我的 ubuntu 启动非常慢。我将在这里展示dmesg启动时间差异大于一秒的摘录。
这些条目中哪一个是重要的，哪一个不是？（就规范而言。我自己可以看到最后的条目具有最大的时间差异，但对于未经训练的人来说，不清楚这是否在正常公差范围内）。我能做些什么呢？
[ 3.339708] systemd[1]: RTC configured in localtime, applying delta of 120 minutes to system time.
[ 4.001290] systemd[1]: systemd 229 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ -LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD -IDN)
[ 4.018390] systemd[1]: Set hostname to <foo-bar>.
[ 6.087475] systemd[1]: Reached target User and Group Name Lookups.
[ 11.484565] Adding 16646140k swap on /dev/sda6. Priority:-1 extents:1 across:16646140k FS
[ 13.358114] audit: type=1400 audit(1466263617.866:2): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/bin/ubuntu-core-launcher" pid=630 comm="apparmor_parser"
[ 13.644036] audit: type=1400 audit(1466263618.150:11): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/lib/NetworkManager/nm-dhcp-client.action" pid=627 comm="apparmor_parser"
[ 15.866759] cgroup: new mount options do not match the existing superblock, will be ignored
[ 19.540776] ------------[ cut here ]------------
[ 19.540829] WARNING: CPU: 1 PID: 847 at /build/linux-oXTOqc/linux-4.4.0/drivers/gpu/drm/i915/intel_display.c:1144 intel_disable_pipe+0x2b6/0x2c0 [i915]()
[ 19.784310] [drm:drm_edid_block_valid [drm]] *ERROR* EDID checksum is invalid, remainder is 140
[ 26.762481] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 27.020066] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 28.554052] e1000e: eth0 NIC Link is Up 100 Mbps Full Duplex, Flow Control: None
[ 28.554057] e1000e 0000:00:19.0 eth0: 10/100 speed: disabling TSO
[ 28.554090] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 290.868877] show_signal_msg: 48 callbacks suppressed
[ 290.868883] cal-client-dbus[3618]: segfault at 4330443618 ip 00007f0886c485a9 sp 00007f0855ffa350 error 4 in libc-2.23.so[7f0886bca000+1c0000]
[ 644.443348] [drm:intel_set_pch_fifo_underrun_reporting [i915]] *ERROR* uncleared pch fifo underrun on pch transcoder B
[ 644.443375] [drm:intel_pch_fifo_underrun_irq_handler [i915]] *ERROR* PCH transcoder B FIFO underrun
[ 831.364787] gvfsd-dnssd[9183]: segfault at 0 ip 00007fb336559b5a sp 00007fff12abefd8 error 4 in libc-2.23.so[7fb3364bb000+1c0000]
[ 831.546627] gvfsd-dnssd[9181]: segfault at 0 ip 00007f59f4fd3b5a sp 00007ffcfd0ed1b8 error 4 in libc-2.23.so[7f59f4f35000+1c0000]
我的版本：
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04 LTS
Release: 16.04
Codename: xenial
输出systemd-analyze blame
1min 2.716s sendmail.service
15.367s teamviewerd.sysv.service
9.686s NetworkManager-wait-online.service
9.153s lightdm.service
7.907s ModemManager.service
6.312s squid.service
5.912s NetworkManager.service
5.891s systemd-tmpfiles-setup.service
5.492s apparmor.service
5.353s dev-sda5.device
5.090s accounts-daemon.service
4.280s gpu-manager.service
3.236s console-kit-log-system-start.service
3.185s systemd-logind.service
3.148s pppd-dns.service
3.148s selfcontrol.service
3.092s irqbalance.service
3.069s grub-common.service
2.940s speech-dispatcher.service
2.260s rsyslog.service
1.722s plymouth-start.service
1.695s avahi-daemon.service
1.265s apt-daily.service
1.162s polkitd.service
1.128s ondemand.service
975ms systemd-journald.service
945ms systemd-tmpfiles-setup-dev.service
888ms systemd-udevd.service
872ms colord.service
765ms thermald.service
696ms apport.service
672ms systemd-modules-load.service
642ms ssh.service
633ms networking.service
588ms kmod-static-nodes.service
588ms ufw.service
587ms sys-kernel-debug.mount
586ms dev-mqueue.mount
586ms dev-hugepages.mount
556ms upower.service
498ms systemd-user-sessions.service
495ms console-kit-daemon.service
440ms udisks2.service
427ms console-setup.service
330ms systemd-udev-trigger.service
314ms dns-clean.service
247ms systemd-random-seed.service
226ms iio-sensor-proxy.service
212ms systemd-journal-flush.service
154ms systemd-sysctl.service