optimizing system boot time on fedora26

Fedora 26 uses grub2 as default boot loader , and traditional sequential init daemon is replaced by systemd start up daemon which can start servuce simultaneously.

there are situations where boot times are longer than expected.
Best way is to start analying the time taken by the process to start this can be checked by systemctl-analyze
comamnd.

#systemd-analyze 
Startup finished in 2.685s (kernel) + 6.928s (initrd) + 1min 4.830s (userspace) = 2min 13.443s

The same above can be exported as an image and boot times can be investigated

#systemd-analyze plot > boot.svg
#systemd-analyze blame 
         37.894s abrtd.service
         25.961s docker.service
         18.333s tuned.service
         14.288s plymouth-quit-wait.service
         12.432s sssd.service
         10.672s libvirtd.service
         10.296s firewalld.service
          9.284s NetworkManager-wait-online.service
          7.816s lvm2-monitor.service
          6.750s systemd-udev-settle.service
          4.856s dev-sdb3.device
          4.565s udisks2.service
          4.276s polkit.service
          4.013s initrd-switch-root.service
          3.485s systemd-journal-flush.service
          2.941s gssproxy.service
          2.520s rsyslog.service
          2.520s netcf-transaction.service
          2.477s ModemManager.service
          2.045s lightdm.service
          1.921s dracut-initqueue.service
          1.669s systemd-fsck-root.service
          1.622s nagios.service
          1.596s avahi-daemon.service
          1.544s chronyd.service
          1.461s thermald.service
          1.428s systemd-vconsole-setup.service
          1.300s fedora-readonly.service
          1.226s sshd.service
          1.203s bluetooth.service
          1.123s proc-sys-fs-binfmt_misc.mount
          1.107s systemd-tmpfiles-setup-dev.service
          1.072s sysstat.service
          1.060s dnf-makecache.service
          1.056s systemd-udevd.service
           844ms lm_sensors.service
           802ms tmp.mount
           744ms livesys.service
           736ms rtkit-daemon.service
           712ms switcheroo-control.service
           679ms NetworkManager.service
           648ms accounts-daemon.service
           599ms upower.service
           596ms systemd-user-sessions.service
           560ms dev-mqueue.mount
           509ms wpa_supplicant.service
           499ms systemd-remount-fs.service
           495ms auditd.service
           459ms tlp.service

from the above we can see that abrtd , sssd services are taking longer duration during boot.
abrtd is a crash reporting tool it is safe to disable this service if you dont want to have crash reporting enabled.

#systemctl stop abrtd
#systemctl disable abrtd

sssd service is mainly used for remote directory authentication like ldap , freeIpa services if you are not using ldap its safe to disable the service.

#systemctl stop sssd.service 
#systemctl disable sssd.service 
Removed /etc/systemd/system/multi-user.target.wants/sssd.service

We can even use systemd-analyze critical-chain to see the boot chain process
systemd-analyze critical-chain
The time after the unit is active or started is printed after the “@” character.
The time the unit takes to start is printed after the “+” character.

$systemd-analyze
graphical.target @1min 4.366s
└─multi-user.target @1min 4.366s
  └─docker.service @38.404s +25.961s
    └─network-online.target @38.396s
      └─NetworkManager-wait-online.service @29.109s +9.284s
        └─NetworkManager.service @27.559s +679ms
          └─network-pre.target @27.556s
            └─firewalld.service @17.259s +10.296s
              └─polkit.service @12.820s +4.276s
                └─basic.target @12.658s
                  └─sockets.target @12.658s
                    └─cockpit.socket @12.614s +43ms
                      └─sysinit.target @12.558s
                        └─systemd-update-utmp.service @12.523s +33ms
                          └─auditd.service @12.025s +495ms
                            └─systemd-tmpfiles-setup.service @11.648s +361ms
                              └─fedora-import-state.service @11.448s +197ms
                                └─local-fs.target @11.440s
                                  └─var-lib-docker-plugins.mount @52.068s
                                    └─local-fs-pre.target @11.006s
                                      └─lvm2-monitor.service @3.189s +7.816s
                                        └─lvm2-lvmetad.service @10.667s
                                          └─lvm2-lvmetad.socket @3.184s
                                            └─-.mount
                                              └─system.slice
                                                └─-.slice

Analyzing boot time after disabling services.

#systemd-analyze 
Startup finished in 2.701s (kernel) + 5.342s (initrd) + 1min 12.818s (userspace) = 1min 20.861s