.service >134ms snap-core18-2855.mount >120ms avahi-daemon.service >116ms bluetooth.service >116ms systemd-journal-flush.service >114ms snap-gtk\x2dcommon\x2dthemes-1535.mount >111ms NetworkManager.service >110ms snap-notion\x2dsnap\x2dreborn-50.mount >109ms systemd-journald.service >103ms polkit.service >> 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 @1min 37.059s
└─multi-user.target @1min 37.059s└─docker.service @1min 35.730s +1.328s└─nss-lookup.target @1min 35.729s└─todeskd.service @1min 35.729s└─network-online.target @1min 35.726s└─NetworkManager-wait-online.service @1min 30.829s +4.897s└─NetworkManager.service @1min 30.714s +111ms└─dbus.service @1min 30.708s└─basic.target @1min 30.688s└─sockets.target @1min 30.688s└─snapd.socket @1min 30.686s +1ms└─sysinit.target @1min 30.671s└─systemd-timesyncd.service @1.249s +168ms└─systemd-tmpfiles-setup.service @1.207s +37ms└─systemd-journal-flush.service @584ms +116ms└─systemd-journald.service @473ms +109ms└─systemd-journald.socket @466ms└─system.slice @461ms└─-.slice @461ms
