aSteve's questions

I have a Postfix mail server, running on a host with multiple network adapters, one of which is a virtual tun0 device. I need this mail server to accept connections on any adapter - and send email only on the virtual tun device.

I have a configuration, in line with the answer to this question, which defines smtp_bind_address=10.20.30.40 - where 10.20.30.40 is the address associated with the tun0 device. This server server doesn't support IPV6.

For years, this appeared to work perfectly - until, one day, the tun0 device died - and Postfix sent email over the default network device, eth0 (10.0.0,1) not tun0.

Is this expected behaviour? Are there settings I can change to ensure that Postfix only ever dispatches email over tun0 (10.20.30.40) - leaving messages in the queue if tun0 is not available?

In case it is relevant, this is on Ubuntu 16.04.2 LTS with Postfix version 3.1.0-3. tun0 is implemented using OpenVPN version 2.3.10-1ubuntu2.1

-- Edit to add extra details --

$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.1        0.0.0.0         UG    0      0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     0      0        0 eth0
10.20.30.40     0.0.0.0         255.255.255.255 UH    0      0        0 tun0

This server runs several services - of which Postfix is only one. Only email needs to be routed over 10.20.30.40 - all the other services need to be routed over the default gateway.

I am aware that there are various protocols by which MS Exchange exposes access to services - including:

• EAS : Exchange Active Sync - A proprietary protocol that appears to be the default option for access to Exchange from mobile devices.
• EWS : Exchange Web Services - An openly documented SOAP protocol- a standard Web Service with a WSDL definition.
• Exchange Outlook Anywhere (also known as RPC/HTTP) ...now deprecated in favour of MAPI over HTTP?

If I only have access to Exchange Web Services, for a particular Exchange Server, is there any way to access those services using Outlook Mobile (on Android, iOS or Win-10-phone)?

If direct access is not viable, is there such a thing as an Exchange-Active-Sync (client-side) to Exchange-Web-Services (server-side) bridge?

If no bridge between EAS and EWS exists, is it feasible to deploy Outlook Web App to present EWS services in web browsers on phones? (Essentially, can Outlook Web App be configured to, exclusively, communicate with Exchange using EWS via a Web Proxy?)

If none of the above are feasible, can I use Outlook (on a Windows laptop) to connect to the EWS Service?

I've recently switched out a failed router... and, a while later, I discovered a lot (at least an order or magnitude more than the number of queries) of errors reported in /var/log/syslog - of the form:

Mar 18 19:53:20 kenneth named[4022]: DNS format error from 192.112.36.4#53 resolving ./NS: non-improving referral
Mar 18 19:53:20 kenneth named[4022]: error (FORMERR) resolving './NS/IN': 192.112.36.4#53

It might be relevant that I've got the following in bind.conf:

dnssec-enable no;
dnssec-validation no;

Is this likely an issue with the new router corrupting UDP datagrams, or something else? The new router is an (inexpensive) Netgear WNR854T - it has the latest firmware applied.

Can anyone suggest how best to diagnose this fault if it's not obvious from the above?

-- Additional details -- This is a typical response from dig for an address I'm sure should resolve.

$ dig A barclays.co.uk                                         ~

; <<>> DiG 9.8.1-P1 <<>> A barclays.co.uk
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22161
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;barclays.co.uk.                        IN      A

;; Query time: 84 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Wed Mar 20 23:08:40 2013
;; MSG SIZE  rcvd: 32
$

I have an internet connected Ubuntu server, connected by Ethernet to a residential ADSL line. This is adequate, most of the time, but I can't rely upon the ADSL link to be as reliable as I'd like. Murphy's law has already dictated that down-time comes when it is least convenient.

I'd like to use a 'pay-as-you-go' 3G USB dongle to provide a fail-over. I'm lacking information both about sample configurations that work for other people - and about the most suitable (inexpensive) hardware for my purposes. The objective is that, when my ADSL line is disconnected, the server detects this and dials up the 3G service - monitoring the ADSL line and switching back seamlessly when its connection is restored.

The principle service I care about is an OpenVPN tunnel - over UDP to a remote server. The other useful service would be Squid - so I'd still have web-access from my LAN when ADSL is disconnected.

Questions:

1. How difficult would this be to set up?
2. Would I be forced to 'roll my own' - or are there packages/howtos I've overlooked?
3. What (inexpensive) hardware is recommended (concerned with unattended reliability - mainly)?
4. Any anecdotes of success or failure from others who've tackled this already?

I bought a 1TB Seagate Barracuda 7200.12 - ST31000528AS drive about 18 months ago because it had a 5-year warranty, and used it alongside a Samsung Spinpoint under Ubuntu Server as one half of a software RAID-1 array.

Yesterday, smartd started reporting a problem:

Jan 18 06:08:03 svr smartd[2672]: Device: /dev/sdb [SAT], 2 Currently unreadable (pending) sectors
Jan 18 06:08:03 svr smartd[2672]: Device: /dev/sdb [SAT], 2 Offline uncorrectable sectors

I followed this up by investigations with smartctl... and, after scheduling some tests, I get these results:

$ smartctl -l error /dev/sdb
smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.0.0-14-generic] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF READ SMART DATA SECTION ===
SMART Error Log Version: 1
No Errors Logged
$ smartctl -l selftest /dev/sdb
smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.0.0-14-generic] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF READ SMART DATA SECTION ===
SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Extended offline    Completed: read failure       10%     12451         1953523918
# 2  Short offline       Completed: read failure       90%     12445         1953523918
# 3  Short offline       Completed: read failure       60%     12445         1953523918
# 4  Extended offline    Completed without error       00%      5532         -

$

Only the 'selftest' output documents any kind of a problem - though I'm not 100% clear how to interpret it. I suspect I may have scheduled two short tests at the same time... though I'm not sure why one has 90% remaining and the other 60%. Come to that, I can't see why my long test has 10% remaining.

