Ubuntu Manpage: lvm.conf - Configuration file for LVM2

Provided by: lvm2_2.02.98-6ubuntu2_amd64

NAME

       lvm.conf - Configuration file for LVM2

SYNOPSIS

       /etc/lvm/lvm.conf

DESCRIPTION

       lvm.conf  is loaded during the initialisation phase of lvm(8).  This file can in turn lead to other files
       being loaded - settings read in later override earlier settings.  File  timestamps  are  checked  between
       commands and if any have changed, all the files are reloaded.

       Use lvm dumpconfig to check what settings are in use.

SYNTAX

       This section describes the configuration file syntax.

       Whitespace  is  not  significant  unless  it is within quotes.  This provides a wide choice of acceptable
       indentation styles.  Comments begin with # and continue to the end of the  line.   They  are  treated  as
       whitespace.

       Here is an informal grammar:

       file = value*
              A configuration file consists of a set of values.

       value = section | assignment
              A value can either be a new section, or an assignment.

       section = identifier '{' value* '}'
              A section is groups associated values together.
              It is denoted by a name and delimited by curly brackets.
              e.g. backup {
                        ...
                   }

       assignment = identifier '=' ( array | type )
              An assignment associates a type with an identifier.
              e.g. max_archives = 42

       array =  '[' ( type ',')* type ']' | '[' ']'
              Inhomogeneous arrays are supported.
              Elements must be separated by commas.
              An empty array is acceptable.

       type = integer | float | string
              integer = [0-9]*
              float = [0-9]*'.'[0-9]*
              string = '"'.*'"'

              Strings must be enclosed in double quotes.

SECTIONS

The sections that may be present in the file are:

devices — Device settings

dir — Directory in which to create volume group device nodes. Defaults to "/dev". Commands also
accept this as a prefix on volume group names.

scan — List of directories to scan recursively for LVM physical volumes. Devices in directories
outside this hierarchy will be ignored. Defaults to "/dev".

preferred_names — List of patterns compared in turn against all the pathnames referencing the same
device in in the scanned directories. The pathname that matches the earliest pattern in the list
is the one used in any output. As an example, if device-mapper multipathing is used, the
following will select multipath device names:
devices { preferred_names = [ "^/dev/mapper/mpath" ] }

filter — List of patterns to apply to devices found by a scan. Patterns are regular expressions
delimited by any character and preceded by a (for accept) or r (for reject). The list is
traversed in order, and the first regex that matches determines if the device will be accepted or
rejected (ignored). Devices that don't match any patterns are accepted. If you want to reject
patterns that don't match, end the list with "r/.*/". If there are several names for the same
device (e.g. symbolic links in /dev), if the first matching pattern in the list for any of the
names is an a pattern, the device is accepted; otherwise if the first matching pattern in the list
for any of the names is an r pattern it is rejected; otherwise it is accepted. As an example, to
ignore /dev/cdrom you could use:
devices { filter=["r|cdrom|"] }

cache_dir — Persistent filter cache file directory. Defaults to "/etc/lvm/cache".

write_cache_state — Set to 0 to disable the writing out of the persistent filter cache file when
lvm exits. Defaults to 1.

types — List of pairs of additional acceptable block device types found in /proc/devices together
with maximum (non-zero) number of partitions (normally 16). By default, LVM2 supports ide, sd,
md, loop, dasd, dac960, nbd, ida, cciss, ubd, ataraid, drbd, power2, i2o_block and iseries/vd.
Block devices with major numbers of different types are ignored by LVM2. Example: types = ["fd",
16]. To create physical volumes on device-mapper volumes created outside LVM2, perhaps encrypted
ones from cryptsetup, you'll need types = ["device-mapper", 16]. But if you do this, be careful
to avoid recursion within LVM2. The figure for number of partitions is not currently used in LVM2
- and might never be.

sysfs_scan — If set to 1 and your kernel supports sysfs and it is mounted, sysfs will be used as a
quick way of filtering out block devices that are not present.

