On 2016/05/27 at 14:39, Xunlei Pang wrote:
On 2016/05/27 at 14:00, Dave Young wrote:
> Hi, Xunlei
>
> On 05/26/16 at 09:08pm, Xunlei Pang wrote:
>> Update "kexec-kdump-howto" to illustrate the usage of special mount
>> information via "dracut_args".
>>
>> Suggested-by: Dave Young <dyoung(a)redhat.com>
>> Signed-off-by: Xunlei Pang <xlpang(a)redhat.com>
>> ---
>> kexec-kdump-howto.txt | 31 +++++++++++++++++++++++++++++++
>> 1 file changed, 31 insertions(+)
>>
>> diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt
>> index b4cdc22..f7c6811 100644
>> --- a/kexec-kdump-howto.txt
>> +++ b/kexec-kdump-howto.txt
>> @@ -345,6 +345,37 @@ mount the NFS mount and copy out the vmcore to your NFS
server. Restart the
>> kdump service via '/sbin/systemctl restart kdump.service' to commit this
change
>> to your kdump initrd.
>>
>> +Special mount via "dracut_args"
>> +
>> +Kdump uses dracut to generate initramfs for second kernel. This option
>> +allows a user to pass arguments to dracut directly.
>> +
>> +Users can utilize "dracut_args" to pass "--mount" to kdump,
please refer
>> +to "man dracut" for the format of "--mount" argument. If
there is any
>> +"--mount" specified via "dracut_args", kdump always uses it
as the final
>> +mount target without any validation(mounting or checking like mount options,
>> +fs size, save path, etc), so users are expected to ensure all the correctness.
>> +It conflicts with targets specified via "ext[234]/xfs/btrfs/nfs".
> What is the behavior for ssh dump in /etc/kdump.conf being used?
It will fail as well due to "More than one dump targets specified."
Missed ssh, I will add "ssh" here. Thanks for the catching.
>> +
>> +This is useful when we want to deploy thoundsands of diskless clients using
>> +nfs dumping and share the same nfs server. In this scenario, each time the
>> +clients are booting up, the kdump initramfs rebuild will be triggered due to
>> +the diskless environment, so all the clients will request nfs mount
simultaneouly,
>> +thereby imposing very much burdon on the shared nfs server. With the help of
>> +special mount via "dracut_args", kdump can skip mounting and resolve
the issue.
>> +Because nfs needn't to be mounted beforehand, some nfs-related ko modules
will
>> +be explicitly specified as needed together in the "dracut_args"(or via
directive
>> +"extra_modules" in /etc/kdump.conf). As an nfs mount example:
>> +dracut_args --mount "192.168.1.1:/test /test nfs defaults"
--add-driver "nfs nfsv4"
> For the stateless system use case, it is possible to avoid rebuilding during
> every boot. Ie. use a workable initrd with timestamp earlier then /etc/kdump.conf
> when admin create the rootfs etc. It is just a guess but there might be ways to
> do it. It seems not proper being used in the documentaion.
>
> How about just say that one use case is for nfs dump some admin may not want nfs
> server being mounted first.
Sure
How about the modified description below:
Special mount via "dracut_args"
Kdump uses dracut to generate initramfs for second kernel. This option
allows a user to pass arguments to dracut directly.
Users can utilize "dracut_args" to pass "--mount" to kdump, please
refer
to "man dracut" for the format of "--mount" argument. If there is any
"--mount" specified via "dracut_args", kdump always uses it as the
final
mount target without any validation(mounting or checking like mount options,
fs size, save path, etc), so users are expected to ensure all the correctness.
It conflicts with targets specified via "ext[234]/xfs/btrfs/nfs/ssh".
This is useful when administrators don't want the dump target being mounted
first. Since the dump target needn't to be mounted beforehand, some fs-related
ko modules will be explicitly specified as needed together in the "dracut_args"
(or via directive "extra_modules" in /etc/kdump.conf). As an nfs mount example:
dracut_args --mount "192.168.1.1:/test /test nfs defaults" --add-driver
"nfs nfsv4"
NOTE:
-Only one mount target is allowed using "dracut_args" globally.
-Dracut will create <mountpoint> if it doesn't exist in kdump kernel,
<mountpoint> must be specified in an absolute path.
-There must be double quotation marks behind "--mount", i.e. --mount
"<mount info>".
-Users should do a test first and ensure it works, because kdump does
not prepare the mount and check all the validity.
Regards,
Xunlei
>> +
>> +NOTE:
>> +-Only one mount target is allowed using "dracut_args" globally.
>> +-Dracut will create <mountpoint> if it doesn't exist in kdump kernel,
>> + <mountpoint> must be specified in an absolute path.
>> +-There must be double quotation marks behind "--mount", i.e. --mount
"<mount info>".
>> +-Users should do a test first and ensure it works, because kdump does
>> + not prepare the mount and check all the validity.
>> +
>> Remote system via ssh/scp
>>
>> Dumping over ssh/scp requires setting up passwordless ssh keys for every
>> --
>> 1.8.3.1
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>>
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> Thanks
> Dave
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