On Tue, Jun 25, 2019 at 09:30:59AM -0400, Michael Stone wrote: > On Tue, Jun 25, 2019 at 09:05:30AM -0400, Greg Wooledge wrote: > > Debian's defaults are a bit baffling sometimes. They assumed a mobile > > device when they decided to put "allow-hotplug" on your wired ethernet > > interfaces, which breaks everything under the sun on traditional > > servers or workstations in a work environment. > > How? If the interface is in the system then allow-hotplug and auto are > synonyms. I have not observed the breakage in hundreds of servers.
With the default "allow-hotplug eth0" (or whatever interface name) setting, the NFS server will typically come up before DNS lookups are possible. When the NFS server starts up, it attempts to look up all of the client hostnames in /etc/exports. This is the *one* and *only* time the NFS server will perform this lookup. If the lookups fail at this time, the NFS server will not share anything with anyone, ever. (Until you notice the problem, and manually restart the NFS server. A mere exportfs -a will not suffice. It has to be a full restart.) NIS has similar issues. If ypbind can't contact its NIS server when you try to start it, well, that's just too bad. ypbind gives up and dies, and it is not respawned. I hope you weren't planning to login to that machine with an NIS account. I did say *traditional*. I know all you young kiddies are saying "but but but but nobody uses NIS or NFS any more, it's like, so OLD, bro, it's from like a previous DECADE". Well, they're still in use. This I promise you. And allow-hotplug breaks them. A lot. (I'm sure there are other services that break when allow-hotplug prevents them from doing name lookups or whatever at boot time, but these are the two big ones for me.)
