我在一台 HP 笔记本电脑上使用 Ubuntu 18.04，该笔记本电脑双启动 Windows 10，Ubuntu 有 40 GB 的磁盘空间，SWAP 区域有 20 GB，因为我有 8 GB 的 RAM。我使用的是 HDD。在 40 GB 中，32.5 GB 仍然可用且免费。几周前我刚刚安装了操作系统。关机时间很短，大约 5 秒，但启动所需的时间长达 1 分钟。我已经编辑/etc/initramfs-tools/initramfs.conf和更改了MODULES=dep。这大大减少了 initramfs 所花费的时间。我不确定如何改进它并减少所花费的时间。
启动时间从systemd-analyze blame：
23.512s dev-sda6.device
21.462s plymouth-quit-wait.service
18.832s systemd-udevd.service
18.395s apparmor.service
17.486s systemd-tmpfiles-setup.service
6.801s NetworkManager-wait-online.service
6.732s plymouth-start.service
5.873s plymouth-read-write.service
4.169s udisks2.service
3.890s networking.service
3.889s accounts-daemon.service
3.013s speech-dispatcher.service
2.573s networkd-dispatcher.service
2.527s NetworkManager.service
2.453s avahi-daemon.service
2.449s thermald.service
2.446s alsa-restore.service
2.446s systemd-logind.service
2.443s pppd-dns.service
2.438s gpu-manager.service
2.434s rsyslog.service
2.016s apport.service
1.426s wpa_supplicant.service
1.388s dns-clean.service
1.276s grub-common.service
1.269s keyboard-setup.service
1.056s tlp.service
1.007s systemd-random-seed.service
987ms packagekit.service
896ms fwupd.service
878ms systemd-tmpfiles-setup-dev.service
779ms systemd-remount-fs.service
758ms dev-mqueue.mount
714ms sys-kernel-debug.mount
712ms dev-hugepages.mount
694ms systemd-modules-load.service
590ms polkit.service
579ms iio-sensor-proxy.service
574ms systemd-sysctl.service
442ms colord.service
434ms systemd-journal-flush.service
379ms systemd-timesyncd.service
332ms dev-disk-by\x2duuid-72e62aa6\x2deefa\x2d49e1\x2daba3\x2d858b0e7dfbd3.swap
330ms upower.service
321ms systemd-journald.service
312ms systemd-backlight@backlight:intel_backlight.service
230ms setvtrgb.service
217ms ufw.service
209ms [email protected]
179ms systemd-resolved.service
174ms bolt.service
141ms gdm.service
106ms kmod-static-nodes.service
87ms console-setup.service
73ms systemd-update-utmp.service
56ms systemd-udev-trigger.service
52ms kerneloops.service
22ms systemd-user-sessions.service
20ms sys-fs-fuse-connections.mount
19ms rtkit-daemon.service
19ms sys-kernel-config.mount
8ms systemd-update-utmp-runlevel.service
free --human：
total used free shared buff/cache available
Mem: 7.7G 1.2G 5.4G 148M 1.1G 6.3G
Swap: 19G 0B 19G
输出ls /etc/apparmor.d/：
abstractions force-complain tunables usr.bin.man usr.lib.libreoffice.program.soffice.bin usr.sbin.cupsd usr.sbin.tcpdump
cache local usr.bin.evince usr.lib.libreoffice.program.oosplash usr.lib.libreoffice.program.xpdfimport usr.sbin.ippusbxd
disable sbin.dhclient usr.bin.firefox usr.lib.libreoffice.program.senddoc usr.sbin.cups-browsed usr.sbin.rsyslogd
笔记：
- 为了缩短所需时间，
systemd-journal-flush.service我将日志刷新服务使用的最大文件大小减少到 50M。 - sda6 是我在硬盘上安装 Ubuntu 的分区
- 我的机器不使用 Thunderbolt
- 我不使用 SSD
编辑：添加基准测试结果
sudo hdparm -Tt /dev/sda：
/dev/sda:
Timing cached reads: 11730 MB in 2.00 seconds = 5876.89 MB/sec
Timing buffered disk reads: 322 MB in 3.00 seconds = 107.22 MB/sec
sudo hdparm -v /dev/sda：
/dev/sda:
multcount = 16 (on)
IO_support = 1 (32-bit)
readonly = 0 (off)
readahead = 256 (on)
geometry = 121601/255/63, sectors = 1953525168, start = 0
dd if=/dev/zero of=/tmp/output bs=8k count=10k; rm -f /tmp/output：
10240+0 records in
10240+0 records out
83886080 bytes (84 MB, 80 MiB) copied, 0.0681511 s, 1.2 GB/s
