[CentOS] Two small issues after upgrade to 4.2

[Scot L. Harris]

On Mon, 2005-10-24 at 08:40, Kai Schaetzl wrote:
> I made a yum update to 4.2 yesterday. The first "major" update I did on 
> CentOS, I'm only using it for a few weeks now, starting with 4.1. Mainly 
> for evaluation for a prospected migration from Suse to CentOS. Basically 
> the update went very well, fast (only 180 MB needed to be installed) and 
> smooth. But there were two small issues where I don't know why they 
> happened:

> 2. sshd seems to start twice or so since that update. No problems with 
> ssh, though.
> 
> from boot.log:
> Oct 24 14:00:16 nx05 sshd:  succeeded
> 
> from warn log:
> Oct 24 14:00:16 nx05 sshd[1737]: error: Bind to port 22 on 0.0.0.0 failed: 
> Address already in use.
> 
> Same thing happens when I restart sshd and even when I reload it.
> There was a new sshd_config installed, I think I read something about 
> removing ssh 1 protocol from it. This can't be the cause. There's only one 
> instance of sshd running apart from the children for actual logins.
> Why is this happening, how to fix it?
> 

Most of the times I have seen this it is caused due to having IPv6
enabled.  ssh binds to the port on IPv4 address or IPv6 then tries to
bind a second time to the same port.

Personally I usually disable IPv6 and the zero conf stuff on systems. 
Have not had a use for either of these on systems and I suspect the zero
conf stuff could lead to security issues if/when someone studies it a
little more.  :)

> There is another question that arises in this context: will a yum update 
> always overwrite with new configuration files, if that file got changed 
> from the originally installed one? I'm used from Suse that new 
> configuration files get saved with another extension if the original file 
> got changed or in some cases it overwrites the file but copies the old 
> file to a backup. I can also expressly exclude some config files from 
> overwriting via sysconfig (if I remember correctly), can I do similar with 
> CentOS?

Many rpm packages will typically not over write configuration files that
have been modified.  They will create a .rpmnew file for the config
file.  But don't count on that action.  Backups are good to have of any
configuration files you have changed.