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lvm2/tools/commands.h
David Teigland 83fe6e720f device usage based on devices file 
The LVM devices file lists devices that lvm can use.  The default
file is /etc/lvm/devices/system.devices, and the lvmdevices(8)
command is used to add or remove device entries.  If the file
does not exist, or if lvm.conf includes use_devicesfile=0, then
lvm will not use a devices file.  When the devices file is in use,
the regex filter is not used, and the filter settings in lvm.conf
or on the command line are ignored.

LVM records devices in the devices file using hardware-specific
IDs, such as the WWID, and attempts to use subsystem-specific
IDs for virtual device types.  These device IDs are also written
in the VG metadata.  When no hardware or virtual ID is available,
lvm falls back using the unstable device name as the device ID.
When devnames are used, lvm performs extra scanning to find
devices if their devname changes, e.g. after reboot.

When proper device IDs are used, an lvm command will not look
at devices outside the devices file, but when devnames are used
as a fallback, lvm will scan devices outside the devices file
to locate PVs on renamed devices.  A config setting
search_for_devnames can be used to control the scanning for
renamed devname entries.

Related to the devices file, the new command option
--devices <devnames> allows a list of devices to be specified for
the command to use, overriding the devices file.  The listed
devices act as a sort of devices file in terms of limiting which
devices lvm will see and use.  Devices that are not listed will
appear to be missing to the lvm command.

Multiple devices files can be kept in /etc/lvm/devices, which
allows lvm to be used with different sets of devices, e.g.
system devices do not need to be exposed to a specific application,
and the application can use lvm on its own set of devices that are
not exposed to the system.  The option --devicesfile <filename> is
used to select the devices file to use with the command.  Without
the option set, the default system devices file is used.

Setting --devicesfile "" causes lvm to not use a devices file.

An existing, empty devices file means lvm will see no devices.

The new command vgimportdevices adds PVs from a VG to the devices
file and updates the VG metadata to include the device IDs.
vgimportdevices -a will import all VGs into the system devices file.

LVM commands run by dmeventd not use a devices file by default,
and will look at all devices on the system.  A devices file can
be created for dmeventd (/etc/lvm/devices/dmeventd.devices)  If
this file exists, lvm commands run by dmeventd will use it.

Internal implementaion:

- device_ids_read - read the devices file
  . add struct dev_use (du) to cmd->use_devices for each devices file entry
- dev_cache_scan - get /dev entries
  . add struct device (dev) to dev_cache for each device on the system
- device_ids_match - match devices file entries to /dev entries
  . match each du on cmd->use_devices to a dev in dev_cache, using device ID
  . on match, set du->dev, dev->id, dev->flags MATCHED_USE_ID
- label_scan - read lvm headers and metadata from devices
  . filters are applied, those that do not need data from the device
  . filter-deviceid skips devs without MATCHED_USE_ID, i.e.
    skips /dev entries that are not listed in the devices file
  . read lvm label from dev
  . filters are applied, those that use data from the device
  . read lvm metadata from dev
  . add info/vginfo structs for PVs/VGs (info is "lvmcache")
- device_ids_find_renamed_devs - handle devices with unstable devname ID
  where devname changed
  . this step only needed when devs do not have proper device IDs,
    and their dev names change, e.g. after reboot sdb becomes sdc.
  . detect incorrect match because PVID in the devices file entry
    does not match the PVID found when the device was read above
  . undo incorrect match between du and dev above
  . search system devices for new location of PVID
  . update devices file with new devnames for PVIDs on renamed devices
  . label_scan the renamed devs
- continue with command processing
2021-02-23 16:43:32 -06:00

