lvm2/man/lvm.8.in

.TH LVM 8 "LVM TOOLS #VERSION#" "Sistina Software UK" \" -*- nroff -*-
.SH NAME
lvm \- LVM2 tools
.SH SYNOPSIS
.B lvm
[command | file]
.SH DESCRIPTION
lvm provides the command-line tools for LVM2.  A separate
manual page describes each command in detail.
.LP
If \fBlvm\fP is invoked with no arguments it presents a readline prompt
(assuming it was compiled with readline support).
LVM commands may be entered interactively at this prompt with
readline facilities including history and command name and option
completion.  Refer to \fBreadline\fP(3) for details.
.LP
If \fBlvm\fP is invoked with argv[0] set to the name of a specific
LVM command (for example by using a hard or soft link) it acts as
that command.
.LP
On invocation, \fBlvm\fP requires that only the standard file descriptors
stdin, stdout and stderr are available.  If others are found, they
get closed and messages are issued warning about the leak.
This warning can be suppressed by setting the environment variable
.B LVM_SUPPRESS_FD_WARNINGS\fP.
.LP
Where commands take VG or LV names as arguments, the full path name is
optional.  An LV called "lvol0" in a VG called "vg0" can be specified
as "vg0/lvol0".  Where a list of VGs is required but is left empty,
a list of all VGs will be substituted.  Where a list of LVs is required
but a VG is given, a list of all the LVs in that VG will be substituted.
So \fBlvdisplay vg0\fP will display all the LVs in "vg0".
Tags can also be used - see \fB\-\-addtag\fP below.
.LP
One advantage of using the built-in shell is that configuration
information gets cached internally between commands.
.LP
A file containing a simple script with one command per line
can also be given on the command line.  The script can also be
executed directly if the first line is #! followed by the absolute
path of \fBlvm\fP.
.SH BUILT-IN COMMANDS
The following commands are built into lvm without links normally
being created in the filesystem for them.
.TP
\fBdumpconfig\fP \(em Display the configuration information after
loading \fBlvm.conf\fP(5) and any other configuration files.
.TP
\fBdevtypes\fP \(em Display the recognised built-in block device types.
.TP
\fBformats\fP \(em Display recognised metadata formats.
.TP
\fBhelp\fP \(em Display the help text.
.TP
\fBpvdata\fP \(em Not implemented in LVM2.
.TP
\fBsegtypes\fP \(em Display recognised Logical Volume segment types.
.TP
\fBtags\fP \(em Display any tags defined on this host.
.TP
\fBversion\fP \(em Display version information.
.LP
.SH COMMANDS
The following commands implement the core LVM functionality.
.TP
\fBpvchange\fP \(em Change attributes of a Physical Volume.
.TP
\fBpvck\fP \(em Check Physical Volume metadata.
.TP
\fBpvcreate\fP \(em Initialize a disk or partition for use by LVM.
.TP
\fBpvdisplay\fP \(em Display attributes of a Physical Volume.
.TP
\fBpvmove\fP \(em Move Physical Extents.
.TP
\fBpvremove\fP \(em Remove a Physical Volume.
.TP
\fBpvresize\fP \(em Resize a disk or partition in use by LVM2.
.TP
\fBpvs\fP \(em Report information about Physical Volumes.
.TP
\fBpvscan\fP \(em Scan all disks for Physical Volumes.
.TP
\fBvgcfgbackup\fP \(em Backup Volume Group descriptor area.
.TP
\fBvgcfgrestore\fP \(em Restore Volume Group descriptor area.
.TP
\fBvgchange\fP \(em Change attributes of a Volume Group.
.TP
\fBvgck\fP \(em Check Volume Group metadata.
.TP
\fBvgconvert\fP \(em Convert Volume Group metadata format.
.TP
\fBvgcreate\fP \(em Create a Volume Group.
.TP
\fBvgdisplay\fP \(em Display attributes of Volume Groups.
.TP
\fBvgexport\fP \(em Make volume Groups unknown to the system.
.TP
\fBvgextend\fP \(em Add Physical Volumes to a Volume Group.
.TP
\fBvgimport\fP \(em Make exported Volume Groups known to the system.
.TP
\fBvgimportclone\fP \(em Import and rename duplicated Volume Group (e.g. a hardware snapshot).
.TP
\fBvgmerge\fP \(em Merge two Volume Groups.
.TP
\fBvgmknodes\fP \(em Recreate Volume Group directory and Logical Volume special files
.TP
\fBvgreduce\fP \(em Reduce a Volume Group by removing one or more
Physical Volumes.
.TP
\fBvgremove\fP \(em Remove a Volume Group.
.TP
\fBvgrename\fP \(em Rename a Volume Group.
.TP
\fBvgs\fP \(em Report information about Volume Groups.
.TP
\fBvgscan\fP \(em Scan all disks for Volume Groups and rebuild caches.
.TP
\fBvgsplit\fP \(em Split a Volume Group into two, moving any logical
volumes from one Volume Group to another by moving entire Physical
Volumes.
.TP
\fBlvchange\fP \(em Change attributes of a Logical Volume.
.TP
\fBlvconvert\fP \(em Convert a Logical Volume from linear to mirror or snapshot.
.TP
\fBlvcreate\fP \(em Create a Logical Volume in an existing Volume Group.
.TP
\fBlvdisplay\fP \(em Display attributes of a Logical Volume.
.TP
\fBlvextend\fP \(em Extend the size of a Logical Volume.
.TP
\fBlvmchange\fP \(em Change attributes of the Logical Volume Manager.
.TP
\fBlvmdiskscan\fP \(em Scan for all devices visible to LVM2.
.TP
\fBlvmdump\fP \(em Create lvm2 information dumps for diagnostic purposes.
.TP
\fBlvreduce\fP \(em Reduce the size of a Logical Volume.
.TP
\fBlvremove\fP \(em Remove a Logical Volume.
.TP
\fBlvrename\fP \(em Rename a Logical Volume.
.TP
\fBlvresize\fP \(em Resize a Logical Volume.
.TP
\fBlvs\fP \(em Report information about Logical Volumes.
.TP
\fBlvscan\fP \(em Scan (all disks) for Logical Volumes.
.TP
The following commands are not implemented in LVM2 but might be in the future: lvmsadc, lvmsar, pvdata.
.SH OPTIONS
The following options are available for many of the commands.
They are implemented generically and documented here rather
than repeated on individual manual pages.
.TP
.BR \-h ", " \-? ", " \-\-help
Display the help text.
.TP
.B \-\-version
Display version information.
.TP
.BR \-v ", " \-\-verbose
Set verbose level. Repeat from 1 to 3 times to increase the detail
of messages sent to stdout and stderr.  Overrides config file setting.
.TP
.BR \-d ", " \-\-debug
Set debug level. Repeat from 1 to 6 times to increase the detail of
messages sent to the log file and/or syslog (if configured).
Overrides config file setting.
.TP
.BR \-q ", "  \-\-quiet
Suppress output and log messages.
Overrides \fB\-d\fP and \fB\-v\fP.
.TP
.BR \-\-yes
Don't prompt for confirmation interactively but instead always assume the
answer is 'yes'.  Take great care if you use this!
.TP
.BR \-t ", " \-\-test
Run in test mode. Commands will not update metadata.
This is implemented by disabling all metadata writing but nevertheless
returning success to the calling function.  This may lead to unusual
error messages in multi-stage operations if a tool relies on reading
back metadata it believes has changed but hasn't.
.TP
.BR \-\-driverloaded " {" \fIy | \fIn }
Whether or not the device-mapper kernel driver is loaded.
If you set this to \fIn\fP, no attempt will be made to contact the driver.
.TP
.BR \-A ", " \-\-autobackup " {" \fIy | \fIn }
Whether or not to metadata should be backed up automatically after a change.
You are strongly advised not to disable this!
See \fBvgcfgbackup\fP(8).
.TP
.BR \-P ", " \-\-partial
When set, the tools will do their best to provide access to Volume Groups
that are only partially available (one or more Physical Volumes belonging
to the Volume Group are missing from the system).  Where part of a logical
volume is missing, \fB/dev/ioerror\fP will be substituted, and you could use
\fBdmsetup\fP(8) to set this up to return I/O errors when accessed,
or create it as a large block device of nulls.  Metadata may not be
changed with this option. To insert a replacement Physical Volume
of the same or large size use \fBpvcreate \-u\fP to set the uuid to
match the original followed by \fBvgcfgrestore\fP(8).
.TP
.BR \-M ", " \-\-metadatatype " " \fIType
Specifies which type of on-disk metadata to use, such as \fIlvm1\fP
or \fIlvm2\fP, which can be abbreviated to \fI1\fP or \fI2\fP respectively.
The default (\fIlvm2\fP) can be changed by setting \fBformat\fP
in the \fBglobal\fP section of the config file.
.TP
.B \-\-ignorelockingfailure
This lets you proceed with read-only metadata operations such as
\fBlvchange \-ay\fP and \fBvgchange \-ay\fP even if the locking module fails.
One use for this is in a system init script if the lock directory
is mounted read-only when the script runs.
.TP
.B \-\-ignoreskippedcluster
Use to avoid exiting with an non-zero status code if the command is run
without clustered locking and some clustered Volume Groups have to be
skipped over.
.TP
.B \-\-addtag \fITag
Add the tag \fITag\fP to a PV, VG or LV.
Supply this argument multiple times to add more than one tag at once.
A tag is a word that can be used to group LVM2 objects of the same type
together.
Tags can be given on the command line in place of PV, VG or LV
arguments.  Tags should be prefixed with @ to avoid ambiguity.
Each tag is expanded by replacing it with all objects possessing
that tag which are of the type expected by its position on the command line.
PVs can only possess tags while they are part of a Volume Group:
PV tags are discarded if the PV is removed from the VG.
As an example, you could tag some LVs as \fBdatabase\fP and others
as \fBuserdata\fP and then activate the database ones
with \fBlvchange \-ay @database\fP.
Objects can possess multiple tags simultaneously.
Only the new LVM2 metadata format supports tagging: objects using the
LVM1 metadata format cannot be tagged because the on-disk format does not
support it.
Characters allowed in tags are:
.B A-Z a-z 0-9 _ + . -
and as of version 2.02.78 the following characters are also accepted:
.B / = ! : # &
.TP
.B \-\-deltag \fITag
Delete the tag \fITag\fP from a PV, VG or LV, if it's present.
Supply this argument multiple times to remove more than one tag at once.
.TP
.IR \fB\-\-alloc \ { anywhere | contiguous | cling | inherit | normal }
Selects the allocation policy when a command needs to allocate
Physical Extents from the Volume Group.
Each Volume Group and Logical Volume has an allocation policy defined.
The default for a Volume Group is \fInormal\fP which applies
common-sense rules such as not placing parallel stripes on the same
Physical Volume.  The default for a Logical Volume is \fIinherit\fP
which applies the same policy as for the Volume Group.  These policies can
be changed using \fBlvchange\fP(8) and \fBvgchange\fP(8) or overridden
on the command line of any command that performs allocation.
The \fIcontiguous\fP policy requires that new Physical Extents be placed adjacent
to existing Physical Extents.
The \fIcling\fP policy places new Physical Extents on the same Physical
Volume as existing Physical Extents in the same stripe of the Logical Volume.
If there are sufficient free Physical Extents to satisfy
an allocation request but \fInormal\fP doesn't use them,
\fIanywhere\fP will - even if that reduces performance by
placing two stripes on the same Physical Volume.
.TP
.IR \fB\-\-profile \ ProfileName
Selects the configuration profile to use when processing an LVM command.
In addition to that, when creating a Volume Group or a Logical Volume,
it causes the ProfileName to be stored in metadata for each Volume Group
or Logical Volume. If the profile is stored in metadata, it is automatically
applied next time the Volume Group or the Logical Volume is processed and the
use of --profile is not necessary when running LVM commands further. See also
\fBlvm.conf\fP(5) for more information about \fBprofile config\fP and the
way it fits with other LVM configuration methods.
.TP
.IR \fB\-\-config \ ConfigurationString
Uses the ConfigurationString as direct string representation of the configuration
to override the existing configuration. The ConfigurationString is of exactly
the same format as used in any LVM configuration file. See \fBlvm.conf\fP(5)
for more information about \fBdirect config override on command line\fP and the
way it fits with other LVM configuration methods.
.SH ENVIRONMENT VARIABLES
.TP
.B HOME
Directory containing \fI.lvm_history\fP if the internal readline
shell is invoked.
.TP
.B LVM_SYSTEM_DIR
Directory containing \fBlvm.conf\fP(5) and other LVM system files.
Defaults to "#DEFAULT_SYS_DIR#".
.TP
.B LVM_SUPPRESS_FD_WARNINGS
Suppress warnings about openned file descriptors, when lvm command
is executed.
.TP
.B LVM_VG_NAME
The Volume Group name that is assumed for
any reference to a Logical Volume that doesn't specify a path.
Not set by default.
.TP
.B LVM_LVMETAD_PIDFILE
Path for the lvmetad pid file.
.TP
.B LVM_LVMETAD_SOCKET
Path for the lvmetad socket file.
.SH VALID NAMES
The following characters are valid for VG and LV names:
.B a-z A-Z 0-9 + _ . -
.LP
VG and LV names cannot begin with a hyphen.
There are also various reserved names that are used internally by lvm that can not be used as LV or VG names.
A VG cannot be called anything that exists in /dev/ at the time of creation, nor can it be called '.' or '..'.
A LV cannot be called '.' '..' 'snapshot' or 'pvmove'. The LV name may also not contain
the strings '_mlog', '_mimage', '_rimage', '_tdata', '_tmeta'.
.SH ALLOCATION
When an operation needs to allocate Physical Extents for one or more
Logical Volumes, the tools proceed as follows:

First of all, they generate the complete set of unallocated Physical Extents
in the Volume Group.  If any ranges of Physical Extents are supplied at
the end of the command line, only unallocated Physical Extents within
those ranges on the specified Physical Volumes are considered.

Then they try each allocation policy in turn, starting with the strictest
policy (\fIcontiguous\fP) and ending with the allocation policy specified
using \fB\-\-alloc\fP or set as the default for the particular Logical
Volume or Volume Group concerned.  For each policy, working from the
lowest-numbered Logical Extent of the empty Logical Volume space that
needs to be filled, they allocate as much space as possible according to
the restrictions imposed by the policy.  If more space is needed,
they move on to the next policy.

The restrictions are as follows:

\fIContiguous\fP requires that the physical location of any Logical
Extent that is not the first Logical Extent of a Logical Volume is
adjacent to the physical location of the Logical Extent immediately
preceding it.

\fICling\fP requires that the Physical Volume used for any Logical
Extent to be added to an existing Logical Volume is already in use by at
least one Logical Extent earlier in that Logical Volume.  If the
configuration parameter allocation/cling_tag_list is defined, then two
Physical Volumes are considered to match if any of the listed tags is
present on both Physical Volumes.  This allows groups of Physical
Volumes with similar properties (such as their physical location) to be
tagged and treated as equivalent for allocation purposes.

When a Logical Volume is striped or mirrored, the above restrictions are
applied independently to each stripe or mirror image (leg) that needs
space.

\fINormal\fP will not choose a Physical Extent that shares the same Physical
Volume as a Logical Extent already allocated to a parallel Logical
Volume (i.e. a different stripe or mirror image/leg) at the same offset 
within that parallel Logical Volume.

When allocating a mirror log at the same time as Logical Volumes to hold
the mirror data, Normal will first try to select different Physical
Volumes for the log and the data.  If that's not possible and the
allocation/mirror_logs_require_separate_pvs configuration parameter is
set to 0, it will then allow the log to share Physical Volume(s) with
part of the data.  

When allocating thin pool metadata, similar considerations to those of a
mirror log in the last paragraph apply based on the value of the
allocation/thin_pool_metadata_require_separate_pvs configuration
parameter.

If you rely upon any layout behaviour beyond that documented here, be
aware that it might change in future versions of the code.  

For example, if you supply on the command line two empty Physical
Volumes that have an identical number of free Physical Extents available for
allocation, the current code considers using each of them in the order
they are listed, but there is no guarantee that future releases will
maintain that property.  If it is important to obtain a specific layout
for a particular Logical Volume, then you should build it up through a
sequence of \fBlvcreate\fP(8) and \fBlvconvert\fP(8) steps such that the
restrictions described above applied to each step leave the tools no
discretion over the layout.

To view the way the allocation process currently works in any specific
case, read the debug logging output, for example by adding \fB\-vvvv\fP to
a command.

.SH LOGICAL VOLUME TYPES
Some logical volume types are simple to create and can be done with a
single \fBlvcreate\fP(8) command.  The linear and striped logical
volume types are an example of this.  Other logical volume types may
require more than one command to create.  The cache and thin provisioning
types are examples of this.

.br
.SS Cache
The \fIcache\fP logical volume type uses a small and fast LV to improve
the performance of a large and slow LV.  It does this by storing the
frequently used blocks on the faster LV.
LVM refers to the small fast LV as a \fBcache pool LV\fP.  The large
slow LV is called the \fBorigin LV\fP.  Due to requirements from dm-cache
(the kernel driver), LVM further splits the cache pool LV into two
devices - the \fBcache data LV\fP and \fBcache metadata LV\fP.  The cache
data LV is where copies of data blocks are kept from the
origin LV to increase speed.  The cache metadata LV holds the
accounting information that specifies where data blocks are stored (e.g.
on the origin LV or on the cache data LV).  Users should be familiar with
these LVs if they wish to create the best and most robust cached
logical volumes.

.SS Cache Terms
.nf
origin LV           OriginLV      large slow LV
cache data LV       CacheDataLV   small fast LV for cache pool data
cache metadata LV   CacheMetaLV   small fast LV for cache pool metadata
cache pool LV       CachePoolLV   CacheDataLV + CacheMetaLV
cache LV            CacheLV       OriginLV + CachePoolLV
.fi

.SS Cache Steps
The steps to create a logical volume of \fIcache\fP type are as follows:
.TP
0.
Create an LV or identify an existing LV to be the origin LV.
.TP
1.
Create the cache data LV.  The size of this LV is the size of the cache
and will be reported as the size of the cache pool LV.
.TP
2.
Create the cache metadata LV.
The size of this LV should be 1000 times smaller than the cache data LV
with a minimum size of 8MiB.
.TP
3.
Create the cache pool LV by combining the cache data LV (from step 1)
and cache metadata LV (from step 2).  When performing this step,
behavioral characteristics of the cache pool LV can be set.
The name of the cache pool LV takes the name of the cache data LV and
the cache data LV and cache metadata LV are renamed
to CachePoolLV_cdata and CachePoolLV_cmeta.
.TP
4.
Create a cache LV by linking the cache pool LV to the origin LV.
The user accessible cache LV takes the name of the origin LV,
while the origin LV becomes a hidden LV with the name
OriginLV_corig.  Users can perform this step while the origin LV
is in use.

.P
The steps above represent the best way to create a cache LV.
They provide the most options and have the ability to create the
most robust logical volumes.  The examples below illustrate how these
steps might be used in practice.

.SS Cache Commands
.nf
0. create OriginLV
lvcreate -L LargeSize -n OriginLV VG SlowPVs

1. create CacheDataLV
lvcreate -L CacheSize -n CacheDataLV VG FastPVs

2. create CacheMetaLV
lvcreate -L MetaSize -n CacheMetaLV VG FastPVs

3. create CachePoolLV
lvconvert --type cache-pool --poolmetadata VG/CacheMetaLV VG/CacheDataLV
CachePoolLV takes the name of CacheDataLV.
CacheDataLV is renamed CachePoolLV_cdata and becomes hidden.
CacheMetaLV is renamed CachePoolLV_cmeta and becomes hidden.

4. create CacheLV
lvconvert --type cache --cachepool VG/CachePoolLV VG/OriginLV
CacheLV takes the name of OriginLV.
OriginLV is renamed OriginLV_corig and becomes hidden.
.fi

.SS Cache Examples

.B Example 1:
Creating a simple cache LV.
.br

.nf
0. Create the origin LV
# lvcreate -L 10G -n lvx vg /dev/slow_dev

1. Create a cache data LV
# lvcreate -L 1G -n lvx_cache vg /dev/fast_dev

2. Create a cache metadata LV (~1/1000th size of CacheDataLV or 8MiB)
# lvcreate -L 8M -n lvx_cache_meta vg /dev/fast_dev

3. Create a cache pool LV, combining cache data LV and cache metadata LV
# lvconvert --type cache-pool --poolmetadata vg/lvx_cache_meta \\
	vg/lvx_cache

4. Create a cached LV by combining the cache pool LV and origin LV
# lvconvert --type cache --cachepool vg/lvx_cache vg/lvx
.fi

.B Example 2:
Creating a cache LV with a fault tolerant cache pool LV.

Users who are concerned about the possibility of failures in their fast devices
that could lead to data loss might consider making their cache pool sub-LVs
redundant.  Example 2 illustrates how to do that.  Note that only steps
1 & 2 change.

.nf
0. Create an origin LV we wish to cache
# lvcreate -L 10G -n lvx vg /dev/slow_devs

1. Create a 2-way RAID1 cache data LV
# lvcreate --type raid1 -m 1 -L 1G -n lvx_cache vg \\
	/dev/fast1 /dev/fast2

2. Create a 2-way RAID1 cache metadata LV
# lvcreate --type raid1 -m 1 -L 8M -n lvx_cache_meta vg \\
	/dev/fast1 /dev/fast2

3. Create a cache pool LV combining cache data LV and cache metadata LV
# lvconvert --type cache-pool --poolmetadata vg/lvx_cache_meta \\
	vg/lvx_cache

4. Create a cached LV by combining the cache pool LV and origin LV
# lvconvert --type cache --cachepool vg/lvx_cache vg/lvx
.fi

.B Example 3:
Creating a simple cache LV with \fIwritethough\fP caching.

Some users wish to ensure that any data written will be stored both in the
cache pool LV and on the origin LV.  The loss of a device associated with
the cache pool LV in this case would not mean the loss of any data.  When
combining the cache data LV and the cache metadata LV to form the cache pool
LV, properties of the cache can be specified - in this case,
\fIwritethrough\fP vs. \fIwriteback\fP.  Note that only step 3 is affected
in this case.

.nf
0. Create an origin LV we wish to cache (yours may already exist)
# lvcreate -L 10G -n lvx vg /dev/slow

1. Create a cache data LV
# lvcreate -L 1G -n lvx_cache vg /dev/fast

2. Create a cache metadata LV
# lvcreate -L 8M -n lvx_cache_meta vg /dev/fast

3. Create a cache pool LV specifying cache mode "writethrough"
# lvconvert --type cache-pool --poolmetadata vg/lvx_cache_meta \\
	--cachemode writethrough vg/lvx_cache

4. Create a cache LV by combining the cache pool LV and origin LV
# lvconvert --type cache --cachepool vg/lvx_cache vg/lvx
.fi

.SS Removing Cache Logical Volumes
If you wish to remove all logical volumes associated with a cache
LV, you must remove both top-level, user-visible devices.
The cache metadata LV and cache data LV cannot be removed
directly.  If only the cache pool LV is specfied for removal, any cached
blocks not yet on the origin LV will be flush, the cache pool LV will be
removed, and the now un-cached origin LV will remain.  If the user
specifies a cache LV for removal, then the origin LV is
removed and only the cache pool LV will remain.  The cache pool LV can then
be used to create another cache LV with a different origin LV if desired.

When users intend to remove all logical volumes associated with a
cache LV, it is generally better to start with the origin LV and then
remove the cache pool LV.  If the operations are performed in the
reverse order, the user will have to wait for the contents of the
cache pool LV to be flushed before the origin LV is removed.  This
could take some time.

.SH DIAGNOSTICS
All tools return a status code of zero on success or non-zero on failure.
.SH FILES
.I #DEFAULT_SYS_DIR#/lvm.conf
.br
.I $HOME/.lvm_history
.SH SEE ALSO
.BR lvm.conf (5),
.BR clvmd (8),
.BR lvchange (8),
.BR lvcreate (8),
.BR lvdisplay (8),
.BR lvextend (8),
.BR lvmchange (8),
.BR lvmdiskscan (8),
.BR lvreduce (8),
.BR lvremove (8),
.BR lvrename (8),
.BR lvresize (8),
.BR lvs (8),
.BR lvscan (8),
.BR pvchange (8),
.BR pvck (8),
.BR pvcreate (8),
.BR pvdisplay (8),
.BR pvmove (8),
.BR pvremove (8),
.BR pvs (8),
.BR pvscan (8),
.BR vgcfgbackup (8),
.BR vgchange  (8),
.BR vgck (8),
.BR vgconvert (8),
.BR vgcreate (8),
.BR vgdisplay (8),
.BR vgextend (8),
.BR vgimport (8),
.BR vgimportclone (8),
.BR vgmerge (8),
.BR vgmknodes (8),
.BR vgreduce (8),
.BR vgremove (8),
.BR vgrename (8),
.BR vgs (8),
.BR vgscan (8),
.BR vgsplit (8),
.BR readline (3)