ntp running in chroot stopped working after Debian Stretch upgrade

Today I upgraded my root server from Jessie to Stretch, and suddenly ntp stopped working.

I found errors like follows in the log, which were obviously due to failures in name resolution:

2018-05-31T07:44:48.900756+00:00 myhost ntpd[22855]: giving up resolving host 1.debian.pool.ntp.org: Servname not supported for ai_socktype (-8)

The solution to make this work was to bind-mount some files and directories essential for name resolution into the chroot jail.

First create some directories and some dummy files:

# mkdir /var/lib/ntp/etc /var/lib/ntp/lib /var/lib/ntp/proc
# mkdir /var/lib/ntp/usr /var/lib/ntp/usr/lib
# touch /var/lib/ntp/etc/resolv.conf /var/lib/ntp/etc/services

Then update your /etc/fstab as follows:

...
#ntpd chroot mounts
/etc/resolv.conf  /var/lib/ntp/etc/resolv.conf none bind 0 0
/etc/services	  /var/lib/ntp/etc/services none bind 0 0
/lib		  /var/lib/ntp/lib none bind 0 0
/usr/lib	  /var/lib/ntp/usr/lib none bind 0 0
/proc		  /var/lib/ntp/proc none bind 0 0

Finally mount all these binds:

# mount -a

Thanks to the ArchLinux guys where I found this.

To check whether your ntp is working again, you can use the following command which shows a list of peers known to your ntp server:

# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 0.debian.pool.n .POOL.          16 p    -   64    0    0.000    0.000   0.000
 1.debian.pool.n .POOL.          16 p    -   64    0    0.000    0.000   0.000
 2.debian.pool.n .POOL.          16 p    -   64    0    0.000    0.000   0.000
 3.debian.pool.n .POOL.          16 p    -   64    0    0.000    0.000   0.000
*ptbtime1.ptb.de .PTB.            1 u   46   64  377   11.483   -0.411   0.201
+ptbtime2.ptb.de .PTB.            1 u   52   64  377   11.502   -0.533   1.069
+ptbtime3.ptb.de .PTB.            1 u   47   64  377   11.451   -0.510   3.866
#batleth.sapient 131.188.3.221    2 u   44   64  377    0.188    1.097   0.176
#5.199.135.170 ( 130.149.17.21    2 u   45   64  377   11.271    0.581   0.396
-mail.morbitzer. 193.175.73.151   2 u   47   64  377    2.760    0.556   0.278
#hotel.zq1.de    161.62.157.173   3 u   46   64  377    0.094    1.384   0.261
-ntp2.m-online.n 212.18.1.106     2 u   47   64  377    7.167   -0.333   0.190
#2a03:b0c0:3:d0: 81.94.123.16     3 u   49   64  377    6.288   -2.071   1.760
#touka.thehomeof 130.149.17.21    2 u   48   64  377    0.206    0.932   0.222
+maggo.info      124.216.164.14   2 u   42   64  377    0.278   -0.137   0.436
+weyoun4.cord.de 124.216.164.14   2 u   44   64  377    2.849   -0.255   0.409
+opnsense.sauff. 222.217.153.8    2 u   43   64  377    0.270   -0.617   0.167
-web1.sys.ccs-ba 192.53.103.104   2 u   35   64  377    0.173   -1.251   0.220
#uruz.org        122.227.206.195  3 u   49   64  377    0.216    1.694   0.309
#clients5.arcani 162.23.41.55     2 u   38   64  377    6.120   -1.500   0.130
+stratum2-1.NTP. 129.70.130.71    2 u   47   64  377   14.043    1.625   0.394

The following command confirms that your current time is actually correct (within certain limits, of course):

# ntpstat
synchronised to NTP server (192.53.103.108) at stratum 2
   time correct to within 15 ms
   polling server every 64 s

If this was helpful, I would be happy to hear from you.

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