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/*
* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2014 Red Hat, Inc. All rights reserved.
*
* This file is part of LVM2.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU Lesser General Public License v.2.1.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
xx(config,
"Display and manipulate configuration information",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(devtypes,
"Display recognised built-in block device types",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(dumpconfig,
"Display and manipulate configuration information",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(formats,
"List available metadata formats",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(help,
"Display help for commands",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(fullreport,
"Display full report",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | ALLOW_HINTS | ALLOW_EXPORTED)
xx(lastlog,
"Display last command's log report",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(lvchange,
"Change the attributes of logical volume(s)",
PERMITTED_READ_ONLY | ALLOW_HINTS)
xx(lvconvert,
"Change logical volume layout",
GET_VGNAME_FROM_OPTIONS)
xx(lvcreate,
"Create a logical volume",
ALLOW_HINTS)
xx(lvdisplay,
"Display information about a logical volume",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | CAN_USE_ONE_SCAN | ALLOW_HINTS)
xx(lvextend,
"Add space to a logical volume",
ALLOW_HINTS)
xx(lvmchange,
"With the device mapper, this is obsolete and does nothing.",
0)
xx(lvmconfig,
"Display and manipulate configuration information",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(lvmdevices,
"Manage the devices file",
0)
xx(lvmdiskscan,
"List devices that may be used as physical volumes",
PERMITTED_READ_ONLY | ENABLE_ALL_DEVS | ALLOW_EXPORTED)
xx(lvmsadc,
"Collect activity data",
0)
xx(lvmsar,
"Create activity report",
0)
xx(lvreduce,
"Reduce the size of a logical volume",
ALLOW_HINTS)
xx(lvremove,
"Remove logical volume(s) from the system",
ALL_VGS_IS_DEFAULT | ALLOW_HINTS) /* all VGs only with --select */
xx(lvrename,
"Rename a logical volume",
ALLOW_HINTS)
xx(lvresize,
"Resize a logical volume",
ALLOW_HINTS)
xx(lvs,
"Display information about logical volumes",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | CAN_USE_ONE_SCAN | ALLOW_HINTS)
xx(lvscan,
"List all logical volumes in all volume groups",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(pvchange,
"Change attributes of physical volume(s)",
0)
xx(pvresize,
"Resize physical volume(s)",
0)
xx(pvck,
"Check metadata on physical volumes",
LOCKD_VG_SH | ALLOW_EXPORTED)
xx(pvcreate,
"Initialize physical volume(s) for use by LVM",
ENABLE_ALL_DEVS)
xx(pvdata,
"Display the on-disk metadata for physical volume(s)",
0)
xx(pvdisplay,
"Display various attributes of physical volume(s)",
PERMITTED_READ_ONLY | ENABLE_ALL_DEVS | ENABLE_DUPLICATE_DEVS | LOCKD_VG_SH | CAN_USE_ONE_SCAN | ALLOW_HINTS | ALLOW_EXPORTED)
/* ALL_VGS_IS_DEFAULT is for polldaemon to find pvmoves in-progress using process_each_vg. */
xx(pvmove,
"Move extents from one physical volume to another",
ALL_VGS_IS_DEFAULT | DISALLOW_TAG_ARGS)
xx(lvpoll,
"Continue already initiated poll operation on a logical volume",
0)
xx(pvremove,
"Remove LVM label(s) from physical volume(s)",
ENABLE_ALL_DEVS)
xx(pvs,
"Display information about physical volumes",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | ENABLE_ALL_DEVS | ENABLE_DUPLICATE_DEVS | LOCKD_VG_SH | CAN_USE_ONE_SCAN | ALLOW_HINTS | ALLOW_EXPORTED)
xx(pvscan,
"List all physical volumes",
PERMITTED_READ_ONLY | LOCKD_VG_SH | ALLOW_EXPORTED)
xx(segtypes,
"List available segment types",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(systemid,
"Display the system ID, if any, currently set on this host",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(tags,
"List tags defined on this host",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(vgcfgbackup,
"Backup volume group configuration(s)",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | ALLOW_EXPORTED)
xx(vgcfgrestore,
"Restore volume group configuration",
ALLOW_EXPORTED)
xx(vgchange,
"Change volume group attributes",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | ALLOW_HINTS)
xx(vgck,
"Check the consistency of volume group(s)",
ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(vgconvert,
"Change volume group metadata format",
0)
xx(vgcreate,
"Create a volume group",
MUST_USE_ALL_ARGS | ENABLE_ALL_DEVS)
xx(vgdisplay,
"Display volume group information",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | CAN_USE_ONE_SCAN | ALLOW_HINTS | ALLOW_EXPORTED)
xx(vgexport,
"Unregister volume group(s) from the system",
ALL_VGS_IS_DEFAULT)
xx(vgextend,
"Add physical volumes to a volume group",
MUST_USE_ALL_ARGS | ENABLE_ALL_DEVS)
xx(vgimport,
"Register exported volume group with system",
ALL_VGS_IS_DEFAULT | ALLOW_EXPORTED)
xx(vgimportclone,
"Import a VG from cloned PVs",
ALLOW_EXPORTED)
xx(vgimportdevices,
"Add devices for a VG to the devices file.",
ALL_VGS_IS_DEFAULT | ALLOW_EXPORTED)
xx(vgmerge,
"Merge volume groups",
0)
xx(vgmknodes,
"Create the special files for volume group devices in /dev",
ALL_VGS_IS_DEFAULT)
xx(vgreduce,
"Remove physical volume(s) from a volume group",
0)
xx(vgremove,
"Remove volume group(s)",
ALL_VGS_IS_DEFAULT) /* all VGs only with select */
xx(vgrename,
"Rename a volume group",
ALLOW_UUID_AS_NAME | ALLOW_EXPORTED)
xx(vgs,
"Display information about volume groups",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | CAN_USE_ONE_SCAN | ALLOW_HINTS | ALLOW_EXPORTED)
xx(vgscan,
"Search for all volume groups",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | ALLOW_EXPORTED)
xx(vgsplit,
"Move physical volumes into a new or existing volume group",
0)
xx(version,
"Display software and driver version information",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
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