Dmsetup command

A.2. DMSETUP command

dmsetup  A command is a command used with Device Mapper Command line wrapper for communication （wrapper）. You can use  dmsetup  Ordered  info、ls、status  and  deps  Options view LVM General information about the device , As described in the following sections .

of  dmsetup  Additional options and functions of the command , Please refer to  dmsetup(8) man page.

A.2.1. dmsetup info command

dmsetup info device  The order provides information about Device Mapper Equipment Overview . If no device name is specified , Then all currently configured Device Mapper Equipment information . If a device is specified , Then this command will only generate the device information .

dmsetup info  The command provides the following classification information ：

Name

Equipment name .LVM Devices are represented by volume group names and logical volume names separated by small horizontal lines . The small horizontal line in the source name will be converted to two small horizontal lines . In standard LVM In operation , This format should not be used LVM The device name is directly specified LVM equipment , It should use  vg/lv  Appoint .

name:raidVG-eph_d03ab0ae--09b6--43e5--a9e0--2dc4acf4dfd8

raidVG Express vg

eph_d03ab0ae--09b6--43e5--a9e0--2dc4acf4dfd8 Express lv

State

Possible device states are  SUSPENDED、ACTIVE  and  READ-ONLY.dmsetup suspend  The command sets the device status to  SUSPENDED. When a device is suspended , Will stop all... To the device I/O operation . Use  dmsetup resume  The command restores the device state to  ACTIVE.

Read Ahead

The number of read ahead data blocks of any open file being read by the system . By default , The kernel will automatically select an appropriate value . You can use  dmsetup  Ordered  --readahead  Option to change this value .

Tables present

The possible states of this type are  LIVE  and  INACTIVE.INACTIVE  Status indicates that the table has been loaded , And will be in  dmsetup resume  The command restores the state of a device to  ACTIVE  Switch when , At that time, the status of the form will be  LIVE. For details, please refer to  dmsetup man page.

Open count

The open reference count indicates the number of times the device was opened .mount  The command will open a device .

Event number

Number of events received so far . Use  dmsetup wait n  The command allows the user to wait for the n Events , Block the call before receiving the event .

Major, minor

Main equipment number and auxiliary equipment number

Number of targets

The number of segments that make up a device . for example ： A linear device that spans three disks has three targets . Linear devices start and end with a disk , Instead of intermediate linear devices, there are two goals .

UUID

Of the device UUID.

Here are  dmsetup info  Example of partial output of the command .

sudo dmsetup info raidVG-eph_d03ab0ae--09b6--43e5--a9e0--2dc4acf4dfd8
Name:              raidVG-eph_d03ab0ae--09b6--43e5--a9e0--2dc4acf4dfd8
State:             ACTIVE
Read Ahead:        256
Tables present:    LIVE
Open count:        1
Event number:      0
Major, minor:      253, 18
Number of targets: 1
UUID: LVM-4ovvx8eqezZ2or1OMqz0KUhyK8SZtTqdVLGvsPQd58pFUr8muAhxmaDYtEWN2NDG

A.2.2. dmsetup ls command

have access to  dmsetup ls  The command lists the device names of mapped devices . have access to  dmsetup ls --target target_type  The command lists devices that have at least one target of the specified type . of  dmsetup ls  Other options for , Please refer to  dmsetup ls man page.

The following example demonstrates the command to list the currently configured mapped device names .

sudo dmsetup ls 
raidVG-eph_3764d0aa--df56--478d--926c--e01dab91518a--linear	(253:8)
docker-253:0-12070-cbdbceb36eca043e9769c92d968e5fbb32d34743515f58d733bf1b1c16001171	(253:73)
raidVG-vm_data	(253:0)
raidVG-eph_0443b779--cb51--478a--9c4d--bc2a7c35c571--meta	(253:34)
docker-253:0-12070-7684cc6f46a62e77a48b0eefe1dfbc2aee4b86daffc3d9abf5272843385d51c2	(253:80)
docker-253:0-12070-pool	(253:70)
docker-253:0-12070-875c736f340ba4094c7e90aed5dedf212ee8a912f01b11be3268f41098209d6f	(253:120)
raidVG-eph_a6d5292a--bff4--49da--8a8c--7b2835c144c1	(253:2)
docker-253:0-12070-d04ca7fd6e5713e88dd444c20deac92f10dc231f3e451cc0eddcbfb9770824c5	(253:84)
raidVG-eph_3764d0aa--df56--478d--926c--e01dab91518a	(253:6)
docker-253:0-12070-e5c60544db49425174f99b8e9128f57254775d95f1990c9cb325f41b55c3dc9c	(253:104)
raidVG-eph_d19e6f31--4e59--4301--af75--d4d1aa576a2c	(253:129)
raidVG-eph_e4bc6c27--dfa5--402d--b7f3--54fe77e954ae--meta	(253:33)
docker-253:0-12070-61d574220dddbadc6752e16be782bc81a55ee4ca9171b60d39eacbb068742e92	(253:96)

The following example demonstrates the command used to list the currently configured image mapping device names .

