On 2016/06/02 at 15:46, Dave Young wrote:
Hi, Xunlei
Seems I sent wrong draft, here is the right one:
Add a question about below --add-driver "nfs nfsv4"
Why should we add them? if we addes dracut 95nfs module then it will install all the nfs kernel modules and network module.
Yeah, dracut 95nfs module has installkernel() { instmods nfs sunrpc ipv6 nfsv2 nfsv3 nfsv4 nfs_acl nfs_layout_nfsv41_files }
But actually during my test, I found that if nfs was not mounted, some of the modules (for example nfsv4)will fail to be installed by instmods.
But I have a concern, if the network can be setup correctly. Kdump still will find the right nic and set it up?
The implementation patch added: + dracut_args) + if is_nfs_in_dracut_args "$config_val"; then + kdump_install_net "$(get_dracut_args_target "$config_val")" + fi + ;;
So the net device when specifying nfs can be installed correctly.
On 05/27/16 at 05:39pm, Xunlei Pang wrote:
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@redhat.com Signed-off-by: Xunlei Pang xlpang@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.
Above paragraph is not necessary because it has been documented in both kdump.conf comments and manpage.
Users can utilize "dracut_args" to pass "--mount" to kdump, please refer
s/Users/One, or s/Users/You But we need keep consistently use either one or you in the following paragraph.
to "man dracut" for the format of "--mount" argument. If there is any
Dropping needless politeness: s/please refer to "man dracut" for the format of "--mount" argument/see the dracut manpage about "--mount" for details.
I found a guideline of documentation, though it is for openstack, but some general rules also fit for other documentations: http://docs.openstack.org/contributor-guide/writing-style/general-writing-gu...
This is really cool, I will have a look and modify the doc according to you valuable comments.
Regards, Xunlei
"--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".
Kdump uses "--mount" provided in dracut_args without sanity checking so you must test it and ensure the correctness. You can not use other targets in /etc/kdump.conf if you use "--mount" in dracut_args.
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"
This paragraph should be put before the usage paragraph so that it is more natrual. How about simplify it as below:
A use case of "--mount" in dracut_args is you do not want to mount dump target before kdump service startup, for example, to reduce the burden of nfs server. Such as below example: dracut_args --mount "192.168.1.1:/test /test nfs defaults"
NOTE: -Only one mount target is allowed using "dracut_args" globally.
Already mentioned above, either drop above clarification or drop this item here.
-Dracut will create <mountpoint> if it doesn't exist in kdump kernel, <mountpoint> must be specified in an absolute path.
We do not need explain the internal details, just mention about it must be 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.
Also duplicated with previous sentences above.
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
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Thanks Dave
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