md_component_detection — If set to 1, LVM2 will ignore devices used as components of software RAID
(md) devices by looking for md superblocks. This doesn't always work satisfactorily e.g. if a
device has been reused without wiping the md superblocks first.

md_chunk_alignment — If set to 1, and a Physical Volume is placed directly upon an md device, LVM2
will align its data blocks with the md device's stripe-width.

data_alignment_detection — If set to 1, and your kernel provides topology information in sysfs for
the Physical Volume, the start of data area will be aligned on a multiple of the ’minimum_io_size’
or ’optimal_io_size’ exposed in sysfs. minimum_io_size is the smallest request the device can
perform without incurring a read-modify-write penalty (e.g. MD's chunk size). optimal_io_size is
the device's preferred unit of receiving I/O (e.g. MD's stripe width). minimum_io_size is used if
optimal_io_size is undefined (0). If both md_chunk_alignment and data_alignment_detection are
enabled the result of data_alignment_detection is used.

data_alignment — Default alignment (in KB) of start of data area when creating a new Physical
Volume using the lvm2 format. If a Physical Volume is placed directly upon an md device and
md_chunk_alignment or data_alignment_detection is enabled this parameter is ignored. Set to 0 to
use the default alignment of 64KB or the page size, if larger.

data_alignment_offset_detection — If set to 1, and your kernel provides topology information in
sysfs for the Physical Volume, the start of the aligned data area of the Physical Volume will be
shifted by the alignment_offset exposed in sysfs.

To see the location of the first Physical Extent of an existing Physical Volume use pvs -o
+pe_start . It will be a multiple of the requested data_alignment plus the alignment_offset from
data_alignment_offset_detection (if enabled) or the pvcreate commandline.

disable_after_error_count — During each LVM operation errors received from each device are
counted. If the counter of a particular device exceeds the limit set here, no further I/O is sent
to that device for the remainder of the respective operation. Setting the parameter to 0 disables
the counters altogether.

pv_min_size — Minimal size (in KB) of the block device which can be used as a PV. In clustered
environment all nodes have to use the same value. Any value smaller than 512KB is ignored. Up to
and include version 2.02.84 the default was 512KB. From 2.02.85 onwards it was changed to 2MB to
avoid floppy drives by default.

issue_discards — Issue discards to a logical volumes's underlying physical volume(s) when the
logical volume is no longer using the physical volumes' space (e.g. lvremove, lvreduce, etc).
Discards inform the storage that a region is no longer in use. Storage that supports discards
advertise the protocol specific way discards should be issued by the kernel (TRIM, UNMAP, or WRITE
SAME with UNMAP bit set). Not all storage will support or benefit from discards but SSDs and
thinly provisioned LUNs generally do. If set to 1, discards will only be issued if both the
storage and kernel provide support.

allocation — Space allocation policies

cling_tag_list — List of PV tags matched by the cling allocation policy.

When searching for free space to extend an LV, the cling allocation policy will choose space on
the same PVs as the last segment of the existing LV. If there is insufficient space and a list of
tags is defined here, it will check whether any of them are attached to the PVs concerned and then
seek to match those PV tags between existing extents and new extents.

The @ prefix for tags is required. Use the special tag "@*" as a wildcard to match any PV tag and
so use all PV tags for this purpose.

