Reducing ubuntu boot time using dmesg

Question

The boot time is 141 seconds. Here's the most interesting parts of dmesg command:

[    2.870498] usb 1-1.2: new high-speed USB device number 5 using ehci_hcd
[   80.669210] ADDRCONF(NETDEV_UP): eth0: link is not ready

I takes 78

[   86.108371] intel ips 0000:00:1f.6: i915 driver attached, reenabling gpu turbo
[  102.924783] cfg80211: All devices are disconnected, going to restore regulatory settings

16 more seconds

[  109.643299] wlan0: associated
[  140.406853] wlan0: deauthenticated from 00:3a:9a:49:27:60 (Reason: 23)

and 31 seconds.

Is it possible to do something with these parts in order to reduce total boot time?

Answer 1

Here is my guess on what is happening:

[    2.870498] usb 1-1.2: new high-speed USB device number 5 using ehci_hcd

The kernel finishes initializing. After this, upstart takes over and begins starting userspace applications.

[   80.669210] ADDRCONF(NETDEV_UP): eth0: link is not ready

The network-manager service is started.

[   86.108371] intel ips 0000:00:1f.6: i915 driver attached, reenabling gpu turbo

The Xserver starts which initializes the graphics driver. At this point, I would consider the machine "booted", as most of the services should be started.

[  102.924783] cfg80211: All devices are disconnected, going to restore regulatory settings
[  109.643299] wlan0: associated
[  140.406853] wlan0: deauthenticated from 00:3a:9a:49:27:60 (Reason: 23)

Network-manager connects to your access point. This may not occur until after you have logged in and nm-applet is started.

I recommend using bootchart to get a real breakdown instead of this guessing.