today i upgrade ubuntu from 15.04 to 16.04, after that my tor is down and i have the problem on /var/log/tor/log :
Apr 25 07:52:58.678 [warn] OpenSSL version from headers does not match the version we're running with. If you get weird crashes, that might be why. (Compiled with 1000207f: OpenSSL 1.0.2g 1 Mar 2016; running with 1000207f: OpenSSL 1.0.2g-fips 1 Mar 2016).
Apr 25 07:52:58.702 [notice] Tor v0.2.7.6 (git-605ae665009853bd) running on Linux with Libevent 2.0.21-stable, OpenSSL 1.0.2g-fips and Zlib 1.2.8. Apr 25 07:52:58.702 [notice] Tor can't help you if you use it wrong! Learn how to be safe at https://www.torproject.org/download/download#warning Apr 25 07:52:58.702 [notice] Read configuration file "/usr/share/tor/tor-service-defaults-torrc".
Apr 25 07:52:58.702 [notice] Read configuration file "/etc/tor/torrc". Apr 25 07:52:58.705 [notice] Opening Socks listener on 127.0.0.1:9050 Apr 25 07:52:58.706 [notice] Opening Control listener on /var/run/tor/control
Apr 25 07:52:58.000 [notice] Parsing GEOIP IPv4 file /usr/share/tor/geoip. Apr 25 07:52:58.000 [notice] Parsing GEOIP IPv6 file /usr/share/tor/geoip6.
Apr 25 07:52:58.000 [notice] Bootstrapped 0%: Starting Apr 25 07:52:58.000 [notice] Delaying directory fetches: No running bridges
Apr 25 07:52:58.000 [notice] Signaled readiness to systemd Apr 25 07:52:59.000 [warn] Could not launch managed proxy executable at '/usr/bin/obfs4proxy' ('Operation not permitted'). Apr 25 07:53:00.000 [notice] Bootstrapped 5%: Connecting to directory server
Apr 25 07:53:00.000 [warn] We were supposed to connect to bridge '126.96.36.199:38617' using pluggable transport 'obfs4', but we can't find a pluggable transport proxy supporting 'obfs4'. This can happen if you haven't provided a ClientTransportPlugin line, or if your pluggable transport proxy stopped running.
Apr 25 07:53:00.000 [warn] Problem bootstrapping. Stuck at 5%: Connecting to directory server. (Can't connect to bridge; PT_MISSING; count 1; recommendation warn; host 9E255A5456143C435D0EADAB1473A3884A29C8C4 at 188.8.131.52:38617)