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  1. I was wondering if the kernel choice during startup is equivalent to Ubuntu release choice? For example, I have installed 10.10. During startup, I can choose two kernels: 2.6.32 and 2.6.35. Does 2.6.32 mean 10.04 and 2.6.32 mean 10.10?
  2. Will applications installed under one kernel be also installed for other kernels available during startup?

Thanks!

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3 Answers 3

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10.04 does use 2.6.32 and 10.10 uses 2.6.35. You can install different versions than those on either Ubuntu release, or some other version. Applications generally do not know or care what kernel you are using. If you install the application, it goes on your disk, and is there no matter which kernel you boot.

The general rule is that you need one kernel, but when upgrading, you want to keep the previous version around in case the new version has problems, you can fall back. You can remove older versions so they do not pile up over time and add clutter.

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Thanks! I didn't install 10.04 but just 10.10 and then I have two versions of kernels. When running the two kernels, are they both 10.10 or one is 10.04 and the other is 10.10? –  Tim Feb 13 '11 at 2:21
    
@Tim: if they are both 2.6.35-smoething then they are probably from 10.10. From time to time they release an update so after a while you can get several versions that just have a different number after the "-". You can remove older ones with the package manager. –  psusi Feb 13 '11 at 16:30
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You can think of the kernel as just another program on your computer. The particular version you choose doesn't affect which other programs are installed.

Generally, newer versions of the kernel provide increased system stability and better hardware support. As they become available they are used in Ubuntu, but they are not strictly associated with any particular Ubuntu release. The kernel is developed separately from Ubuntu, and each Ubuntu release is likely to receive several kernel upgrades over its lifetime.

Ubuntu only runs one kernel at a time, so in an ideal world we should be able to install newer kernels just as we install newer applications — in place of the old version, leaving only one copy installed at a time. Since the kernel is vital to the system's ability to boot, however, it receives special treatment. Older versions are kept around as backups in case a newer version doesn't work. You should never have to use them, but, hypothetically, if one day Ubuntu doesn't boot after an upgrade, you might be able to recover by selecting an older kernel.

It doesn't hurt to leave older kernels installed, so unless you're running out of disk space there's not really any reason to remove them.

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Thanks! I was wondering what distinguish different releases of Ubuntu or different OSes, if they can use the same kernel? –  Tim Feb 13 '11 at 15:23
    
@Tim: all of the other programs that are installed, and how they are configured. Two distributions can even ship the same version of the kernel, but with different configurations. Distributions also usually have different patches they apply. –  psusi Feb 13 '11 at 16:32
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At some point, new OS releases will not work properly with older kernels.

What I want to say is: I think it is not possible to run an Ubuntu 10.10 on an, say, 8.04 kernel or earlier kernel (at least not without tweaking that requires in-depth understanding of the booting process).

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