systemd unit file starts Tor before IPv6 address is available
On Ubuntu xenial, systemd starts Tor before the IPv6 address is available and so Tor fails to assign an IPv6 address then exits. systemd tries to restart Tor (I think three times) but even by the last time there's still no IPv6 address assigned and hence Tor fails to start.
As a work-around I copied /lib/systemd/system/tor* to /etc/systemd/system/ and added RestartSec=10 to the [Service] section of tor@default.service and tor@.service. This slows down the restart such that by the second time tor starts, there is an IPv6 address available.
See log file below.
Feb 08 15:06:28 ephemer tor[1313]: Feb 08 15:06:28.587 [notice] Tor 0.3.3.1-alpha (git-dc340725f08717e3) running on Linux with Libevent 2.0.21-stable, OpenSSL 1.0.2g, Zlib 1.2.8, Liblzma 5.1
.0alpha, and Libzstd N/A.
Feb 08 15:06:28 ephemer tor[1313]: Feb 08 15:06:28.588 [notice] Tor can't help you if you use it wrong! Learn how to be safe at https://www.torproject.org/download/download#warning
Feb 08 15:06:28 ephemer tor[1313]: Feb 08 15:06:28.588 [notice] This version is not a stable Tor release. Expect more bugs than usual.
Feb 08 15:06:28 ephemer tor[1313]: Feb 08 15:06:28.588 [notice] Read configuration file "/usr/share/tor/tor-service-defaults-torrc".
Feb 08 15:06:28 ephemer tor[1313]: Feb 08 15:06:28.588 [notice] Read configuration file "/etc/tor/torrc".
Feb 08 15:06:28 ephemer tor[1313]: Feb 08 15:06:28.591 [notice] Based on detected system memory, MaxMemInQueues is set to 8192 MB. You can override this by setting MaxMemInQueues by hand.
Feb 08 15:06:28 ephemer tor[1313]: Configuration was valid
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.651 [notice] Tor 0.3.3.1-alpha (git-dc340725f08717e3) running on Linux with Libevent 2.0.21-stable, OpenSSL 1.0.2g, Zlib 1.2.8, Liblzma 5.1
.0alpha, and Libzstd N/A.
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.651 [notice] Tor can't help you if you use it wrong! Learn how to be safe at https://www.torproject.org/download/download#warning
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.651 [notice] This version is not a stable Tor release. Expect more bugs than usual.
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.651 [notice] Read configuration file "/usr/share/tor/tor-service-defaults-torrc".
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.651 [notice] Read configuration file "/etc/tor/torrc".
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Based on detected system memory, MaxMemInQueues is set to 8192 MB. You can override this by setting MaxMemInQueues by hand.
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Scheduler type KIST has been enabled.
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Opening Socks listener on 127.0.0.1:9050
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Opening OR listener on 0.0.0.0:9001
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Opening OR listener on [2001:630:212:2a8:a6bf:1ff:fe25:b961]:9001
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [warn] Could not bind to 2001:630:212:2a8:a6bf:1ff:fe25:b961:9001: Cannot assign requested address
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Opening Directory listener on 0.0.0.0:9030
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Closing partially-constructed Socks listener on 127.0.0.1:9050
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Closing partially-constructed OR listener on 0.0.0.0:9001
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [notice] Closing partially-constructed Directory listener on 0.0.0.0:9030
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [warn] Failed to parse/validate config: Failed to bind one of the listener ports.
Feb 08 15:06:28 ephemer tor[1352]: Feb 08 15:06:28.653 [err] Reading config failed--see warnings above.
Feb 08 15:06:28 ephemer systemd[1]: tor@default.service: Main process exited, code=exited, status=1/FAILURE
-- Subject: Unit tor@default.service has failed
-- Unit tor@default.service has failed.
Feb 08 15:06:28 ephemer systemd[1]: tor@default.service: Unit entered failed state.
Feb 08 15:06:28 ephemer systemd[1]: tor@default.service: Failed with result 'exit-code'.
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