之前在2.6系列linux內核中，當發現某個模塊不要在保留內核中加載的時候，可以通過blacklist參數將其在/etc/kdump.conf中屏蔽
blacklist <list of kernel modules>
最近發現某個sas驅動存在問題，所以打算也這么屏蔽，結果，出錯了：
[root@localhost ~]# service kdump restart Redirecting to /bin/systemctl restart kdump.service Job for kdump.service failed because the control process exited with error code. See "systemctl status kdump.service" and "journalctl -xe" for details. [root@localhost ~]# systemctl status kdump.service * kdump.service - Crash recovery kernel arming Loaded: loaded (/usr/lib/systemd/system/kdump.service; enabled; vendor preset: enabled) Active: failed (Result: exit-code) since Tue 2017-11-28 11:58:28 UTC; 10s ago Process: 60563 ExecStop=/usr/bin/kdumpctl stop (code=exited, status=0/SUCCESS) Process: 60572 ExecStart=/usr/bin/kdumpctl start (code=exited, status=1/FAILURE) Main PID: 60572 (code=exited, status=1/FAILURE) Nov 28 11:58:28 localhost.localdomain kdumpctl[60572]: Deprecated kdump config option: blacklist. Refer to kdump.conf manpage for alternatives. Nov 28 11:58:28 localhost.localdomain kdumpctl[60572]: Starting kdump: [FAILED] Nov 28 11:58:28 localhost.localdomain systemd[1]: kdump.service: main process exited, code=exited, status=1/FAILURE Nov 28 11:58:28 localhost.localdomain systemd[1]: Failed to start Crash recovery kernel arming. Nov 28 11:58:28 localhost.localdomain systemd[1]: Unit kdump.service entered failed state. Nov 28 11:58:28 localhost.localdomain systemd[1]: kdump.service failed. [root@localhost ~]# journalctl -xe Nov 28 11:58:28 localhost.localdomain kdumpctl[60563]: kexec: unloaded kdump kernel Nov 28 11:58:28 localhost.localdomain kdumpctl[60563]: Stopping kdump: [OK] Nov 28 11:58:28 localhost.localdomain kdumpctl[60572]: Deprecated kdump config option: blacklist. Refer to kdump.conf manpage for alternatives. Nov 28 11:58:28 localhost.localdomain kdumpctl[60572]: Starting kdump: [FAILED] Nov 28 11:58:28 localhost.localdomain systemd[1]: kdump.service: main process exited, code=exited, status=1/FAILURE Nov 28 11:58:28 localhost.localdomain systemd[1]: Failed to start Crash recovery kernel arming. -- Subject: Unit kdump.service has failed -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel -- -- Unit kdump.service has failed. -- -- The result is failed. Nov 28 11:58:28 localhost.localdomain systemd[1]: Unit kdump.service entered failed state. Nov 28 11:58:28 localhost.localdomain systemd[1]: kdump.service failed. Nov 28 11:58:28 localhost.localdomain polkitd[2087]: Unregistered Authentication Agent for unix-process:60547:533046 (system bus name :1.5128, object path /org/freedesktop/PolicyKit1/AuthenticationAgent [root@localhost ~]#
發現blacklist是過時的用法了，然后參照提示：
man kdump.conf 看到如下打印：
blacklist option was recently being used to prevent loading modules in initramfs. General terminology for blacklist has been that module is present in initramfs but it is not actu- ally loaded in kernel. Hence retaining blacklist option creates more confusing behavior. It has been deprecated. Instead, use rd.driver.blacklist option on second kernel to blacklist a certain module. One can edit /etc/sysconfig/kdump.conf and edit KDUMP_COMMANDLINE_APPEND to pass kernel com- mand line options. Refer to dracut.cmdline man page for more details on module blacklist option.
好吧，按照最新的要求，打算修改/etc/sysconfig/kdump.conf，發現這個文件不存在，當然配置文件路徑不是關鍵，/etc/kdump.conf里面配置也行，
我按照manpage的提示，修改文件名是/etc/sysconfig/kdump，然后修改KDUMP_COMMANDLINE_APPEND這行命令，具體的格式參考：
man dracut.cmdline
rd.driver.blacklist=<drivername>[,<drivername>,...] do not load kernel module <drivername>. This parameter can be specified multiple times. rd.driver.pre=<drivername>[,<drivername>,...] force loading kernel module <drivername>. This parameter can be specified multiple times. rd.driver.post=<drivername>[,<drivername>,...] force loading kernel module <drivername> after all automatic loading modules have been loaded. This parameter can be specified multiple times.
另外需要注意的是，當修改了配置，就要重啟kdump服務，而這個時候，由於修改了blacklist，會導致重啟的時候比較慢，因為在涉及到配置文件變動時，如生成路徑修改或blacklist內容增加，都需要重新生成kdump的RAM文件，不然其在發生問題時還是使用老的img RAM文件，這類文件在/boot下以kdump.img結尾的文件就是：
[root@localhost ~]# ls -l /boot/*kdump* -rw------- 1 root root 16878919 Nov 29 01:02 /boot/initramfs-3.10.0-693.5.2.el7.x86_64kdump.img -rw------- 1 root root 35261890 Nov 27 07:04 /boot/initramfs-3.10.0caq1.0kdump.img -rw------- 1 root root 36508192 Nov 24 06:21 /boot/initramfs-3.10.0kdump.img [root@localhost ~]#
最后需要注意的就是，當配置的保留內核在加載驅動或者運行的時候，遇到panic，這個時候就再也沒有內核去接管它了，只能在屏幕上打印，或者接串口查看。之前遇到過保留內存不夠的
情況下，保留內核自己出現oom了，導致無法收集到crash，查看當前的保留內存可以使用：
[root@localhost ~]# cat /sys/kernel/kexec_crash_size
536870912
查看保留內核是否加載，可以使用：
[root@localhost ~]# cat /sys/kernel/kexec_crash_loaded
1