一台服务器设备，反复重启，每天重启数次。
一： 原因分析及初步排异。
1. 硬件，内存主板，一一更换，甚至除了硬盘将整台机器都换掉了，依然重启。
2. 排除电源问题，换了电源线，换了插座，还是重启。
3. 那么接下来，还有三种可能：
A。内核问题，内核crash。（redhat的稳定性还是十分让人信赖的，这种可能性不高）
B。硬盘或文件系统故障。本质上，这样会导致内核crash。
C。程序自主reboot。（我们自己的程序reboot，或进了黑客放了reboot脚本。好无聊的黑客。。。。）
二： 最好排除的，就是先解决内核的问题。
内核在crash那一刻是会发现，自己即将crash的，于是他会在临死前留下一些信息。告诉用户我发生了什么。 可是问题在于：文件系统的复杂性，会导致内核临死之前文件系统也随之崩溃了。
通过重启之后查看日志，确实没有留下有用的信息。
这是时候我们还有另一种手段，netcosole，他的功能是吧内核日志从socket以udp的方式，自组IP包而不走协议栈，讲包推出网卡端口。包的格式为syslog格式。
netcosole使用：
1. 修改配置文件
[root@S205 ~]# cat /etc/sysconfig/netconsole
# This is the configuration file for the netconsole service. By starting
# this service you allow a remote syslog daemon to record console output
# from this system. # The local port number that the netconsole module will use
LOCALPORT= # The ethernet device to send console messages out of (only set this if it
# can't be automatically determined)
DEV=enp3s0 # The IP address of the remote syslog server to send messages to
SYSLOGADDR=192.168.10.214 # The listening port of the remote syslog daemon
SYSLOGPORT= # The MAC address of the remote syslog server (only set this if it can't
# be automatically determined)
SYSLOGMACADDR=:8d:5c:::
[root@S205 ~]#
cat /etc/sysconfig/netconsole
2. 启动服务
[root@S205 ~]# systemctl start netconsole
[root@S205 ~]# systemctl enable netconsole
当前系统及内核版本：
[root@S205 ~]# cat /etc/redhat-release
CentOS Linux release 7.3. (Core)
[root@S205 ~]# uname -a
Linux S205 3.10.-.el7.x86_64 # SMP Tue Nov :: UTC x86_64 x86_64 x86_64 GNU/Linux
[root@S205 ~]#
成功收到内核crash日志：
Jul :: 192.168.10.205 [20239.422386] NMI watchdog: Watchdog detected hard LOCKUP on cpu
Jul :: 192.168.10.205
Jul :: 192.168.10.205 [20239.422529] Kernel panic - not syncing: Hard LOCKUP
Jul :: 192.168.10.205 [20239.422543] CPU: PID: Comm: swapper/ Not tainted 3.10.-.el7.x86_64 #
Jul :: 192.168.10.205 [20239.422561] Hardware name: LENOVO 10C0A038CD/ , BIOS FCKT73AUS //
Jul :: 192.168.10.205 [20239.422579] ffffffff818d9784
Jul :: 192.168.10.205 90a5d9572fc8872b
Jul :: 192.168.10.205 ffff88041edc5b18
Jul :: 192.168.10.205 ffffffff81685fac
Jul :: 192.168.10.205
Jul :: 192.168.10.205 [20239.422603] ffff88041edc5b98
Jul :: 192.168.10.205 ffffffff8167f3b3
Jul :: 192.168.10.205
Jul :: 192.168.10.205 ffff88041edc5ba8
Jul :: 192.168.10.205
Jul :: 192.168.10.205 [20239.422627] ffff88041edc5b48
Jul :: 192.168.10.205 90a5d9572fc8872b
Jul :: 192.168.10.205 ffff88041edc5ba8
Jul :: 192.168.10.205 ffffffff818d948a
Jul :: 192.168.10.205
Jul :: 192.168.10.205 [20239.422651] Call Trace:
Jul :: 192.168.10.205 [20239.422658] <NMI>
Jul :: 192.168.10.205 [<ffffffff81685fac>] dump_stack+0x19/0x1b
