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Bug#895404: nfs-kernel-server: NFS server stops accepting mount request / mounted NFS directories became inaccecible on client

Started bysuperuser <kk@tatar.ru>
First post2018-04-11 10:10 +0200
Last post2018-04-12 21:10 +0200
Articles 2 — 2 participants

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  Bug#895404: nfs-kernel-server: NFS server stops accepting mount request / mounted NFS directories became inaccecible on client superuser <kk@tatar.ru> - 2018-04-11 10:10 +0200
    Bug#895404: NFS server stops accepting mount request / mounted NFS directories became inaccessible on client Sergio Gelato <Sergio.Gelato@astro.su.se> - 2018-04-12 21:10 +0200

#60670 — Bug#895404: nfs-kernel-server: NFS server stops accepting mount request / mounted NFS directories became inaccecible on client

Fromsuperuser <kk@tatar.ru>
Date2018-04-11 10:10 +0200
SubjectBug#895404: nfs-kernel-server: NFS server stops accepting mount request / mounted NFS directories became inaccecible on client
Message-ID<vDiZj-2Kg-3@gated-at.bofh.it>
Package: nfs-kernel-server
Version: 1:1.3.4-2.1
Severity: critical
Justification: causes serious data loss

Dear Maintainer,

NFS directory exported for local network host, and mounted by client.
After few days normal workload that share on client side became
inaccessible.
syslog on client side shows:  nfs: server <server_ip> not responding,
still trying
Tried to mount that share from NFS-server itself but it hangs for
timeout value(5 min) and report about that:
$ mount.nfs: Connection timed out

Tried to restart nfs-kernel-server.service but it is not gives any
positive result. Tried to kill nfsd processed by -9 and PID but it does
not kills any of them. journalctl show nothing suspicious.
Problem get resolved only after reboot of the server each time.

Changing kernel to one from backport repository did not helped.


-- Package-specific info:
-- rpcinfo --
   program vers proto   port  service
    100000    4   tcp    111  portmapper
    100000    3   tcp    111  portmapper
    100000    2   tcp    111  portmapper
    100000    4   udp    111  portmapper
    100000    3   udp    111  portmapper
    100000    2   udp    111  portmapper
    100005    1   udp  42805  mountd
    100005    1   tcp  42241  mountd
    100005    2   udp  44844  mountd
    100005    2   tcp  51819  mountd
    100005    3   udp  52308  mountd
    100005    3   tcp  54731  mountd
    100003    3   tcp   2049  nfs
    100227    3   tcp   2049
    100003    3   udp   2049  nfs
    100227    3   udp   2049
    100021    1   udp  46342  nlockmgr
    100021    3   udp  46342  nlockmgr
    100021    4   udp  46342  nlockmgr
    100021    1   tcp  41403  nlockmgr
    100021    3   tcp  41403  nlockmgr
    100021    4   tcp  41403  nlockmgr
-- /etc/default/nfs-kernel-server --
RPCNFSDCOUNT=8
RPCNFSDPRIORITY=0
RPCMOUNTDOPTS="--manage-gids --no-nfs-version 4"
RPCNFSDOPTS="--no-nfs-version 4"
NEED_SVCGSSD=""
RPCSVCGSSDOPTS=""
-- /etc/exports --
/srv/backups       10.196.1.224/27(rw,sync,no_subtree_check)
-- /proc/fs/nfs/exports --
# Version 1.1
# Path Client(Flags) # IPs

-- System Information:
Debian Release: 9.4
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.0-6-amd64 (SMP w/4 CPU cores)
Locale: LANG=ru_RU.UTF-8, LC_CTYPE=ru_RU.UTF-8 (charmap=UTF-8), LANGUAGE=ru_RU.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages nfs-kernel-server depends on:
ii  init-system-helpers  1.48
ii  keyutils             1.5.9-9
ii  libblkid1            2.29.2-1+deb9u1
ii  libc6                2.24-11+deb9u3
ii  libcap2              1:2.25-1
ii  libsqlite3-0         3.16.2-5+deb9u1
ii  libtirpc1            0.2.5-1.2
ii  libwrap0             7.6.q-26
ii  lsb-base             9.20161125
ii  netbase              5.4
ii  nfs-common           1:1.3.4-2.1
ii  ucf                  3.0036

nfs-kernel-server recommends no packages.

nfs-kernel-server suggests no packages.

-- no debconf information

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#60677 — Bug#895404: NFS server stops accepting mount request / mounted NFS directories became inaccessible on client

FromSergio Gelato <Sergio.Gelato@astro.su.se>
Date2018-04-12 21:10 +0200
SubjectBug#895404: NFS server stops accepting mount request / mounted NFS directories became inaccessible on client
Message-ID<vDPLA-SI-9@gated-at.bofh.it>
In reply to#60670
control: severity -1 normal
control: tags -1 + moreinfo

Dear reporter,

I'm sorry to hear that you have lost data. However, it doesn't seem very
constructive to make a bug release-critical without providing enough detail
to make a fix possible. NFS is a complex network protocol, and the root cause
of unexpected behaviour isn't always obvious at first glance.

First of all, has this bug been filed against the right package? The nfsd
processes are actually kernel threads (that's one reason "kill -9" doesn't
work on them), the corresponding package is the kernel image.

How many clients are accessing that NFS server when the problem occurs?
I see that you have RPCNFSDCOUNT=8 but the address range for allowed
clients is a /27. If you have 30 clients all trying to write at the same
time, some of them are going to have to wait until a server thread becomes
available. "server not responding, still trying" is a common symptom of
this. Have you tried tuning the server? You can adjust the thread count
without a reboot.

I don't see sec=krb5p in your /etc/exports, so NFS traffic on the wire
is probably unencrypted. Have you looked at it with tcpdump or a similar
tool, particularly when the problem occurs? For example it would be nice
to know whether that "Connection timed out" you get from mount.nfs is for
the portmapper (unlikely), for mountd, or for nfsd itself. (strace may
also tell you some of this.)

Are you familiar with rpcdebug? If client traffic is coming in but the
server isn't replying, you could set debugging flags and look at kernel
log output.

Other available debugging tools include the kernel's event tracing
subsystem, as well as nfsstat, nfsiostat and mountstats from package
nfs-common. (The last two are client-side, so maybe not so useful
if your problem really is at the server end.)

I can't help you much more than this: my own environment is NFSv4-only
(and I feel no urge to look back) while yours is anything but. But if
you manage to pinpoint more precisely what's wrong, someone else may
be able to provide better hints (or you may figure it out yourself).

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