教你如何捕捉内核崩溃信息
首先安装必选包：
apt-get -y install aptitude kdump-tools crash kexec-tools makedumpfile linux-image-`uname -r`-dbg aptitude full-upgrade # 避免运行的内核版本与调试的版本不一致导致无法调试
Kdump配置文件 /etc/default/kdump-tools 关键部分
USE_KDUMP=1 KDUMP_SYSCTL="kernel.panic_on_oops=1" KDUMP_KERNEL=/boot/vmlinuz-3.16.0-4-amd64 KDUMP_INITRD=/boot/initrd.img-3.16.0-4-amd64 KDUMP_COREDIR="/data/crash" KDUMP_FAIL_CMD="reboot -f" DEBUG_KERNEL=/usr/lib/debug/vmlinux-3.16.0-4-amd64 MAKEDUMP_ARGS="-c -d 31" KDUMP_CMDLINE="crashkernel=512M"
crashkernel大小配比，正常情况崩溃后1分钟左右会自动重启、配置不正确会导致重启卡住黑屏不动。
内存大小 crashkernel= 0 - 12G 128M 13 - 48G 256M 49 - 128G 512M 129 - 256G 1G *(896M, 768M o或 512M)
Grub配置文件/etc/default/grub关键部分
GRUB_CMDLINE_LINUX_DEFAULT="nmi_watchdog=1 crashkernel=512M"
Sysctl配置文件/etc/sysctl.conf关键部分
kernel.sysrq = 1 kernel.watchdog = 1 kernel.nmi_watchdog = 1 kernel.panic_on_oops = 1 kernel.softlockup_panic = 1 kernel.watchdog_thresh = 10
重启让配置生效
update-grub reboot -f kdump-config load kdump-config show
校验
# cat /proc/cmdline BOOT_IMAGE=/boot/vmlinuz-3.16.0-4-amd64 root=UUID=a58ab901-00aa-4f8b-b3eb-d352fc72233 ro net.ifnames=0 thash_entries=1048576 rhash_entries=1048576 biosdevname=0 nohz=off enforcing=0 ipv6.disable_ipv6=1 nmi_watchdog=1 selinux=0 transparent_hugepage=never cgroup_enable=memory swapaccount=1 vga=771 crashkernel=512M # kdump-config test USE_KDUMP: 1 KDUMP_SYSCTL: kernel.panic_on_oops=1 KDUMP_COREDIR: /data/crash crashkernel addr: 0x2e000000 kdump kernel addr: kdump kernel: /boot/vmlinuz-3.16.0-4-amd64 kdump initrd: /boot/initrd.img-3.16.0-4-amd64 debug kernel: /usr/lib/debug/vmlinux-3.16.0-4-amd64 kexec command to be used: /sbin/kexec -p --command-line="BOOT_IMAGE=/boot/vmlinuz-3.16.0-4-amd64 root=UUID=a58ab901-00aa-4f8b-b3eb-d352fc7f6acb ro net.ifnames=0 thash_entries=1048576 rhash_entries=1048576 biosdevname=0 nohz=off enforcing=0 ipv6.disable_ipv6=1 nmi_watchdog=1 selinux=0 transparent_hugepage=never cgroup_enable=memory swapaccount=1 vga=771 irqpoll maxcpus=1 nousb systemd.unit=kdump-tools.service crashkernel=512M" --initrd=/boot/initrd.img-3.16.0-4-amd64 /boot/vmlinuz-3.16.0-4-amd64
测试
echo c > /proc/sysrq-trigger
分析
crash /data/crash/201609010252/dump.201609012233 /usr/lib/debug/lib/modules/3.16.0-4-amd64/vmlinux
开始欢快的调试之旅
常用错误 ：
WARNING: kernel version inconsistency between vmlinux and dumpfile # 版本不一致，full-upgrade 一下。 崩溃后系统不重启。 # 请检查 sysctl 、 crashkernel 及 nmi_watchdog 的设定！