For example, LVs are mirrored between two sites within a single VG. PVs are tagged with either
@site1 or @site2 to indicate where they are situated and these two PV tags are selected for use
with this allocation policy:

cling_tag_list = [ "@site1", "@site2" ]

log — Default log settings

file — Location of log file. If this entry is not present, no log file is written.

overwrite — Set to 1 to overwrite the log file each time a tool is invoked. By default tools
append messages to the log file.

level — Log level (0-9) of messages to write to the file. 9 is the most verbose; 0 should produce
no output.

verbose — Default level (0-3) of messages sent to stdout or stderr. 3 is the most verbose; 0
should produce the least output.

silent — Set to 1 to suppress all non-essential tool output. When set, display and reporting
tools will still write the requested device properties to standard output, but messages confirming
that something was or wasn't changed will be reduced to the 'verbose' level and not appear unless
-v is supplied.

syslog — Set to 1 (the default) to send log messages through syslog. Turn off by setting to 0.
If you set to an integer greater than one, this is used - unvalidated - as the facility. The
default is LOG_USER. See /usr/include/sys/syslog.h for safe facility values to use. For example,
LOG_LOCAL0 might be 128.

indent — When set to 1 (the default) messages are indented according to their severity, two spaces
per level. Set to 0 to turn off indentation.

command_names — When set to 1, the command name is used as a prefix for each message. Default is
0 (off).

prefix — Prefix used for all messages (after the command name). Default is two spaces.

activation — Set to 1 to log messages while devices are suspended during activation. Only set
this temporarily while debugging a problem because in low memory situations this setting can cause
your machine to lock up.

backup — Configuration for metadata backups.

archive_dir — Directory used for automatic metadata archives. Backup copies of former metadata
for each volume group are archived here. Defaults to "/etc/lvm/archive".

backup_dir — Directory used for automatic metadata backups. A single backup copy of the current
metadata for each volume group is stored here. Defaults to "/etc/lvm/backup".

archive — Whether or not tools automatically archive existing metadata into archive_dir before
making changes to it. Default is 1 (automatic archives enabled). Set to 0 to disable. Disabling
this might make metadata recovery difficult or impossible if something goes wrong.

backup — Whether or not tools make an automatic backup into backup_dir after changing metadata.
Default is 1 (automatic backups enabled). Set to 0 to disable. Disabling this might make
metadata recovery difficult or impossible if something goes wrong.

retain_min — Minimum number of archives to keep. Defaults to 10.

retain_days — Minimum number of days to keep archive files. Defaults to 30.

shell — LVM2 built-in readline shell settings

history_size — Maximum number of lines of shell history to retain (default 100) in
$HOME/.lvm_history

global — Global settings

test — If set to 1, run tools in test mode i.e. no changes to the on-disk metadata will get made.
It's equivalent to having the -t option on every command.

activation — Set to 0 to turn off all communication with the device-mapper driver. Useful if you
want to manipulate logical volumes while device-mapper is not present in your kernel.

proc — Mount point of proc filesystem. Defaults to /proc.

umask — File creation mask for any files and directories created. Interpreted as octal if the
first digit is zero. Defaults to 077. Use 022 to allow other users to read the files by default.

format — The default value of --metadatatype used to determine which format of metadata to use
when creating new physical volumes and volume groups. lvm1 or lvm2.

fallback_to_lvm1 — Set this to 1 if you need to be able to switch between 2.4 kernels using LVM1
and kernels including device-mapper. The LVM2 tools should be installed as normal and the LVM1
tools should be installed with a .lvm1 suffix e.g. vgscan.lvm1. If an LVM2 tool is then run but
unable to communicate with device-mapper, it will automatically invoke the equivalent LVM1 version
of the tool. Note that for LVM1 tools to manipulate physical volumes and volume groups created by
LVM2 you must use --metadataformat lvm1 when creating them.

library_dir — A directory searched for LVM2's shared libraries ahead of the places dlopen (3)
searches.

format_libraries — A list of shared libraries to load that contain code to process different
formats of metadata. For example, liblvm2formatpool.so is needed to read GFS pool metadata if LVM2
was configured --with-pool=shared.

locking_type — What type of locking to use. 1 is the default, which use flocks on files in
locking_dir (see below) to avoid conflicting LVM2 commands running concurrently on a single
machine. 0 disables locking and risks corrupting your metadata. If set to 2, the tools will load
the external locking_library (see below). If the tools were configured --with-cluster=internal
(the default) then 3 means to use built-in cluster-wide locking. Type 4 enforces read-only
metadata and forbids any operations that might want to modify Volume Group metadata. All changes
to logical volumes and their states are communicated using locks.