Another curious thing is that Raid-1 hasn't detected any kind of problem (or, at least, that's what I understand "[2/2][UU]" means. While there are three partitions on sdb, only one is not trivially small... Of the other two, one is a boot partition (replicated between both drives for disaster recovery) and the other is swap.

$ cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb3[1] sda3[0]
      967843840 blocks [2/2] [UU]

unused devices: <none>

A few questions...

• Am I correct in thinking that this is strong evidence that sdb has a fault? Is it possible that this is a software not hardware issue?
• Can I get a list of all the blocks that are detected as faulty - and establish which partitions they're in?
• Can I (do I need to) map-out these bad sectors pending acquisition of a replacement drive?
• Are a lot of people experiencing this sort of problem with the 1TB Seagate Barracuda drives?
• Does anyone know if the output from smartmontools above is sufficient evidence of fault to secure a replacement under warranty?

Any advice/comments warmly appreciated... :)

As requested... smartctl --all /dev/sdb

smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.0.0-14-generic] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF INFORMATION SECTION ===
Model Family:     Seagate Barracuda 7200.12
Device Model:     ST31000528AS
Serial Number:    9VP5LFZA
LU WWN Device Id: 5 000c50 0200362a0
Firmware Version: CC38
User Capacity:    1,000,204,886,016 bytes [1.00 TB]
Sector Size:      512 bytes logical/physical
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   8
ATA Standard is:  ATA-8-ACS revision 4
Local Time is:    Thu Jan 19 18:54:01 2012 GMT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

General SMART Values:
Offline data collection status:  (0x82)     Offline data collection activity
                                    was completed without error.
                                    Auto Offline Data Collection: Enabled.
Self-test execution status:      ( 113)     The previous self-test completed having
                                    the read element of the test failed.
Total time to complete Offline
data collection:            (  609) seconds.
Offline data collection
capabilities:                        (0x7b) SMART execute Offline immediate.
                                    Auto Offline data collection on/off support.
                                    Suspend Offline collection upon new
                                    command.
                                    Offline surface scan supported.
                                    Self-test supported.
                                    Conveyance Self-test supported.
                                    Selective Self-test supported.
SMART capabilities:            (0x0003)     Saves SMART data before entering
                                    power-saving mode.
                                    Supports SMART auto save timer.
Error logging capability:        (0x01)     Error logging supported.
                                    General Purpose Logging supported.
Short self-test routine
recommended polling time:    (   1) minutes.
Extended self-test routine
recommended polling time:    ( 178) minutes.
Conveyance self-test routine
recommended polling time:    (   2) minutes.
SCT capabilities:          (0x103f) SCT Status supported.
                                    SCT Error Recovery Control supported.
                                    SCT Feature Control supported.
                                    SCT Data Table supported.

SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x000f   118   099   006    Pre-fail  Always       -       198953639
  3 Spin_Up_Time            0x0003   095   095   000    Pre-fail  Always       -       0
  4 Start_Stop_Count        0x0032   100   100   020    Old_age   Always       -       32
  5 Reallocated_Sector_Ct   0x0033   100   100   036    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x000f   076   060   030    Pre-fail  Always       -       45828174
  9 Power_On_Hours          0x0032   086   086   000    Old_age   Always       -       12498
 10 Spin_Retry_Count        0x0013   100   100   097    Pre-fail  Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   020    Old_age   Always       -       16
183 Runtime_Bad_Block       0x0032   100   100   000    Old_age   Always       -       0
184 End-to-End_Error        0x0032   100   100   099    Old_age   Always       -       0
187 Reported_Uncorrect      0x0032   100   100   000    Old_age   Always       -       0
188 Command_Timeout         0x0032   100   100   000    Old_age   Always       -       0
189 High_Fly_Writes         0x003a   100   100   000    Old_age   Always       -       0
190 Airflow_Temperature_Cel 0x0022   064   056   045    Old_age   Always       -       36 (Min/Max 25/44)
194 Temperature_Celsius     0x0022   036   044   000    Old_age   Always       -       36 (0 20 0 0)
195 Hardware_ECC_Recovered  0x001a   025   011   000    Old_age   Always       -       198953639
197 Current_Pending_Sector  0x0012   100   100   000    Old_age   Always       -       2
198 Offline_Uncorrectable   0x0010   100   100   000    Old_age   Offline      -       2
199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age   Always       -       0
240 Head_Flying_Hours       0x0000   100   253   000    Old_age   Offline      -       253776732631285
241 Total_LBAs_Written      0x0000   100   253   000    Old_age   Offline      -       2894995523
242 Total_LBAs_Read         0x0000   100   253   000    Old_age   Offline      -       2366564210

SMART Error Log Version: 1
No Errors Logged

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Extended offline    Completed: read failure       10%     12451         1953523918
# 2  Short offline       Completed: read failure       90%     12445         1953523918
# 3  Short offline       Completed: read failure       60%     12445         1953523918
# 4  Extended offline    Completed without error       00%      5532         -

SMART Selective self-test log data structure revision number 1
 SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
    1        0        0  Not_testing
    2        0        0  Not_testing
    3        0        0  Not_testing
    4        0        0  Not_testing
    5        0        0  Not_testing
Selective self-test flags (0x0):
  After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute delay.