Run boot processes in parallel
Concurrent booting allows Ubuntu to take advantage of
dual-core processors, as well as processors that hyperthread or
multithread.
You can take advantage of running boot processes in
parallel by editing the file /etc/init.d/rc in a text editor (with root
permissions e.g. sudo gedit /etc/init.d/rc) and locating the following
line:
CONCURRENCY=none
Change the line to:
CONCURRENCY=shell
Please note that this tip should not be used for systems
with single core processors. Whilst it won't affect the machine
booting,
you might find it actually degrades bootup time.
Reprofiling boot sequence
Ubuntu developers have done a good job in ensuring that the latest
distro releases boot up at a good rate. Nevertheless there is
more that you can do to quicken the process. For this tip, we will
explore profiling.
One reason why systems can be slow to boot is due to
excessive disk seeking. Fortunately, Linux has a mechanism called
"readahead" which minimises
this behavior. Profiling makes a list of all the files that are read
during bootup. It then sorts the files according to how they
are stored on the hard disk, saving the information into the
/etc/readahead folder. Whilst Ubuntu ships with a readahead
list, this is designed for the developers' own system, and is not tailored
to your computer and therefore does not reflect the additional services
you might want to load during bootup.
Once profiling has been completed, Ubuntu reads your
personalised /etc/readahead folder the next time the system is
rebooted. Consequently, files are read faster for all future restarts
of
the system.
To profile the system, perform the following actions:
- At the bootup menu (GRUB), select
the kernel you wish to profile (You may need to hit ESC to see the boot
menu)
- Press e to edit the
entry
- Select the line starting with kernel (or linux). Press
e
again
- Add the word profile to the end of
the
line
- Press b to boot (or Ctrl-X)
- Let the system boot to the login screen, and wait for
all disk
activity to stop. The system will boot slower whilst the profiling
takes place. This is normal
- Restart the system
The speed increase to the boot time is dependent on the
machine and how the files were already arranged on the hard disk.
Neverthless, in many cases users should see an appreciable improvement
in startup times.
Whilst this is a safe procedure, we would again recommend
that you make a backup of any important data on your machine before
proceeding.
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