wait_for_locks — When set to 1, the default, the tools wait if a lock request cannot be satisfied
immediately. When set to 0, the operation is aborted instead.

locking_dir — The directory LVM2 places its file locks if locking_type is set to 1. The default
is /var/lock/lvm.

locking_library — The name of the external locking library to load if locking_type is set to 2.
The default is liblvm2clusterlock.so. If you need to write such a library, look at the
lib/locking source code directory.

tags — Host tag settings

hosttags — If set to 1, create a host tag with the machine name. Setting this to 0 does nothing,
neither creating nor destroying any tag. The machine name used is the nodename as returned by
uname (2).

Additional host tags to be set can be listed here as subsections. The @ prefix for tags is
optional. Each of these host tag subsections can contain a host_list array of host names. If any
one of these entries matches the machine name exactly then the host tag gets defined on this
particular host, otherwise it doesn't.

After lvm.conf has been processed, LVM2 works through each host tag that has been defined in turn,
and if there is a configuration file called lvm_<host_tag>.conf it attempts to load it. Any
settings read in override settings found in earlier files. Any additional host tags defined get
appended to the search list, so in turn they can lead to further configuration files being
processed. Use lvm dumpconfig to check the result of config file processing.

The following example always sets host tags tag1 and sets tag2 on machines fs1 and fs2:

tags { tag1 { } tag2 { host_list = [ "fs1", "fs2" ] } }

These options are useful if you are replicating configuration files around a cluster. Use of
hosttags = 1 means every machine can have static and identical local configuration files yet use
different settings and activate different logical volumes by default. See also volume_list below
and --addtag in lvm (8).

activation — Settings affecting device-mapper activation

missing_stripe_filler — When activating an incomplete logical volume in partial mode, this option
dictates how the missing data is replaced. A value of "error" will cause activation to create
error mappings for the missing data, meaning that read access to missing portions of the volume
will result in I/O errors. You can instead also use a device path, and in that case this device
will be used in place of missing stripes. However, note that using anything other than "error"
with mirrored or snapshotted volumes is likely to result in data corruption. For instructions on
how to create a device that always returns zeros, see lvcreate (8).

mirror_region_size — Unit size in KB for copy operations when mirroring.

readahead — Used when there is no readahead value stored in the volume group metadata. Set to
none to disable readahead in these circumstances or auto to use the default value chosen by the
kernel.

reserved_memory, reserved_stack — How many KB to reserve for LVM2 to use while logical volumes are
suspended. If insufficient memory is reserved before suspension, there is a risk of machine
deadlock.

process_priority — The nice value to use while devices are suspended. This is set to a high
priority so that logical volumes are suspended (with I/O generated by other processes to those
logical volumes getting queued) for the shortest possible time.

volume_list — This acts as a filter through which all requests to activate a logical volume on
this machine are passed. A logical volume is only activated if it matches an item in the list.
Tags must be preceded by @ and are checked against all tags defined in the logical volume and
volume group metadata for a match. @* is short-hand to check every tag set on the host machine
(see tags above). Logical volume and volume groups can also be included in the list by name e.g.
vg00, vg00/lvol1.

auto_activation_volume_list — This acts as a filter through which all requests to autoactivate a
logical volume on this machine are passed. A logical volume is autoactivated if it matches an item
in the list. Volumes must also pass the volume_list filter, if present. Tags must be preceded by @
and are checked against all tags defined in the logical volume and volume group metadata for a
match. @* is short-hand to check every tag set on the host machine (see tags above). Logical
volume and volume groups can also be included in the list by name e.g. vg00, vg00/lvol1.

