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| slanck | i got a kernel crash dump and would like to analyze it with GDB but the .crash file on /var/crash doesn't seem to have a CoreDump file when I unpack it using apport-unpack | 15:00 |
|---|---|---|
| slanck | and using the .crash file or the file generated on /var/crash/DATE/dump.XYZ with GDB gives incorrect file format | 15:01 |
| slanck | I would like to have the CoreDump file to analyze it using GDB, apport-retrace gives the error of missing files | 15:02 |
| slanck | it's working now | 16:04 |
| gpiccoli | slanck, you need to use the crash tool in order to analyze kernel dumps | 16:05 |
| gpiccoli | need was a strong statement...it's recomended that you use the crash tool, it's meant to that heheh | 16:05 |
| gpiccoli | for userspace core dumps, gdb is usually the proper tool =) | 16:06 |
| slanck | gpiccoli: hi | 16:07 |
| slanck | yes, I was using the crash command. The issue was that, i don't know yet why, but the dump.XYZ file generated on /var/crash/ was kind of incomplete | 16:08 |
| slanck | i regenerated the crash using echo c > /proc/sysrq... and now the dump.XYZ file worked as expected using crash | 16:08 |
| slanck | the first dump is not detected as a kdump file | 16:09 |
| slanck | sudo file 202007010222/dump.202007010222 | 16:09 |
| slanck | 202007010222/dump.202007010222: data | 16:09 |
| slanck | sudo file 202007011558/dump.202007011558 | 16:10 |
| slanck | 202007011558/dump.202007011558: Kdump compressed dump v6, system Linux, | 16:10 |
| slanck | i don't know what happened, when the first dump file was generated, i didn't have the linux-crashdump package installed even though there was a crash command available on my system | 16:11 |
| slanck | i then installed the linux-crashdump and generated a new crash and got the result shown above, i guess is that, without linux-crashdump, it generates a dump but kind of incomplete | 16:11 |
| slanck | when i installed linux-crashdump, it didn't replace the crash tool i had already on my system, i checked the version and it's the same | 16:12 |
| slanck | crash 7.2.8 | 16:12 |
| slanck | gpiccoli: thank you anyways | 16:14 |
| gpiccoli | slanck, interesting, so you got a bad dump on the first time. The package linux-crashdump is a meta pkg that maps to all usually required packages to have kdump working | 16:16 |
| gpiccoli | the real packages you need to collect the dump properly (and they all come with linux-crashdump) are kexec-tools, kdump-tools and makedumpfile | 16:16 |
| gpiccoli | The crash package (also included on the metapkg) brings the crash binary to analyze the vmcore =) | 16:17 |
| slanck | @gpiccoli thank you very much, the bad dump was generated triggering a kernel bug and the good dump shown above was generated using echo c > /proc/sysrq, it's worth to mention I am working on a custom kernel | 16:22 |
| slanck | i will trigger the bug again later today and see if it generates a "good" dump now that I've installed linux-crashdump | 16:23 |
| gpiccoli | awesome, hope it works! | 16:25 |
| gpiccoli | What version of Ubuntu are you suing ? | 16:25 |
| gpiccoli | *using | 16:25 |
| gpiccoli | I suggest to increase a bit the crashkernel memory if it's not working reliably, also worth trying to capture the console output during the kdump kernel boot | 16:26 |
| slanck | Ubuntu 20.04, it's a custom kernel based on vmlinuz-5.4.0-37-generic | 16:26 |
| slanck | i had some issues with crashkernel I guess because I am using a KASAN-enabled kernel | 16:27 |
| slanck | initially the system was only able to boot properly when I configured the VM with more or equal 6GB of RAM, less than that and I got a crash during boot | 16:28 |
| slanck | with 6GB of RAM, i had to increase crashkernel memory up to the point I got kdump properly configured and working | 16:29 |
| slanck | with working I mean being able to load the kexec kernel and creating a dump file on /var/crash but I didn't need to investigate the dump file until today | 16:30 |
| slanck | I had to set crashkernel=2048M to get to that point | 16:30 |
| slanck | oh, sorry, the VM has 12GB of RAM and crashkernel=2048M | 16:31 |
| slanck | i triggered the kernel bug again and now it seems it working fine, the issue seems to be that the package linux-crashdump was missing | 16:34 |
| slanck | it kind of works, i don't have the registers when the system crashed | 16:49 |
| slanck | crash> i r | 16:49 |
| slanck | The program has no registers now. | 16:49 |
| slanck | gdb: gdb request failed: i r | 16:49 |
| slanck | crash> | 16:49 |
| slanck | sudo crash vmlinux_symbols dump.202007011645 | 16:50 |
| gpiccoli | is "i r" a command on crash? I'm not sure | 17:41 |
| gpiccoli | try checking some structure or some pointer you know the address, like linux_banner or something like this | 17:41 |
| weskrasko | Hi, #nm sent me here. I followed some instructions on a site to fix my Nvidia drivers, ran "sudo ubuntu-drivers autoinstall", fixed Nvidia but then after reboot, all my network interfaces are gone! | 21:38 |
| weskrasko | So I ran ip link show as recommended in other channel. Shows only lo. | 21:39 |
| weskrasko | Ran lspci, shows Ethernet and Wireless cards, but dmesg doesn't seem to show any of that. | 21:39 |
| weskrasko | They said maybe my kernel is now not loading the firmware/driver/module's needed? I don't know what happened, my wifi was working "out of the box" before this. | 21:40 |
| jeremy31 | weskrasko: was there a recent kernel update? You might want to see if the linux-modules-extra was also installed for that kernel version | 22:25 |
| weskrasko | Thanks, how would I do that? | 22:26 |
| weskrasko | And yes, right after I ran the command above I did a normal update as I always do, I saw kernel and firmware stuff. NEver had an issue with udpating so thought nothing of it. | 22:27 |
| jeremy31 | weskrasko: check in terminal> dpkg -l | grep linux-modules-extra-$(uname -r) | 22:28 |
| weskrasko | Nope, no limux-modules-extra for current kernel | 22:36 |
| weskrasko | How can I fix with NO connection? Download deb? | 22:36 |
| jeremy31 | weskrasko: you can use grub menu to boot into older kernel, then install the linux-modules-extra for the newer kernel | 22:38 |
| weskrasko | OMG thank you it worked!! Never had that happen before, but at least it's back up. :) | 22:43 |
| sarnold | jeremy31: nice :D | 22:43 |
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