# Ureadahead

Ureadahead (Über-readahead) is used to speed up the boot process. It works by reading all the files required during boot and makes pack files for quicker access, then during boot reads these files in advance, thus minimizes the access times for the harddrives. It's intended to replace sreadahead.

## Requirements

Ureadahead needs a kernel patch to work, which is no longer available on the AUR.

The user-space package is called ureadahead.

## How it works

When run without any arguments, ureadahead checks for pack files in /var/lib/ureadahead, and if none are found or if the packfiles are older than a month, it starts tracing the boot process. When tracing, it waits for either a TERM or INT signal before generating the pack file.

Otherwise, if the file is up to date, it just reads the pack file in preparation for the boot.

It works for both SSDs and traditional harddrives and automatically optimizes the pack files depending on which you have.

## Using ureadahead

First you need the patched kernel. After the installation you need to make ureadahead start on boot. Simply create the file `/etc/rc.d/functions.d/ureadahead` and add:

    ureadahead() {
    /sbin/ureadahead --timeout=240 &
    }

    add_hook sysinit_end ureadahead

to start it after sysinit.

Note: You can also use `sysinit_premount` to start it before it mounts all the other filesystems in `/etc/fstab`, but this might create issues depending on your system (e.g. if you have `/var` on a separate partition).

Now you should be good to go.

## Configuration

There are few configuration options for ureadahead. You can specify which mountpoint to trace with:

    $ ureadahead /<mountpoint>

though it should automatically trace all needed mountpoints during boot.

You can also run it with `--force-trace` to force a retrace, however it is better to remove the pack files and reboot.

The pack files are in `/var/lib/ureadahead` and are named after their mountpoint (i.e. `pack` for root, `home.pack` for `/home`).

## Questions

### Why does this take so long time tracing?

If you didn't supply --timeout, you need to kill it manually. Either just `^C` it, or use `pkill ureadahead`.

## Helping out

If your boot actually becomes slower after generating the pack files and you're sure ureadahead is to blame, then file a bug report. To get useful data, make sure both ureadahead and bootchart installed.

First, disable ureadahead on boot (remove `/etc/rc.d/functions.d/ureadahead`) and remove the pack files in `/var/lib/ureadahead`, then reboot and save the bootchart.

Then, reenable ureadahead (recreate the file in `/etc/rc.d/functions.d/ureadahead`) and reboot. Save this bootchart too.

Finally, reboot once more, and save the final bootchart.

Now you should have 3 bootcharts, one without ureadahead, one when ureadahead is tracing and one when it's running normally. Then, as root, run:

    # ureadahead --dump > ureadahead.dump

to dump the contents of the pack file. Create a bug report on the ureadahead launchpad file and attach the bootcharts along with the dump.

Note: I do not know how welcome this will be to the ubuntu developers, since we're using arch. If you still want to help, give it a try and see if they're interested.

## More resources

- ureadahead homepage
- ureadahead package on AUR
- Nvidia driver for the patched kernel

Category:

- Boot process