Jul :: 192.168.10.205 [20239.422678] [<ffffffff8167f3b3>] panic+0xe3/0x1f2
Jul :: 192.168.10.205 [20239.422692] [<ffffffff8108562f>] nmi_panic+0x3f/0x40
Jul :: 192.168.10.205 [20239.422706] [<ffffffff8112f0e6>] watchdog_overflow_callback+0xf6/0x100
Jul :: 192.168.10.205 [20239.422725] [<ffffffff8117465e>] __perf_event_overflow+0x8e/0x1f0
Jul :: 192.168.10.205 [20239.422741] [<ffffffff811752a4>] perf_event_overflow+0x14/0x20
Jul :: 192.168.10.205 [20239.422759] [<ffffffff81009d88>] intel_pmu_handle_irq+0x1f8/0x4e0
Jul :: 192.168.10.205 [20239.422776] [<ffffffff8168dbeb>] perf_event_nmi_handler+0x2b/0x50
Jul :: 192.168.10.205 [20239.422793] [<ffffffff8168f019>] nmi_handle.isra.+0x69/0xb0
Jul :: 192.168.10.205 [20239.422808] [<ffffffff8168f193>] do_nmi+0x133/0x410
Jul :: 192.168.10.205 [20239.422822] [<ffffffff8168e453>] end_repeat_nmi+0x1e/0x2e
Jul :: 192.168.10.205 [20239.422838] [<ffffffff8168d9c7>] ? _raw_spin_lock_irqsave+0x47/0x60
Jul :: 192.168.10.205 [20239.422855] [<ffffffff8168d9c7>] ? _raw_spin_lock_irqsave+0x47/0x60
Jul :: 192.168.10.205 [20239.422871] [<ffffffff8168d9c7>] ? _raw_spin_lock_irqsave+0x47/0x60
Jul :: 192.168.10.205 [20239.422887] <<EOE>>
Jul :: 192.168.10.205 <IRQ>
Jul :: 192.168.10.205 [<ffffffffa01fae23>] nvkm_fantog_update+0x43/0x110 [nouveau]
Jul :: 192.168.10.205 [20239.422947] [<ffffffffa01faf48>] nvkm_fantog_set+0x38/0x40 [nouveau]
Jul :: 192.168.10.205 [20239.422976] [<ffffffffa01fa378>] nvkm_fan_update+0xc8/0x210 [nouveau]
Jul :: 192.168.10.205 [20239.423005] [<ffffffffa01fa519>] nvkm_therm_fan_set+0x19/0x20 [nouveau]
Jul :: 192.168.10.205 [20239.423035] [<ffffffffa01f9b87>] nvkm_therm_update+0x97/0x310 [nouveau]
Jul :: 192.168.10.205 [20239.423064] [<ffffffffa01f9e17>] nvkm_therm_alarm+0x17/0x20 [nouveau]
Jul :: 192.168.10.205 [20239.423106] [<ffffffffa01fd2d3>] nvkm_timer_alarm_trigger+0x103/0x150 [nouveau]
Jul :: 192.168.10.205 [20239.423147] [<ffffffffa01fd3d0>] nvkm_timer_alarm+0x60/0xb0 [nouveau]
Jul :: 192.168.10.205 [20239.423176] [<ffffffffa01fb651>] alarm_timer_callback+0xd1/0xe0 [nouveau]
Jul :: 192.168.10.205 [20239.423207] [<ffffffffa01fd2d3>] nvkm_timer_alarm_trigger+0x103/0x150 [nouveau]
Jul :: 192.168.10.205 [20239.423238] [<ffffffffa01fd3d0>] nvkm_timer_alarm+0x60/0xb0 [nouveau]
Jul :: 192.168.10.205 [20239.423266] [<ffffffffa01faeea>] nvkm_fantog_update+0x10a/0x110 [nouveau]
Jul :: 192.168.10.205 [20239.423295] [<ffffffffa01faf0a>] nvkm_fantog_alarm+0x1a/0x20 [nouveau]
Jul :: 192.168.10.205 [20239.423324] [<ffffffffa01fd2d3>] nvkm_timer_alarm_trigger+0x103/0x150 [nouveau]
