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I typed this command to remove a package and related configuration files:

sudo apt-get --purge remove supervisor 

The command ended without errors but I got this message:

ureadahead will be reprofiled on next reboot

What does it mean? Do I have (or is it suggested) to reboot?

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2 Answers 2

up vote 8 down vote accepted

There is no need to reboot or worry.

Ureadahead, actually called über-readahead, is a system to speed up boot times by preloading boot files into pages and memory so they are ready immediately while called upon, via pack files which are already pre-packed into memory-friendly pages. It will generate a plan for preload monthly, and when files related to boot are modified, added, or removed. Since it only affects boot performance, it is not necessary to reboot since ureadahead only applies during boot, and the boot packing will be done on next boot anyway. However, it will sometimes run even when boot files or the monthly cycle don't apply.

How it actually works:

ureadahead is an executable that will trace the boot process, and then generate pack files. When run without arguments, this executable checks /var/lib/ureadahead for packfiles and if they are old enough, or don't exist, it begins tracing forever. It can then be given a SIGTERM with Ctrl+C, at which time it will save any packfiles. It can also be run with --timeout to make it automatically stop and save its packfiles.

Ref: https://wiki.archlinux.org/index.php/Ureadahead

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über-readahead is used during boot to read files in advance of when they are needed such that they are already in the page cache, improving boot performance.

Its data files are regenerated on the first boot after install, and either monthly thereafter or when packages with init scripts or configs are installed or updated. You can refer to https://launchpad.net/ureadahead for more ingormation.

Now, as mentioned above, ureadhead files needs to be updated when packages with init scripts or configs are installed or updated. In your case, I guess the same has happened while removing the files. So ureadahead will regenerate its data files based on this removal operation.

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This answer is more simple to understand to me. Your question @Obsessive is a bit harder but more detailed and, finally really answer my final question Do I have (or is it suggested) to reboot? –  Guandalino Sep 30 '12 at 22:12
    
In fact I accepted your answer. –  Guandalino Sep 30 '12 at 22:15
    
@Guandalino Thanks for clarifying. –  hexafraction Sep 30 '12 at 22:16
    
@ObsessiveFOSS : When I initially started out to answer the question, you hadn't answered it. But, after posting, I found out that you had already replied. I thought of keeping my answer because I felt it was more simpler. Anyhow, I agree yours was a very detailed one. –  linuxandunix Oct 1 '12 at 3:32
    
@linuxandunix OK. No problem. It's within minutes, so it's OK/ –  hexafraction Oct 2 '12 at 0:06
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