On Fri, Dec 14, 2018 at 05:23:35PM +0000, Alan Reding wrote: > To block IPv6 traffic, I do the following: > > 1. Add the following line to /etc/default/grub > > GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" > > 2. Run update-grub > > 3. In /etc/hosts, add # in front of all lines that mention IPv6 hosts > > 3. Reboot machine > > To re-enable IPv6 traffic, I do the following: [...]
GRUB just passes the stuff in GRUB_CMDLINE_LINUX_DEFAULT straight through to the kernel; it has no other involvement in how the operating system's networking stack is set up. This could only possibly be a GRUB bug if you're finding that update-grub isn't correctly transferring GRUB_CMDLINE_LINUX_DEFAULT into /boot/grub/grub.cfg, or if the kernel parameters are somehow not actually being passed to the kernel (which you can check after boot by looking in /proc/cmdline). Otherwise, this cannot possibly be a GRUB bug, and I'd appreciate it if you could either close it or figure out some other suitable package to reassign it to, as appropriate. > Method A > > 4. Add # in front of the line that contains > GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" as in below: > > #GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" > > 5. Run update-grub > > 6. In /etc/hosts, remove # from all lines that mention IPv6 hosts > > 7. Reboot machine > > Result: IPv6 traffic is still blocked > > Method B > > 8. In /etc/default/grub, I delete the line > GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" > > 9. Run update-grub > > 10. In /etc/hosts, I ensure that # does not appear in front of lines that > mention IPv6 hosts > > 11. Reboot machine > > Result: IPv6 traffic is still blocked > > Method C > > 12. In /etc/default/grub, I change the value of ipv6.disable=0 as in: > > GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=0 quiet" > > 13. Run update-grub > > 14. In /etc/hosts, I ensure that # does not appear in front of lines that > mention IPv6 hosts > > 15. Reboot machine > > Result: IPv6 traffic is NOT blocked. IPv6 traffic is re-enabled These symptoms indicate to me that the equivalent of ipv6.disable=1 is being set somewhere else *as well*, which causes things to only work properly if you explicitly pass the kernel argument ipv6.disable=0. I'd suggest looking around in /etc/, perhaps /etc/modprobe.d/. -- Colin Watson [cjwat...@debian.org]