Jul :: 192.168.10.205 [20239.423355] [<ffffffffa01fd6fb>] nv04_timer_intr+0x6b/0xb0 [nouveau]
Jul :: 192.168.10.205 [20239.423384] [<ffffffffa01fd174>] nvkm_timer_intr+0x14/0x20 [nouveau]
Jul :: 192.168.10.205 [20239.423419] [<ffffffffa01ada87>] nvkm_subdev_intr+0x17/0x20 [nouveau]
Jul :: 192.168.10.205 [20239.423458] [<ffffffffa01ef7f9>] nvkm_mc_intr+0x79/0x110 [nouveau]
Jul :: 192.168.10.205 [20239.423486] [<ffffffffa01f4155>] nvkm_pci_intr+0x55/0xa0 [nouveau]
Jul :: 192.168.10.205 [20239.423503] [<ffffffff8113015e>] handle_irq_event_percpu+0x3e/0x1e0
Jul :: 192.168.10.205 [20239.423521] [<ffffffff8113033d>] handle_irq_event+0x3d/0x60
Jul :: 192.168.10.205 [20239.423536] [<ffffffff81133007>] handle_edge_irq+0x77/0x130
Jul :: 192.168.10.205 [20239.424012] [<ffffffff8102d26f>] handle_irq+0xbf/0x150
Jul :: 192.168.10.205 [20239.424491] [<ffffffff810f3c8a>] ? tick_check_idle+0x8a/0xd0
Jul :: 192.168.10.205 [20239.424967] [<ffffffff8169201a>] ? atomic_notifier_call_chain+0x1a/0x20
Jul :: 192.168.10.205 [20239.425445] [<ffffffff81698bef>] do_IRQ+0x4f/0xf0
Jul :: 192.168.10.205 [20239.425921] [<ffffffff8168dd6d>] common_interrupt+0x6d/0x6d
Jul :: 192.168.10.205 [20239.426389] <EOI>
Jul :: 192.168.10.205 [<ffffffff81514052>] ? cpuidle_enter_state+0x52/0xc0
Jul :: 192.168.10.205 [20239.426863] [<ffffffff81514199>] cpuidle_idle_call+0xd9/0x210
Jul :: 192.168.10.205 [20239.427314] [<ffffffff8103516e>] arch_cpu_idle+0xe/0x30
Jul :: 192.168.10.205 [20239.427793] [<ffffffff810e7c95>] cpu_startup_entry+0x245/0x290
Jul :: 192.168.10.205 [20239.428222] [<ffffffff8104f12a>] start_secondary+0x1ba/0x230
Jul :: 192.168.10.205 [ 2.633081] nouveau ::00.0: priv: HUB0: ffffffff (1b70820b)
Jul :: S214 systemd: Started Session of user root.
Jul :: S214 systemd: Starting Session of user root.
Jul :: S214 systemd: Started Session of user root.
这是正确的处理方式，不是去深入调查原因，也不是去hacking。
1. 升至最新版稳定内核。
2. 回退至前一版稳定内涵。
[root@S205 ~]# yum upgrade
Installing:
kernel x86_64 3.10.0-514.26.2.el7 updates 37 M
已升最新，待观察：
[root@S205 ~]# cat /etc/redhat-release
CentOS Linux release 7.3. (Core)
[root@S205 ~]# uname -a
Linux S205 3.10.-514.26..el7.x86_64 # SMP Tue Jul :: UTC x86_64 x86_64 x86_64 GNU/Linux
三：仍然重启，现象与错误信息一致。
参考：https://*.com/questions/44039958/kernel-panic-not-syncing-watchdog-detected-hard-lockup
好像是 nvidia 显卡的问题。
[root@S205 ~]# cat /etc/default/grub |grep CMDLINE
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=cl/root rd.lvm.lv=cl/swap rd.driver.blacklist=nouveau nomodeset rhgb quiet"
[root@S205 ~]#
增加内核参数：rd.driver.blacklist=nouveau nomodeset
再观察。
四：Fixed
连续24小时未重启。
完。