This article shows how to reduce boot time for Fedora 17, but the recipe can also be applied to 18, 19 and 20.

The target is to get a fast booting system with NetworkManager running and gdm displaying the login screen as fast as possible.

The system I use here is a Lenovo T420s (2x2x Intel(R) Core(TM) i5-2540M CPU @ 2.60GHz) with an INTEL SSDSA2BW160G3L harddrive.

First we choose a manual disk layout and use primary partitions and format them with ext4. In my case this results in:

sda2 swap sda3 ext4

After the first boot, setup of the user, etc. and 2 reboots (always reboot 2 times, before taking the measurement, because readahead needs to adapt to the changed boot process). First we update everything.

$ sudo yum update

After the reboots, I get:

$ systemd-analyze Startup finished in 1413ms (kernel) + 2911ms (initramfs) + 10593ms (userspace) = 14918ms

Because I don't use any LVM, RAID or encrypted devices, I can safely turn off all nearly all fedora-\*storage\* services. To turn off these services, we use the systemctl mask command. A bonus with that mechanism is, that no rpm %post script turns them on automatically.

$ cd /lib/systemd/system $ for i in fedora * storage * lvm2-monitor. * mdmonitor * . *; \ do sudo systemctl mask $ i ; \ done

On Fedora 17, it seems there are still some SysV initscripts left, so we turn them off:

$ for i in livesys livesys-late spice-vdagentd ; \ do sudo chkconfig $ i off ; \ done

Seems like we saved half of the time in userspace:

$ systemd-analyze Startup finished in 1640ms (kernel) + 6556ms (userspace) = 8197ms

From now on, you really have to know what you are doing and how to revert your actions. To compare Fedora with e.g. Ubuntu, I will now turn off all services except NetworkManager. The result will be a Linux system without mail, firewall, printing, the abrt tools, avahi, some mountpoints, rsyslog, irqbalance, and selinux security.

$ cd /lib/systemd/system $ for i in abrt * .service auditd.service avahi-daemon. * \ bluetooth. * dev-hugepages.mount dev-mqueue.mount \ fedora-configure.service fedora-loadmodules.service \ fedora-readonly.service ip6tables.service \ iptables.service irqbalance.service mcelog.service \ rsyslog.service sendmail.service sm-client.service \ sys-kernel-config.mount sys-kernel-debug.mount ; do \ sudo systemctl mask "$ i " ; \ done

To disable selinux (only for measurements!), edit /etc/selinux/config and add selinux=0 to the kernel command line.

My /etc/grub2.cfg now looks like this:

linux /vmlinuz-3.3.7-1.fc17.x86_64 root=/dev/sda3 rootfstype=ext4 libahci.ignore_sss=1 raid=noautodetect selinux=0 initrd /initramfs-3.3.7-1.fc17.x86_64.img

Now we are really fast!

$ systemd-analyze Startup finished in 1329ms (kernel) + 1596ms (userspace) = 2926ms

I also like the idea of automounting (systemd's automount feature was an idea of mine :-). So I turn /boot in a "mount on demand" mountpoint. Also having /tmp as a tmpfs is one way to reduce disk activity (useful for e.g. a slow flash disk). My resulting /etc/fstab looks like this:

/dev/sda3 / ext4 defaults 1 1 /dev/sda1 /boot ext4 noauto,comment=systemd.automount 1 2 /dev/sda2 swap swap defaults 0 0 tmpfs /tmp tmpfs defaults 0 0

This only saved a little bit of time, but still:

$ systemd-analyze Startup finished in 1342ms (kernel) + 1426ms (userspace) = 2769ms

Because NetworkManager is started also by the graphical login target, I can remove it from the multi-user target and it will be started in parallel to the gdm login screen.

$ sudo rm /etc/systemd/system/multi-user.target.wants/NetworkManager.service

This will shave of a few milliseconds:

$ systemd-analyze Startup finished in 1323ms (kernel) + 1279ms (userspace) = 2603ms

To see the difference readahead makes for the system, I turn it off temporarily and reboot

$ cd /lib/systemd/system $ for i in * readahead *; do sudo systemctl mask $ i ;done

Which will give us:

$ systemd-analyze Startup finished in 1336ms (kernel) + 1210ms (userspace) = 2547ms

This time is a little bit misleading. Although it seems faster, the real time until the login screen is displayed is taking longer. So a fair comparison would involve a stopwatch.

To turn off plymouth, because we want speed and not eye candy, I remove plymouth completely and regenerate the initramfs to get rid of it.

$ sudo yum remove 'plymouth*' $ sudo dracut -f

After a reboot we get the stunning result of:

$ systemd-analyze Startup finished in 612ms (kernel) + 499ms (initramfs) + 1330ms (userspace) = 2443ms

The nice thing about systemctl mask is, that you can always unmask it via systemctl unmask and only enable those default services, which you really need.

Now, turn selinux back on, edit /etc/selinux/config and remove selinux=0 from the kernel command line. You really don't want to trade some seconds for security!

Have fun and happy rebooting!

And don't forget to reboot twice to let the readahead optimization kick in!