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Thread: Why is Ubuntu constantly rewriting my /etc/hosts file?

  1. #1
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    Why is Ubuntu constantly rewriting my /etc/hosts file?

    Ubuntu Users,

    On my main desktop machine I run a LAMP server that is not connected to the internet, it's just for testing web sites locally.

    Since upgrading to Ubuntu 10.10, my /etc/hosts on my local testing
    machine keeps getting wiped out.

    After the first time I noticed it happening, I thought, "okay, fine, must have been over written during the upgrade". So I put back in what I had before.

    Then later, my local web sites weren't working again, and it turned out
    my /etc/hosts got wiped out again. Maybe after a boot.

    So it looks like when Apache starts up, it generates /etc/hosts, or
    something, and I need to put my list of domains in some other file... or
    something.

    I figured I'd go to the Apache web site to see what's up, but it seems like this isn't something Apache does.

    My local LUG has suggested that this behaviour is particular to Ubuntu and it's network management "features".

    Does anyone know if this is something Ubuntu is doing?

    And in any case, does anyone know how I get my /etc/hosts file to not be rewritten every time Apache starts?

    Thank you for any advice.
    Desktop: Ubuntu 12.04 Gnome Classic, Intel i5, 4GB RAM, Nvidia GeForce 9600, dual monitor
    Laptop: Ubuntu 12.04 Gnome Classic (no effects), Panasonic Let's Note CF-Y2 laptop, 1GB RAM
    Media Server: Mythbuntu 12.04, Intel Q4, 4GB RAM

  2. #2
    Join Date
    May 2008
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    Ubuntu

    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    I had a similar problem with a different cause, but to make a long story short, I changed the permissions on the /etc/hosts file to read only. If you don't know how to do this, run the command:

    Code:
    sudo chmod 444 /etc/hosts
    To restore the write permissions, run the command:

    Code:
    sudo chmod 644 /etc/hosts

  3. #3
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    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    Quote Originally Posted by Dave M G View Post
    ... network management "features".
    The means that you are not supposed to edit the file yourself. You have to use the network manager or some other file/software to make your settings. I am not sure which or where.

  4. #4
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    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    Quote Originally Posted by 3Miro View Post
    The means that you are not supposed to edit the file yourself. You have to use the network manager or some other file/software to make your settings. I am not sure which or where.
    This is not true for the hosts file. I use custom entries in the hosts file and I use Network Manager on many different machines and I've never had a problem. There are some files related to networking that you should not edit, but hosts isn't one of them.

  5. #5
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    Xubuntu 14.04 Trusty Tahr

    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    You might try killing the avahi-daemon process. Or uninstalling it completely - I have never found anything useful it does, but have found that it sometimes does things I don't want. It makes every incoming connection take several seconds to complete, rendering the PC useless as a web server, for instance. Very microsoft-like.

  6. #6
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    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    Thanks to everyone for responding.

    While I could change the permissions or use chattr to prevent the /etc/hosts from being altered, I'd rather know what is actually going on.

    Is there no one who can say for sure what exactly is happening?

    Or at least confirm if it is in fact some Ubuntu "feature" that is responsible for this, and not some other bug? I have two computers on which this is happening, but there is always the chance I have got some setting wrong.

    I looked up avahi-daemon, but I have not yet found any specific mention of it altering /etc/hosts.
    Desktop: Ubuntu 12.04 Gnome Classic, Intel i5, 4GB RAM, Nvidia GeForce 9600, dual monitor
    Laptop: Ubuntu 12.04 Gnome Classic (no effects), Panasonic Let's Note CF-Y2 laptop, 1GB RAM
    Media Server: Mythbuntu 12.04, Intel Q4, 4GB RAM

  7. #7
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    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    Hi, I've the same problem, and I can confirm that it is a "feature" of the last Ubuntu Maverick because until last week everything worked as expected.

    I don't know if it is something related to apache rewriting the file (why should apache do this??) or, probably, something someone put somewhere in ubuntu (why should someone do this?!?).

    It's very annoying, a linux system should NOT do something itself, it's the basic difference between linux and windows, why can't I modify my damn host file?

    I'll start doing a research about this behaviour.

    edit: just an update, it seems that this is the only thread referring to this problem on the internet. In my hosts file I read "#Added by Network Manager" after my ip-address and my hostname. I get an IP from a DHCP server, so probably Network Manager decides to update hosts file with my ip address, and then it removes my modification by resetting the file to its "copy": it's not an empty host file, but simply the version that it found the first boot after the dist-upgrade (because I modify frequently hosts file as I'm a web programmer, and my hosts file was already customised). I will open a ticket on launchpad.
    Last edited by emas80; October 18th, 2010 at 11:42 AM. Reason: new data retrieved

  8. #8
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    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    Looks like it's network-manager that's responsible.

    I was able to reproduce the problem by editing /etc/hosts (and removing the '::1 localhost6.localdomain localhost6' line) and then restarting network-manager (sudo /etc/init.d/network-manager restart) When you check /etc/hosts you'll notice that the offending line is back.

    I've disabled ipv6 through /etc/sysctl.conf
    I've also checked all the interfaces in the network-manager GUI in Gnome to see if ipv6 was set to 'ignore' and they all are. Yet when you restart network-manager it still goes and adds ipv6 specific lines to /etc/hosts

    A bug perhaps?

  9. #9
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    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    Quote Originally Posted by crahan View Post
    Looks like it's network-manager that's responsible.

    I was able to reproduce the problem by editing /etc/hosts (and removing the '::1 localhost6.localdomain localhost6' line) and then restarting network-manager (sudo /etc/init.d/network-manager restart) When you check /etc/hosts you'll notice that the offending line is back.

    I've disabled ipv6 through /etc/sysctl.conf
    I've also checked all the interfaces in the network-manager GUI in Gnome to see if ipv6 was set to 'ignore' and they all are. Yet when you restart network-manager it still goes and adds ipv6 specific lines to /etc/hosts

    A bug perhaps?
    This does not happen in my 10.04 system with IPv6 set to "Ignore" in my Network Manager, nothing whatsoever happens to my hosts file when I restart it.

    Anyone using DHCP should realise that the DHCP server will always change the hosts file because of the data in the DHCP configuration packet.
    Regards, David.
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  10. #10
    Join Date
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    Re: Why is Ubuntu constantly rewriting my /etc/hosts file?

    I am using Ubuntu Maverick for 10 days now and the overwriting of the hosts file happened to me only twice, not after every reboot but I think after I changed the networks (connected to another wireless network).
    Strange behaviour indeed, I have to find a solution. I did not have this problem in any other Ubuntu previous version.

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