The "exe" process on slow Ubuntu bootchart

Ubuntu 11.10 does already a good job at starting faster, but if you’ve read one of my previous posts on Ubuntu startup time [1] then you know that there is always something to be tweaked for better or for worse. Part of the process is to defer services that are not needed immediately (i.e. printing) to a time after the display manager has loaded. At that time the subjective impression the user must have is that the boot process has finished, hence the time required for such services to start does not count any more against boot time.

At some point it turned out that the boot process was slowed down significantly by a long lasting “exe” process right after the kernel had started as shown by bootchart

Since there isn’t any script or executable named exe either on the root file system or in the initrd image and the issue didn’t pop up on the interweb either (at the time of writing the only remotely relevant post I found is about someone noticing the same process and being afraid of having caught a Windows virus) the reason for this was not quite clear. A glance at the I/O meter in bootchart reveals that there is some file system activity on the boot drive, which turns out to be a fsck.

The shutdown logs revealed this:

Unmounting local filesystems
/ is busy

Now the story starts making sense: the root file system could not be unmounted, thus it undergoes a file system check on every next boot – that is the long exe process depicted in bootchart.

The cause was one of the services deferred earlier, so I just made sure it shuts down earlier in the tear down sequence and everything works fine again.

Resources

[1] Speeding up Ubuntu 11.04 boot time
http://georgovassilis.blogspot.com/2011/05/speeding-up-ubuntu-1104-boot-time.html

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