In multipath or other device mapper Stacked in the unit LVM The configuration file may be too complex .dmsetup ls The order provides a --tree  Options , The dependencies between devices can be displayed in tree form , As shown below .

sudo  dmsetup ls --tree
docker-253:0-12070-cbdbceb36eca043e9769c92d968e5fbb32d34743515f58d733bf1b1c16001171 (253:73)
 └─docker-253:0-12070-pool (253:70)
    ├─ (7:0)
    └─ (7:1)
raidVG-vm_data (253:0)
 ├─raidVG-vm_data--meta (253:1)
 │  └─ (8:4)
 └─raidVG-vm_data--linear (253:62)
    └─ (8:4)
raidVG-eph_0443b779--cb51--478a--9c4d--bc2a7c35c571--meta (253:34)
 └─ (8:4)
docker-253:0-12070-7684cc6f46a62e77a48b0eefe1dfbc2aee4b86daffc3d9abf5272843385d51c2 (253:80)
 └─docker-253:0-12070-pool (253:70)
    ├─ (7:0)
    └─ (7:1)
docker-253:0-12070-875c736f340ba4094c7e90aed5dedf212ee8a912f01b11be3268f41098209d6f (253:120)
 └─docker-253:0-12070-pool (253:70)
    ├─ (7:0)
    └─ (7:1)
raidVG-eph_a6d5292a--bff4--49da--8a8c--7b2835c144c1 (253:2)
 └─ (8:4)
docker-253:0-12070-d04ca7fd6e5713e88dd444c20deac92f10dc231f3e451cc0eddcbfb9770824c5 (253:84)
 └─docker-253:0-12070-pool (253:70)
    ├─ (7:0)
    └─ (7:1)
raidVG-eph_3764d0aa--df56--478d--926c--e01dab91518a (253:6)
 ├─raidVG-eph_3764d0aa--df56--478d--926c--e01dab91518a--meta (253:7)
 │  └─ (8:4)
 └─raidVG-eph_3764d0aa--df56--478d--926c--e01dab91518a--linear (253:8)
    └─ (8:4)
docker-253:0-12070-e5c60544db49425174f99b8e9128f57254775d95f1990c9cb325f41b55c3dc9c (253:104)
 └─docker-253:0-12070-pool (253:70)
    ├─ (7:0)
    └─ (7:1)

A.2.3. dmsetup status command

dmsetup status device  The command provides status information for each target in the specified device . If no device name is specified , The output result is all currently configured device mapper device information . have access to  dmsetup status --targettarget_type  The command lists devices that have at least one target of the specified type .

The following example demonstrates the command used to list the target states in all currently configured mapping devices .

 sudo  dmsetup status 
raidVG-eph_3764d0aa--df56--478d--926c--e01dab91518a--linear: 0 20971520 linear 
docker-253:0-12070-cbdbceb36eca043e9769c92d968e5fbb32d34743515f58d733bf1b1c16001171: 0 20971520 thin 639488 20971519
raidVG-vm_data: 0 1551892480 ksc-linear 
raidVG-eph_0443b779--cb51--478a--9c4d--bc2a7c35c571--meta: 0 8192 linear 
docker-253:0-12070-7684cc6f46a62e77a48b0eefe1dfbc2aee4b86daffc3d9abf5272843385d51c2: 0 20971520 thin 753792 20971519
docker-253:0-12070-pool: 0 419430400 thin-pool 968 21495/524288 2001462/3276800 - rw discard_passdown queue_if_no_space - 
docker-253:0-12070-875c736f340ba4094c7e90aed5dedf212ee8a912f01b11be3268f41098209d6f: 0 20971520 thin 252800 20971519
raidVG-eph_a6d5292a--bff4--49da--8a8c--7b2835c144c1: 0 20971520 linear 
docker-253:0-12070-d04ca7fd6e5713e88dd444c20deac92f10dc231f3e451cc0eddcbfb9770824c5: 0 20971520 thin 2049024 20971519
raidVG-eph_3764d0aa--df56--478d--926c--e01dab91518a: 0 20971520 ksc-linear 

Create a linear equipment

dmsetup create dm-name dm-table

dm-name    Is the name of the device to be created . If successful, it will be in /dev/mapper/ Under the table of contents Generate a file with this name

dm-table    Is to save this map device Of mapping table.

ordinary dm-table One example is ：

starting sector   The number of sectors   Linear mapping   Target device Start sector on target device

0 1025 linear /dev/sdb2 0

1025 1025 linear /dev/sdc2 0

Some block Of sector size , It can be used blockdev --getsize /dev/sdb2 To get .

If it is a newly partitioned disk , Need to use partprobe Let's update

sudo fdisk -l 

Disk /dev/mapper/raidVG-eph_8efd7082--1128--465b--b42b--b59c659593b2: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/mapper/raidVG-eph_8efd7082--1128--465b--b42b--b59c659593b2--meta: 4 MB, 4194304 bytes, 8192 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/mapper/raidVG-eph_8efd7082--1128--465b--b42b--b59c659593b2--linear: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes