LVM.CONF(5)LVM.CONF(5)NAMElvm.conf - Configuration file for LVM2
SYNOPSIS
/etc/lvm/lvm.conf
DESCRIPTIONlvm.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 pro‐
vides a wide choice of acceptable indentation styles. Comments begin
with # and continue to the end of the line. They are treated as white‐
space.
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 tra‐
versed 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 any name matches any a pattern, the device is
accepted; otherwise if any name matches any 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 crypt‐
setup, 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 ’mini‐
mum_io_size’ or ’optimal_io_size’ exposed in sysfs. mini‐
mum_io_size is the smallest request the device can perform with‐
out 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 par‐
ticular device exceeds the limit set here, no further I/O is
sent to that device for the remainder of the respective opera‐
tion. Setting the parameter to 0 disables the counters alto‐
gether.
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 underly‐
ing 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 spe‐
cific 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 alloca‐
tion policy will choose space on the same PVs as the last seg‐
ment 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 out‐
put.
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 sus‐
pended during activation. Only set this temporarily while
debugging a problem because in low memory situations this set‐
ting 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. Dis‐
abling 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 cre‐
ated. 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 vol‐
umes 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 communi‐
cate with device-mapper, it will automatically invoke the equiv‐
alent 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 con‐
tain 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=inter‐
nal (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 lock‐
ing_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 liblvm2clus‐
terlock.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 subsec‐
tions. 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 configura‐
tion 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 con‐
fig 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 insuffi‐
cient memory is reserved before suspension, there is a risk of
machine deadlock.
process_priority — The nice value to use while devices are sus‐
pended. 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 log‐
ical 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.
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 suffi‐
cient, 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 hav‐
ing lots of copies is that every time the tools access the vol‐
ume 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 com‐
plex logical volume structures will need additional space for
their metadata. The metadata areas are treated as circular buf‐
fers, 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 meta‐
data areas present on newly created Physical Volumes. The
option can be overridden on the command line with --metadataig‐
nore (See pvcreate and pvchange). Metadata areas cannot be cre‐
ated 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 meta‐
data 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 meta‐
dataignore 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 meta‐
data as it may be used to minimize metadata read and write over‐
head.
dirs — List of directories holding live copies of LVM2 metadata
as text files. These directories must not be on logical vol‐
umes. 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 devel‐
opment of the LVM2 metadata before the new on-disk metadata
areas were designed and no longer gets tested. It is not sup‐
ported 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.
FILES
/etc/lvm/lvm.conf /etc/lvm/archive /etc/lvm/backup
/etc/lvm/cache/.cache /var/lock/lvm
SEE ALSOlvm(8), umask(2), uname(2), dlopen(3), syslog(3), syslog.conf(5)Sistina Software UK LVM TOOLS 2.02.88(2)-RHEL5 (2013-06-25) LVM.CONF(5)
