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Accepted
Ali Razmdideh
Asked: 2017-04-28 06:50:17 +0800 CST

systemd-resolve high cpu usage after update to 17.04

  • 772

I have recently upgrade my Xubuntu from 16.10 to 17.04.

Every things works well except systemd-resolve. some times it makes cpu usage too high and I don't know why this issue has been happend.

And here is the top command output:

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                               
  1114 systemd+  20   0   51532   6744   4504 R   100  0.0   9:51.67 systemd-resolve                       
  1152 dnsmasq   20   0   64360   2892   2480 R  38.9  0.0   4:05.53 dnsmasq                               
  1245 root      20   0  376644  89644  64436 S   1.7  0.5   0:35.69 Xorg                                  
  1624 asus      20   0  370160  45820  28488 S   0.7  0.3   0:00.90 python2                               
  2238 asus      20   0 2562816 553112 128492 S   0.7  3.4   2:41.20 firefox                               
    16 root      20   0       0      0      0 S   0.3  0.0   0:01.05 ksoftirqd/1                           
   708 root     -51   0       0      0      0 S   0.3  0.0   0:01.20 irq/95-ELAN1000                       
  1302 root     -51   0       0      0      0 S   0.3  0.0   0:03.68 irq/142-nvidia                        
  1734 asus      20   0  483388  11060   8560 S   0.3  0.1   0:05.45 conky                                 
  2820 root      20   0       0      0      0 S   0.3  0.0   0:00.14 kworker/5:1                           
  3420 asus      20   0   53384   3932   3200 R   0.3  0.0   0:00.76 top

I don't know why this issue has been happend but usually it's occured when run some commands like sudo apt update .

(I'm using tor and obfs4proxy, It's may be helpful for answer)

xubuntu

4 Answers

  1. Best Answer

    I had a similar conflict between systemd-resolve and dnsmasq on port 53.

    https://unix.stackexchange.com/questions/304050/how-to-avoid-conflicts-between-dnsmasq-and-systemd-resolved

    and

    https://github.com/systemd/systemd/pull/4061

    led me to add DNSStubListener=no in /etc/systemd/resolved.conf and then sudo service systemd-resolved restart.

    • 37

  2. Caused Problems with other Apps (teamViewer in my case)

    Suggested by another Steps of solution

    Add the line DNSMASQ_EXCEPT=lo to /etc/default/dnsmasq

    sudo nano /etc/default/dnsmasq

    Restart dnsmasq via

    sudo service systemd-resolved restart

    Say Thanks If I helped, It went back to normal and does NOT screw around with other apps, as the previous method DID.

    Cheers, Mark

    • 25

  3. systemd-resolved gets crazy when somebody modifies the file /etc/resolv.conf, which is meant to be pointing to its own listening address 127.0.0.53.

    That somebody could be any script triggered by networking events (VPN coming up, or down, DHCP, etc.)

    If you set the nameserver back to 127.0.0.53, then systemd-resolved will "calm down" few seconds later.

    Assuming that everybody's respecting the rules, and only using resolvconf for modifying the resolver's configuration, you can also do this:

    The file /etc/resolvconf/interface-order specifies the order in which nameservers will be used, depending on the network interface they were received from.

    If you add an entry for systemd-resolved at the top of the file, it will always be considered first and the file will not be modified.

    • 10

  4. I had the same Problem in 18.04. systemd-resolved and dnsmasq tend to loop. I solved it this way:

    Add or uncomment the following line in /etc/default/dnsmasq:

    IGNORE_RESOLVCONF=yes

    Create your own resolv file (/etc/resolv.personal) to define nameservers. You can use any nameserver here. I took two from OpenNIC.

    nameserver 5.132.191.104
nameserver 103.236.162.119

    In /etc/dnsmasq.conf add or uncomment the following line:

    resolv-file=/etc/resolv.personal

    Then restart dnsmasq and disable the default resolver: systemd-resolved.

    sudo service dnsmasq restart
sudo systemctl stop systemd-resolved
sudo systemctl disable systemd-resolved
    • 2