Sorry if this is a duplicate. This time with correct email address... February 19, 2025 10:40 PM, "Rick Macklem" <rick.mack...@gmail.com> wrote:
> Hi, > > The subject line basically describes the problem glebius@ > ran into. When doing an NFS mount in /etc/fstab, it failed > since the DNS service was not yet working and, as such, > the DNS lookup of the server fqdn failed, causing the mount > to fail. Note that this behaviour has existed for decades. > > He feels this is a bug and that mount_nfs(8) should retry > getaddrinfo(3) calls until success, instead of failing the > mount when the first attempt fails. > The problem with just retrying getaddrinfo(3) is that it > could retry forever for simple failures like a typo in the > server fqdn. > I can see several ways this can be handled and would > like feedback from others w.r.t. these alternatives. > > 1) Simply document this case and encourage use of > host names in /etc/hosts for NFS servers along with > specifying use of file before dns in nsswitch.conf. > Doing this results in the mounts working whether or > not DNS is working. > > 2) Call it a bug and patch mount_nfs(8) to retry getaddrinfo(3) > until it succeeds. (I feel this would be a POLA violation, > given that the current behaviour has existed for decades > and for simple cases where the fqdn will never resolve > the behaviour would be to hang at the mount attempt > during boot unless "bg" is specified for the /etc/fstab entry.) > > 3) Add a new NFS mount option "retrydns=<N>", which would enable > retries of getaddrinfo(3). This would avoid any POLA violation and > would allow for a convenient way to document the behaviour in > "man mount_nfs". > > 4) ??? > > So, what do you think is the preferred change? IMHO Not A Bug. This is the expected behavior -- if a dependent service is not up/complete, then return failure. This has always held true for services dependent on name resolution. Start DNS early, or dependent services late. For domains/hosts you control it might be prudent to manage hosts(5). In any case, maybe your best option is document the appropriate man pages. I can't speak to to your software features. But maybe adding a delay, or retry attempts may seem a good choice of Feature to you. But IMHO the reported error is pilot error. Anyone running NFS should already know how to remedy the situation, or be directed to the appropriate man pages. --Chris > > rick > ps: I looked and the return value from getaddrinfo(3) does not > appear to be useful to discern the case of "DNS service not > running yet". (I think it replies EAI_FAIL for this case.)
