Re: fstab update for persistent device names
On Thu, Jul 26, 2007 at 11:40:19AM +0200, Bastian Blank wrote:
> Hi folks
>
> For the libata-pata support we need to change fstab on several arches to
> not break all systems which uses them.
Not to mention bootloader configs and other things that may handle
dump partitions.
> We need to decide which arches needs this rewrite now and which value
> should be filed in.
And also, how should we re-write them? Should we just provide
documentation, or also provide a utility to do it?
linux-images w/ libata-pata should probably detect non-persistent
names and fail to install, telling the user they need to run the
upgrade utility (or manually upgrade) before continuing.
> There are 5 or so variants:
> - /dev/disk/by-id: Includes disk serial number or wwnn.
> - /dev/disk/by-label: Filesystem label.
Do all filesystems support labels? fat doesn't, iirc.
> - /dev/disk/by-path: Includes pci device and lun.
> - /dev/disk/by-uuid: UUID of filesystem. Maybe we want the uuid of md
> devices also?
Do all filesystems support UUID?
> - LABEL=
> - UUID=
Another option is to leave the option to the user with a sane default.
I'm thinking something like:
1) scan all config files we know about that contain such references
2) Probe these devices for available persistent-names
3) Present the list of available names to the user
4) re-write all config files that reference that device
For 4), we could either try and incorporate all config file knowledge
in the utility, or provide a hook system by which we make a name map
available but each package is responsible for doing its own
renaming. The latter would give us a pass on the "don't edit other
package's config files" rule.
> We have to support the following device types, I think:
> - pata, sata, parallel scsi, sas
> No problem, I would prefer by-id. It should be stable for this types
> of devices. So a user needs to fix this entry for a disk replacement.
> - fiberchannel
> by-id. It includes the wwnn, which is defined as unique for each
> device. If someone have more than one path to the disk, they need
> multipath-tools anyway, which creates /dev/mapper/$wwnn.
> - iscsi
> This is a problem. iscsi have a stable identifier for a device, but it
> is not exported by udev. udev provides the following:
> | /dev/disk/by-id/scsi-16465616462656166333a3100000000000000000000000000
> This is the usual disc identification. And:
> | /dev/disk/by-path/ip-192.168.9.13:3260-iscsi-iqn.2007-07.org.zseries.debian00:storage.org.zseries.debian04v4-lun-1
> This includes the ip of the target, the id and the lun. The id is
> defined to be unique for a device.
> Maybe we want something like
> by-id/iscsi-iqn.2007-07.org.zseries.debian00:storage.org.zseries.debian04v4-lun-1.
> More than one path needs multipath-tools also.
>
> The following devices can be ignored:
> - md*
> - mapper/*
> - lvm symlinks
>
> Or should we ignore all devices which we don't know about?
I would think so.
--
dann frazier
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