Re: Odd behavior from amd

[christos%astron.com@localhost (Christos Zoulas)]

In article <200802082042.m18KgVxR003362%mcci.com@localhost>,
Lars Friend  <lfriend%mcci.com@localhost> wrote:
>
>Hello all,
>
>       I've got a strange problem that has been plaguing me for a while, 
>and I have spent a good portion of today trying to get to the bottom of.
>
>       We have a cluster of several machines (NetBSD 3.1 i386 running 
>release 3.1 GENERIC kernels), each performing different functions, 
>and we have our home directories mounted via nfs (exported split 
>between a couple of the servers) by running amd with the same maps on 
>each server.  This allows a user to log in anywhere and have their 
>same home directory no matter which machine they are on.  This is 
>generally very handy, and it works with remarkable stability, until I 
>go and move a [not logged in] user's home directory from one server 
>to another (for disk space management reasons, for instance).
>
>       The problem boils down to this:  Every once in a while when I update 
>the amd maps, amd will catch the change quickly enough, and amq will 
>reflect the correct change, but the directory where the symlinks live 
>(which amd implements as a read-only local NFS system which we mount 
>on /home) will still have a symlink pointing to the old mapping location.
>
>       For instance, if I have server_a, server_b, and server_c, and 
>server_d where the home directories are mapped like this (on all four hosts):
>
>bob    host!=server_a;rhost:=server_a;rfs:=/data/export/home \
>       host==server_a;fs:=/data/export/home;type:=link
>joe    host!=server_b;rhost:=server_b;rfs:=/data/export/home \
>       host==server_b;fs:=/data/export/home;type:=link
>dave   host!=server_b;rhost:=server_b;rfs:=/data/export/home \
>       host==server_b;fs:=/data/export/home;type:=link
>
>and I change that map to: (after copying joe's home directory from 
>server b to server a)
>
>bob    host!=server_a;rhost:=server_a;rfs:=/data/export/home \
>       host==server_a;fs:=/data/export/home;type:=link
>joe    host!=server_a;rhost:=server_a;rfs:=/data/export/home \
>       host==server_a;fs:=/data/export/home;type:=link
>dave   host!=server_b;rhost:=server_b;rfs:=/data/export/home \
>       host==server_b;fs:=/data/export/home;type:=link
>
>After waiting for the map_reload_interval to expire, all four servers 
>(a,b,c,d) will (when asked with amq) tell me that the mapping has 
>been picked up and honored, but if I go and look in /home, sometimes 
>(but not always), the old symlink will still be there:
>
>lrwxrwxrwx  1 root  wheel  21 Feb  8 15:33 /home/joe -> 
>/.automount/server_b/data/export/home/joe
>
>       This seems to occur more on servers that have lots of activity in 
>the other amd mapped home directories, but not reliably on any given 
>host.  An amq -f will not clear this condition, and it seems that the 
>only way to get rid of this is to stop and restart amd (which I 
>obviously don't like to do with 50+ users logged in).
>
>Does anybody have any suggestions?

Use 'amq -u' to unmount the offending partition before 'amq -f'.

christos