Date: Mon, 8 Nov 2021 22:57:04 +0300 From: Rozhuk Ivan <rozhuk.im@gmail.com> To: Alexander <alex@alexslomka.xyz> Cc: "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Subject: Re: Problems with getting a crash dump Message-ID: <20211108225704.243752a6@rimwks.local> In-Reply-To: <v5_t5VART-vha7P8SGBRZ35WvfTGSjVObzcgu3dTOMyCnkmFx7yDSDPCVI-MeKICc9HZ7xDJtBJRHq0xxFtUMBO8oiMWqRO62t8Vlebb9rw=@alexslomka.xyz> References: <v5_t5VART-vha7P8SGBRZ35WvfTGSjVObzcgu3dTOMyCnkmFx7yDSDPCVI-MeKICc9HZ7xDJtBJRHq0xxFtUMBO8oiMWqRO62t8Vlebb9rw=@alexslomka.xyz>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, 08 Nov 2021 19:08:31 +0000 Alexander <alex@alexslomka.xyz> wrote: > Hello, I am currently using FreeBSD 14.0-CURRENT and I found a bug > that triggers a kernel panic. I wanted to make a kernel crash dump to > further investigate the issue, but after a few tries I still did not > manage to do it. I started by following the instructions in the > FreeBSD Handbook. I checked that /dev/nvd0p2.eli is an active swap > device and I configured it to be used as a dump device like this: > > # dumpon -v /dev/nvd0p2.eli > # sysctl debug.kdb.panic=1 > > Then I booted into single user mode to extract the core dumb: > > # savecore -vC /dev/nvd0p2 > checking for kernel dump on device /dev/nvd0p2 > mediasize = 2147483648 bytes > sectorsize = 512 bytes > magic mismatch on last dump header on /dev/nvd0p2 > No dump exists > > A you can see the core dump was not written to the device. Later I > also tried using /dev/nvd0p2 (with out the "eli" part), because > /dev/nvd0p2.eli is only available after I enable it using swapon, but > the handbook states the I should first extract the dump, before I use > the device as swap again. But the result was the same. /dev/nvd0p2 is > only 2gb in size and it's an encrypted swap device, so I thought that: > 1) Maybe the size of the device is to small even for a minidump. > 2) Perhaps using encrypted swap as a dump device is not supported. > > Because of those complications I decided to use an external 8gb USB > drive as my dump device. > > # gpart create -s gpt /dev/da0 > # gpart add -t freebsd-swap /dev/da0 > # swapoff -a > # swapon /dev/da0p1 > # dumpon -v /dev/da0p1 > kernel dumps on priority: device > 0: da0p1 > > I have 8gb of RAM so a 8gb dump device should be big enough for a > minidump. I used `sysctl debug.kdb.panic=1` to crash the kernel and > rebooted the system. I also waited for 10 minutes to ensure the the > kernel finished writing the core dump to the device. > > # savecore -vC /dev/da0p1 > checking for kernel dump on device /dev/da0p1 > mediasize = 7744741376 bytes > sectorsize = 512 bytes > magic mismatch on last dump header on /dev/da0p1 > No dump exists > > As you can see I still did not manage to get a kernel crash dump. Any > ideas? > > Here is a picture of the output I get after running `sysctl > debug.kdb.panic=1`: > https://forums.freebsd.org/attachments/img_20211108_163313-jpeg.11936/ > > PS yes kern.coredump is set to 1. > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238301 http://netlab.dhis.org/wiki/ru:software:freebsd:kernel_debug It work for 12 and 13, may be 14 have bugs/changes.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20211108225704.243752a6>