Bug#916457: grub2-common: Grub refuses to re-enable IPv6 traffic
On Sun, Dec 16, 2018 at 02:34:57PM +, Alan Reding wrote: > Following your reply, I did a test which consisted of the following steps: > > 1. I ran sudo gedit /etc/default/grub, deleted/removed > GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet", ran sudo update-grub and > rebooted my machine. > > 2. Immediately after the reboot, I issued the command nano /proc/cmdline and > below is the result: > > BOOT_IMAGE=/boot/vmlinuz-4.18.0-0.bpo.1-amd64 root=UUID=[string of > alphanumeric characters] ro ipv6.disable=1 quiet > > 3. Next, I ran the command sudo grep -RF ipv6.disable /etc and below is the > result: > > /etc/default/grub.ucf-old:#GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" > /etc/default/grub:GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" > > I am puzzled why ipv6.disable=1 quiet appears in the above results of (2) and > (3) despite the fact that I had deleted/removed > GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" from /etc/default/grub. I'll need to see the full contents of /etc/default/grub and /boot/grub/grub.cfg immediately after running step 1 above. (No need to reboot.) -- Colin Watson [cjwat...@debian.org]
Bug#916457: grub2-common: Grub refuses to re-enable IPv6 traffic
Hello Colin Thanks for your response. Following your reply, I did a test which consisted of the following steps: 1. I ran sudo gedit /etc/default/grub, deleted/removed GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet", ran sudo update-grub and rebooted my machine. 2. Immediately after the reboot, I issued the command nano /proc/cmdline and below is the result: BOOT_IMAGE=/boot/vmlinuz-4.18.0-0.bpo.1-amd64 root=UUID=[string of alphanumeric characters] ro ipv6.disable=1 quiet 3. Next, I ran the command sudo grep -RF ipv6.disable /etc and below is the result: /etc/default/grub.ucf-old:#GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" /etc/default/grub:GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" I am puzzled why ipv6.disable=1 quiet appears in the above results of (2) and (3) despite the fact that I had deleted/removed GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 quiet" from /etc/default/grub. Regards. Alan Reding On Fri, 12/14/18, Colin Watson wrote: Subject: Re: Bug#916457: grub2-common: Grub refuses to re-enable IPv6 traffic To: "Alan Reding" , 916...@bugs.debian.org Date: Friday, December 14, 2018, 10:56 PM On Fri, Dec 14, 2018 at 05:23:35PM +, 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] -Inline Attachment Follows-
Bug#916457: grub2-common: Grub refuses to re-enable IPv6 traffic
On Fri, Dec 14, 2018 at 05:23:35PM +, 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]