read_only_volume_list — This acts as a filter through which all requests to activate a logical
volume on this machine are passed. A logical volume is activated in read-only mode (instead of
read-write) if it matches an item in the list. Volumes must first pass the volume_list filter, if
present. Tags must be preceded by @ and are checked against all tags defined in the logical
volume and volume group metadata for a match. @* is short-hand to check every tag set on the host
machine (see tags above). Logical volume and volume groups can also be included in the list by
name e.g. vg00, vg00/lvol1.

metadata — Advanced metadata settings

pvmetadatacopies — When creating a physical volume using the LVM2 metadata format, this is the
default number of copies of metadata to store on each physical volume. Currently it can be set to
0, 1 or 2. The default is 1. If set to 2, one copy is placed at the beginning of the disk and
the other is placed at the end. It can be overridden on the command line with --pvmetadatacopies
(see pvcreate). If creating a volume group with just one physical volume, it's a good idea to
have 2 copies. If creating a large volume group with many physical volumes, you may decide that 3
copies of the metadata is sufficient, i.e. setting it to 1 on three of the physical volumes, and 0
on the rest. Every volume group must contain at least one physical volume with at least 1 copy of
the metadata (unless using the text files described below). The disadvantage of having lots of
copies is that every time the tools access the volume group, every copy of the metadata has to be
accessed, and this slows down the tools.

pvmetadatasize — Approximate number of sectors to set aside for each copy of the metadata. Volume
groups with large numbers of physical or logical volumes, or volumes groups containing complex
logical volume structures will need additional space for their metadata. The metadata areas are
treated as circular buffers, so unused space becomes filled with an archive of the most recent
previous versions of the metadata.

pvmetadataignore When creating a physical volume using the LVM2 metadata format, this states
whether metadata areas should be ignored. The default is "n". If metadata areas on a physical
volume are ignored, LVM will not not store metadata in the metadata areas present on newly created
Physical Volumes. The option can be overridden on the command line with --metadataignore (See
pvcreate and pvchange). Metadata areas cannot be created or extended after Logical Volumes have
been allocated on the device. If you do not want to store metadata on this device, it is still
wise always to allocate a metadata area (use a non-zero value for --pvmetadatacopies) in case you
need it in the future and to use this option to instruct LVM2 to ignore it.

vgmetadatacopies — When creating a volume group using the LVM2 metadata format, this is the
default number of copies of metadata desired across all the physical volumes in the volume group.
If set to a non-zero value, LVM will automatically set or clear the metadataignore flag on the
physical volumes (see pvcreate and pvchange --metadataignore) in order to achieve the desired
number of metadata copies. An LVM command that adds or removes physical volumes (for example,
vgextend, vgreduce, vgsplit, or vgmerge), may cause LVM to automatically set or clear the
metadataignore flags. Also, if physical volumes go missing or reappear, or a new number of copies
is explicitly set (see vgchange --vgmetadatacopies), LVM may adjust the metadataignore flags. Set
vgmetadatacopies to 0 instructs LVM not to set or clear the metadataignore flags automatically.
You may set a value larger than the sum of all metadata areas on all physical volumes. The value
can be overridden on the command line with --vgmetadatacopies for various commands (for example,
vgcreate and vgchange), and can be queryied with the vg_mda_copies field of vgs. This option is
useful for volume groups containing large numbers of physical volumes with metadata as it may be
used to minimize metadata read and write overhead.

dirs — List of directories holding live copies of LVM2 metadata as text files. These directories
must not be on logical volumes. It is possible to use LVM2 with a couple of directories here,
preferably on different (non-logical-volume) filesystems and with no other on-disk metadata,
pvmetadatacopies = 0. Alternatively these directories can be in addition to the on-disk metadata
areas. This feature was created during the development of the LVM2 metadata before the new on-
disk metadata areas were designed and no longer gets tested. It is not supported under low-memory
conditions, and it is important never to edit these metadata files unless you fully understand how
things work: to make changes you should always use the tools as normal, or else vgcfgbackup, edit
backup, vgcfgrestore.

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