Xen users - Nov 2005 - Warning wrt starting the xen3.0 network-bridge from init scripts on Gentoo

Gentoo is rather aggressive wrt making sure that dependencies are fulfilled.

This means that running /etc/init.d/net.eth0 restart from an init script 
which declares that it requires a functioning network to work will, if 
no interfaces other than eth0 is configured, cause that init script to 
be told to shut down before the network adapter can be deconfigured!

So... if you''re going to call network-bridge or xend from an init
script
on Gentoo, and that init script declares that it has a dependency on 
having the network up, make sure you have another interface (I use 
dummy0) defined as UP, lest the point in network-bridge where it 
restarts the interface currently being configured result in a very 
confused state.

(I spent much too much time debugging this issue today).


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On Wednesday 02 November 2005 22:51, Charles Duffy
wrote:
> Gentoo is rather aggressive wrt making sure that dependencies are
> fulfilled.
>
> This means that running /etc/init.d/net.eth0 restart from an init script
> which declares that it requires a functioning network to work will, if
> no interfaces other than eth0 is configured, cause that init script to
> be told to shut down before the network adapter can be deconfigured!
>
> So... if you''re going to call network-bridge or xend from an init
script
> on Gentoo, and that init script declares that it has a dependency on
> having the network up, make sure you have another interface (I use
> dummy0) defined as UP, lest the point in network-bridge where it
> restarts the interface currently being configured result in a very
> confused state.
>
> (I spent much too much time debugging this issue today).
have a look at /etc/conf.d/rc:

# RC_NET_STRICT_CHECKING allows some flexibility with the
''net'' service.
# The following values are allowed:
#  none  - The ''net'' service is always considered up.
#  no    - This basically means that at least one net.* service besides net.lo
#          must be up.  This can be used by notebook users that have a wifi 
and
#          a static nic, and only wants one up at any given time to have the
#          ''net'' service seen as up.
#  lo    - This is the same as the ''no'' option, but net.lo is
also counted.
#          This should be useful to people that do not care about any specific
#          interface being up at boot.
#  yes   - For this ALL network interfaces MUST be up for the
''net'' service to
#          be considered up.

RC_NET_STRICT_CHECKING="lo"

and, bingo, you can play with your xen bridges without all net-dependend 
services going down...

/Ernst

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> Gentoo is rather aggressive wrt making sure that dependencies 
> are fulfilled.
> 
> This means that running /etc/init.d/net.eth0 restart from an 
> init script which declares that it requires a functioning 
> network to work will, if no interfaces other than eth0 is 
> configured, cause that init script to be told to shut down 
> before the network adapter can be deconfigured!
Hilarious! 
 
> So... if you''re going to call network-bridge or xend from an 
> init script on Gentoo, and that init script declares that it 
> has a dependency on having the network up, make sure you have 
> another interface (I use
> dummy0) defined as UP, lest the point in network-bridge where 
> it restarts the interface currently being configured result 
> in a very confused state.
creating a dummy interface is gross. Is there no other way to bypass
this? it would be good to make sure our scripts worked on gentoo, but
there''s a limit to the amount of ugliness that''s endurable. We
could
have distro specific scripts, but this isn''t quite yet justified...

Ian

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Ian Pratt wrote the following on 04.11.2005 17:12 :
>>Gentoo is rather aggressive wrt making sure that dependencies 
>>are fulfilled.
>>
>>This means that running /etc/init.d/net.eth0 restart from an 
>>init script which declares that it requires a functioning 
>>network to work will, if no interfaces other than eth0 is 
>>configured, cause that init script to be told to shut down 
>>before the network adapter can be deconfigured!
>>    
>>
>
>Hilarious!
>  
>
In fact this isn''t a problem at all. A Gentoo admin only have to set:
RC_NET_STRICT_CHECKING="lo"
in /etc/conf.d/rc

the config file states:
# RC_NET_STRICT_CHECKING allows some flexibility with the
''net'' service.
# The following values are allowed:
#  none  - The ''net'' service is always considered up.
#  no    - This basically means that at least one net.* service besides 
net.lo
#          must be up.  This can be used by notebook users that have a 
wifi and
#          a static nic, and only wants one up at any given time to have the
#          ''net'' service seen as up.
#  lo    - This is the same as the ''no'' option, but net.lo is
also counted.
#          This should be useful to people that do not care about any 
specific
#          interface being up at boot.
#  yes   - For this ALL network interfaces MUST be up for the
''net''
service to
#          be considered up.

Gentoo scripts are far more flexible than you would believe at first 
glance :-) Just look at the /etc/conf.d/<subsystem>. In this case we are 
speaking of the "rc" script which does the dependency resolution.

Lionel.

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