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Sysadmin Centos 7 with Kernel 4

Discussion in 'System Administration' started by nfn, Sep 10, 2016.

  1. nfn

    nfn New Member

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    Hi

    Do you run kernel 4 with Centos 7?
    Will we get any advantages by doing so?

    I'm using elrepo kernel 4 in a test vps without issues and some say we get a bette IO performance.

    What do you think?
     
  2. bassie

    bassie Active Member

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    Tested the ELrepo and Oracle kernel 4.* before but i can't recommend it for a production environment.
    The performance improvement is minimal (assuming a vps platform) but the stability a lot less.
    Cent(erprise)OS is all about business and stability and then performance, not the other way around.
     
  3. eva2000

    eva2000 Administrator Staff Member

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    FYI, Linode.com by default uses custom built 4.6+ Linux kernels on their VPSes. These are truly tested by Linode. This forum on Linode does as well :) There's plenty of performance improvements especially at TCP level some enabled by default.

    ELrepo mainline 4.x kernels you can try but as @bassie stated stability and buggy issues maybe introduced that you'd need to look after yourself.
     
  4. bassie

    bassie Active Member

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    Used Linode's default kernel before on web servers but websites aren't faster with it.
    There is to much code change in between different kernels, which follow each month.

    CentOS 7's default kernel is 3 years old and tested and tested it to the bee bone.
    Nothing changes just unless it is improvement in terms of stability, security or enhancement.

    If you earn with your web servers. For example, because your corporate website is on it. Always use CentOS's default. That's my advice. Stability over speed.
     
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  5. eva2000

    eva2000 Administrator Staff Member

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    I've used Linode custom 4.x kernels for 2 years now, no probs - probably because Linode tests them to be sure they work with their respective server hardware. But ELrepo haven't really tried as you say default CentOS 7 kernels pretty solid on 3.10. The performance comment was more with CentOS 6 2.6.32 in comparison to Linux 4.x as that's what I had on my mind :) The import TCP changes where made in CentOS 7 3.10 kernels anyway :)

    It's reason why before CentOS 7 was released, I was so interested in Oracle Linux's UEK 3.8 kernels as it offered something not available in CentOS 2.6.x at the time. Once, CentOS 7 was released with 3.10 kernels, that was no longer the case :D
     
  6. bassie

    bassie Active Member

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    If kernel 4.* is preferred, i recommend to use Oracle's UEK Release 4 kernel for EL6 or EL7.
    The kernel version in UEK Release 4 (UEK R4) is based on the mainline Linux kernel version 4.1.12.
    It is freely available via Oracle's RPM repo.

    On the one hand a relatively modern kernel.
    On the other hand still reasonable stability and minimal code changes.
     
    Last edited: Sep 11, 2016
  7. eva2000

    eva2000 Administrator Staff Member

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    Last edited: Sep 11, 2016
  8. eva2000

    eva2000 Administrator Staff Member

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    @bassie maybe you can clarify instructions at 3.3 Enabling Access to Public Yum Channels
    is the example they posted slightly incorrect if you only want UEKR4 you shouldn't need to enable [ol7_latest] ?

    So disable [ol7_latest] and enable only [ol7_UEKR4] ?
    Code (Text):
    [ol7_latest]
    name=Oracle Linux $releasever Latest ($basearch)
    baseurl=http://public-yum.oracle.com/repo/OracleLinux/OL7/latest/$basearch/
    gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-oracle
    gpgcheck=1
    enabled=0
    
    [ol7_UEK_latest]
    name=Latest Unbreakable Enterprise Kernel for Oracle Linux $releasever ($basearch)
    baseurl=http://public-yum.oracle.com/repo/OracleLinux/OL7/UEK/latest/$basearch/
    gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-oracle
    gpgcheck=1
    enabled=0
    
    [ol7_UEKR4]
    name=Latest Unbreakable Enterprise Kernel Release 4 for Oracle Linux $releasever ($basearch)
    baseurl=http://public-yum.oracle.com/repo/OracleLinux/OL7/UEKR4/latest/$basearch/
    gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-oracle
    gpgcheck=1
    enabled=1
    
    [ol7_UEKR4_OFED]
    name=OFED supporting tool packages for Unbreakable Enterprise Kernel on Oracle Linux 7 ($basearch)
    baseurl=http://public-yum.oracle.com/repo/OracleLinux/OL7/UEKR4_OFED/$basearch/
    gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-oracle
    gpgcheck=1
    enabled=0


    Chapter 1 New Features and Changes

     
  9. Sunka

    Sunka Active Member

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    Code:
    # uname -r
    3.10.0-327.36.1.el7.x86_64
    4.7 is lasted kernel I think.
    Would it be wise and safe to update to that kernel or stay on 3.10.0-327.36.1.el7.x86_64?
     
  10. eva2000

    eva2000 Administrator Staff Member

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    stick with default unless you know what you're doing :)
     
  11. Sunka

    Sunka Active Member

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    I do not know what I am doing, so long live the king Linux III.X. :)
     
  12. bassie

    bassie Active Member

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    What is the purpose of the server on which you want to change the kernel?
     
  13. Sunka

    Sunka Active Member

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