Verification for Focal (245.4-4ubuntu3.8) # Initial repro on focal:
root@focal:~# md5sum /etc/resolv.conf; stat -t -L /etc/resolv.conf fbfde622ae28a4dcfbf73a397a10c6ae /etc/resolv.conf /etc/resolv.conf 717 8 81a4 101 103 76 123 1 0 0 1625844292 1625844273 1625844273 0 4096 root@focal:~# ip link set eth0 down; sleep 1; ip link set eth0 up root@focal:~# md5sum /etc/resolv.conf; stat -t -L /etc/resolv.conf fbfde622ae28a4dcfbf73a397a10c6ae /etc/resolv.conf /etc/resolv.conf 717 8 81a4 101 103 76 123 1 0 0 1625844310 1625844308 1625844308 0 4096 # Upgrading to -proposed root@focal:~# apt update && apt-get dist-upgrade -V Get:1 http://security.ubuntu.com/ubuntu focal-security InRelease [114 kB] Hit:2 http://archive.ubuntu.com/ubuntu focal InRelease Get:3 http://archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB] Get:4 http://archive.ubuntu.com/ubuntu focal-proposed InRelease [267 kB] Get:5 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages [1,086 kB] Get:6 http://archive.ubuntu.com/ubuntu focal-updates/main Translation-en [239 kB] Get:7 http://archive.ubuntu.com/ubuntu focal-updates/universe amd64 Packages [840 kB] Get:8 http://archive.ubuntu.com/ubuntu focal-proposed/restricted amd64 Packages [191 kB] Get:9 http://archive.ubuntu.com/ubuntu focal-proposed/restricted Translation-en [27.2 kB] Get:10 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 Packages [203 kB] Get:11 http://archive.ubuntu.com/ubuntu focal-proposed/main Translation-en [42.2 kB] Get:12 http://archive.ubuntu.com/ubuntu focal-proposed/multiverse amd64 Packages [18.2 kB] Get:13 http://archive.ubuntu.com/ubuntu focal-proposed/multiverse Translation-en [6,732 B] Get:14 http://archive.ubuntu.com/ubuntu focal-proposed/universe amd64 Packages [56.2 kB] Get:15 http://archive.ubuntu.com/ubuntu focal-proposed/universe Translation-en [24.5 kB] Fetched 3,229 kB in 2s (1,428 kB/s) Reading package lists... Done Building dependency tree Reading state information... Done 9 packages can be upgraded. Run 'apt list --upgradable' to see them. Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... Done The following packages will be upgraded: libgnutls30 (3.6.13-2ubuntu1.3 => 3.6.13-2ubuntu1.5) libnss-systemd (245.4-4ubuntu3.7 => 245.4-4ubuntu3.8) libpam-systemd (245.4-4ubuntu3.7 => 245.4-4ubuntu3.8) libsystemd0 (245.4-4ubuntu3.7 => 245.4-4ubuntu3.8) libudev1 (245.4-4ubuntu3.7 => 245.4-4ubuntu3.8) systemd (245.4-4ubuntu3.7 => 245.4-4ubuntu3.8) systemd-sysv (245.4-4ubuntu3.7 => 245.4-4ubuntu3.8) systemd-timesyncd (245.4-4ubuntu3.7 => 245.4-4ubuntu3.8) udev (245.4-4ubuntu3.7 => 245.4-4ubuntu3.8) 9 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 6,672 kB of archives. After this operation, 15.4 kB of additional disk space will be used. Do you want to continue? [Y/n] Get:1 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 libnss-systemd amd64 245.4-4ubuntu3.8 [96.1 kB] Get:2 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 udev amd64 245.4-4ubuntu3.8 [1,365 kB] Get:3 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 libudev1 amd64 245.4-4ubuntu3.8 [78.4 kB] Get:4 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 systemd-sysv amd64 245.4-4ubuntu3.8 [10.3 kB] Get:5 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 systemd-timesyncd amd64 245.4-4ubuntu3.8 [28.1 kB] Get:6 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 libpam-systemd amd64 245.4-4ubuntu3.8 [186 kB] Get:7 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 libgnutls30 amd64 3.6.13-2ubuntu1.5 [828 kB] Get:8 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 systemd amd64 245.4-4ubuntu3.8 [3,810 kB] Get:9 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 libsystemd0 amd64 245.4-4ubuntu3.8 [271 kB] Fetched 6,672 kB in 3s (2,541 kB/s) (Reading database ... 14718 files and directories currently installed.) Preparing to unpack .../libnss-systemd_245.4-4ubuntu3.8_amd64.deb ... Unpacking libnss-systemd:amd64 (245.4-4ubuntu3.8) over (245.4-4ubuntu3.7) ... Preparing to unpack .../udev_245.4-4ubuntu3.8_amd64.deb ... Unpacking udev (245.4-4ubuntu3.8) over (245.4-4ubuntu3.7) ... Preparing to unpack .../libudev1_245.4-4ubuntu3.8_amd64.deb ... Unpacking libudev1:amd64 (245.4-4ubuntu3.8) over (245.4-4ubuntu3.7) ... Setting up libudev1:amd64 (245.4-4ubuntu3.8) ... (Reading database ... 14718 files and directories currently installed.) Preparing to unpack .../systemd-sysv_245.4-4ubuntu3.8_amd64.deb ... Unpacking systemd-sysv (245.4-4ubuntu3.8) over (245.4-4ubuntu3.7) ... Preparing to unpack .../systemd-timesyncd_245.4-4ubuntu3.8_amd64.deb ... Unpacking systemd-timesyncd (245.4-4ubuntu3.8) over (245.4-4ubuntu3.7) ... Preparing to unpack .../libpam-systemd_245.4-4ubuntu3.8_amd64.deb ... Unpacking libpam-systemd:amd64 (245.4-4ubuntu3.8) over (245.4-4ubuntu3.7) ... Preparing to unpack .../libgnutls30_3.6.13-2ubuntu1.5_amd64.deb ... Unpacking libgnutls30:amd64 (3.6.13-2ubuntu1.5) over (3.6.13-2ubuntu1.3) ... Setting up libgnutls30:amd64 (3.6.13-2ubuntu1.5) ... (Reading database ... 14718 files and directories currently installed.) Preparing to unpack .../systemd_245.4-4ubuntu3.8_amd64.deb ... Unpacking systemd (245.4-4ubuntu3.8) over (245.4-4ubuntu3.7) ... Preparing to unpack .../libsystemd0_245.4-4ubuntu3.8_amd64.deb ... Unpacking libsystemd0:amd64 (245.4-4ubuntu3.8) over (245.4-4ubuntu3.7) ... Setting up libsystemd0:amd64 (245.4-4ubuntu3.8) ... Setting up udev (245.4-4ubuntu3.8) ... Setting up systemd (245.4-4ubuntu3.8) ... Installing new version of config file /etc/dhcp/dhclient-enter-hooks.d/resolved ... Setting up systemd-timesyncd (245.4-4ubuntu3.8) ... Setting up systemd-sysv (245.4-4ubuntu3.8) ... Setting up libnss-systemd:amd64 (245.4-4ubuntu3.8) ... Setting up libpam-systemd:amd64 (245.4-4ubuntu3.8) ... Processing triggers for libc-bin (2.31-0ubuntu9.2) ... Processing triggers for dbus (1.12.16-2ubuntu2.1) ... # Config the fix worked: root@focal:~# md5sum /etc/resolv.conf; stat -t -L /etc/resolv.conf fbfde622ae28a4dcfbf73a397a10c6ae /etc/resolv.conf /etc/resolv.conf 717 8 81a4 101 103 76 50 1 0 0 1625844400 1625844368 1625844368 0 4096 root@focal:~# ip link set eth0 down; sleep 1; ip link set eth0 up root@focal:~# md5sum /etc/resolv.conf; stat -t -L /etc/resolv.conf fbfde622ae28a4dcfbf73a397a10c6ae /etc/resolv.conf /etc/resolv.conf 717 8 81a4 101 103 76 50 1 0 0 1625844407 1625844368 1625844368 0 4096 ** Tags removed: verification-needed-focal ** Tags added: verification-done-focal -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1891215 Title: systemd-resolved re-creates /run/systemd/resolve/*resolv.conf for every IPv6 RA received Status in systemd: Unknown Status in systemd package in Ubuntu: Fix Released Status in systemd source package in Bionic: New Status in systemd source package in Focal: Fix Committed Status in systemd source package in Groovy: Fix Committed Status in systemd source package in Hirsute: Fix Committed Bug description: [impact] networking changes, like RA events, can cause systemd-resolved to re- write the resolv.conf file, even if the contents didn't change, resulting in unnecessary increased amount of inotify events [test case] see original description for ipv6ra-related reproducer, or simple reproducer here: configure networkd with some config for (e.g.) eth0, but not a config that would result in /etc/resolv.conf changing when the interface goes up/down - for example, use static config with no DNS search domains. Then bring eth0 up/down while observing the md5sum (file content) does not change but the mtime does change. root@lp1891215-h:~# ip l set down dev eth0 root@lp1891215-h:~# md5sum /etc/resolv.conf db23e80078515192c312e5f321ff0340 /etc/resolv.conf root@lp1891215-h:~# stat -t -L /etc/resolv.conf /etc/resolv.conf 740 8 81a4 101 103 fc 188 1 0 0 1625238218 1625238216 1625238216 0 4096 root@lp1891215-h:~# ip l set up dev eth0 root@lp1891215-h:~# md5sum /etc/resolv.conf db23e80078515192c312e5f321ff0340 /etc/resolv.conf root@lp1891215-h:~# stat -t -L /etc/resolv.conf /etc/resolv.conf 740 8 81a4 101 103 fc 188 1 0 0 1625238227 1625238226 1625238226 0 4096 [regression potential] regressions would result in incorrect or missing data in the resolv.conf file, possibly resulting in dns failures or errors [scope] this is needed for h and eralier this is (potentially) fixed upstream by f3e1f00d03445911ee73729219cea88c8a70c612 which in first included in v248, so this is needed in hirsute and earlier [original description] # Issue description: On 2 Linode VMs that are used as lxd hosts, we noticed that /run/systemd/resolve/*resolv.conf were re-created quite frequently (~ once per second). We noticed because of the log noise from lxd's dnsmasq instance using inotify to watch the target of /etc/resolv.conf (which points to the stub-resolv.conf in our case). This was (wrongly) reported as a lxd bug (https://github.com/lxc/lxd/issues/7765) until it became apparent it was more likely to be a problem with systemd(-resolved)?. The log noise is the observable problem that would be nice to see addressed: root@lxd02:~# uptime 17:55:48 up 9:52, 1 user, load average: 0.18, 0.11, 0.05 root@lxd02:~# journalctl -b0 | grep -cF dnsmasq 158609 Upon further investigation, it seems that systemd-resolved re-creates the resolv.conf and stub-resolv.conf files whenever an IPv6 RA is received. 1) One can observe that by setting systemd-resolved's service in debug mode: $ sudo systemctl edit systemd-resolved and in the editor that is opened, add and save this content: [Service] Environment=SYSTEMD_LOG_LEVEL=debug then restart systemd-resolved and watch the logs scroll by with: $ journalctl -fu systemd-resolved 3) In another terminal, watch the files be recreated with: watch -d -n 0.1 stat /run/systemd/resolve/stub-resolv.conf 3) In yet another terminal, run a packet capture and watch "ICMP6, router advertisement" messages come by: sudo tcpdump -ni eth0 icmp6 You will see that every time a RA packet comes in, resolved's journal will log this: Aug 11 17:33:55 lxd02 systemd-resolved[15368]: Sent message type=signal sender=n/a destination=n/a path=/org/freedesktop/resolve1 interface=org.freedesktop.DBus.Properties member=PropertiesChanged cookie=244 reply_cookie=0 signature=sa{sv}as error-name=n/a error- message=n/a And the stat monitoring terminal will blink to highlight the new inode and timestamps of the freshly replaced stub-resolv.conf file. # Additional information: root@lxd02:~# lsb_release -rd Description: Ubuntu 20.04.1 LTS Release: 20.04 root@lxd02:~# apt-cache policy systemd systemd: Installed: 245.4-4ubuntu3.2 Candidate: 245.4-4ubuntu3.2 Version table: *** 245.4-4ubuntu3.2 500 500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages 100 /var/lib/dpkg/status 245.4-4ubuntu3 500 500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages root@lxd02:~# uname -a Linux lxd01 5.4.0-42-generic #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux To manage notifications about this bug go to: https://bugs.launchpad.net/systemd/+bug/1891215/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
