Questions tagged [device-mapper]
The device mapper is a block layer component which allows the creation of virtual block devices. LVM2 is based on it.
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For the Device-Mapper framework, who is doing the development, and how do you contribute to it?
I've been using the device-mapper framework (dm-crypt, dm-verity), but there are some things I wish could be improved.
Where is the discussion about its development and is there a way to contribute to ...
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Do cryptsetup encryption from user space, possibly as ordinary user
I have the duty to create a package format which has its contents compressed and encrypted and which can be mounted.
I have modelled it to be a squashfs embedded in a cryptsetup raw device.
Alas, this ...
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LVM and device mapper: Logical Volume device sector size
This seems to be a problem regarding the sector size of the mapped device for a logical volume between different machines.
More specifically, I'd like to know if and how the sector size of a mapped ...
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LVM Device-mapper (dm-2) 100% busy
We have set up LVM stripping across 06 disk in our DB server for improving IOPS performance.
However during heavy load, it has been observed that device-mapper dm-2 asscociated with these 6 disks is ...
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How to guarantee temporary immutability of LVM2 LV at raw block level?
I inherited an Azure VM (Ubuntu 20.04) which has a 7 disk VG fully occupied by a RAID5 LV formatted as ext4.
I need to take backups and was hoping to use Azure Backup to snapshot the Azure Disks ...
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How to auto-mount external drive without using /etc/fstab
I have mounted an external drive using an entry/etc/fstab , UUID=ba6274de-e241-43ef-9dd0-5147c29e883a /mnt/500GB_Seagate_Drive xfs defaults,x-gvfs-show 0 0
I have other drives with do not have an ...
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How to find the mapping between the dm-? files and its corresponding LVM files from the running kernel
It seems that the mapping relationship between the dm-? files and its corresponding LVM files can only be statically gotten via the following configuration.
So is there any other way to directly find ...
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What is writing to my /dev/dm-2 Volume?
I'm running a STIG version of RHEL, and I’m having trouble figuring out how all of my logical volumes map.
/dev/mapper/vg1_audit seems to point to /dev/dm-2
/dev/vg1/lv_audit also seems to map to /dev/...
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Some "disappeared" dm-? files under the /dev directory
Recently I took over a few RHEL systems running with the native DM-multipath, which had been installed & configured by other persons.
My doubts focus on the following questions:
1). Why there ...
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List of applications using dsync or is dsync used in production?
We want to use dsync in production server, Is it production ready? I want to know the list applications using dsync. can someone provide me the list of applications which are using dsync.
Source code: ...
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How to disable device mapper for live.iso?
I made a live.iso by livemedia-creator. I use it to make livecd. However, when I boot it, the disk(/dev/sda) is always controlled by /dev/mapper. I want to make my iso boot without /dev/mapper enabled....
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Move a device mapper table from INACTIVE to LIVE without unsuspending
When a device mapper target is suspended, the table can be changed, causing the new table to move into the INACTIVE state. The INACTIVE table is changed to LIVE when the target resumes:
# dmsetup info ...
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How are /dev/dm-0 and /dev/mapper/control created, when using lvm?
AFAIK, lvm implementations are in userspace, and it basically sets up mapping tables using kernel's device mapper mechanism (dm-mod module), via the dmsetup command.
Is it correct that this is the ...
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Fakeraid partition missing (not mapped as a device on boot) after upgrade to Ubuntu 22.04
I have a RAID-0 volume with an NTFS partition that has worked fine for years on my dual-boot system (readable and writable by both Windows and Linux).
Today after doing a do-release-upgrade -d to ...
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Parted on /dev/mapper/, What are the differences between Ignore and Cancel?
I am using parted to partition a /dev/mapper/luks_device. I know that I have to use kpartx to load the partition mappings afterwards (with reference to this thread). However while creating partition ...
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How to check if a LUKS device is unlocked, without sudo permissions?
Is there any way to check if a LUKS device is unlocked, without having sudo permissions?
I'm aware of two questions, but all the answers require sudo.
It seems that I've found an indirect way (...
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Is it possible to re-attach a drive to an open DM-crypt device?
Imagine a setup where ZFS is on top of LUKS which sits on a physical drive.
While the FS is mounted, the drive drops out/is disconnected (user error, intermittent issue etc.).
Now we have the ...
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Properly Extend virtual volumes on a CentOS VM, new space in /dev/cl/ not occupied by /dev/mapper
I have a CentOS VM (on a windows host, managed with virtualbox) that ran out of disk space.
I extended the virtual disk size, then used gparted to assign the new space to the existing partition
Then I ...
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what is linux kernel module dm_bio_prison?
A kernel module name dm_bio_prison and descripted with "device-mapper bio prison" is loaded on a linux system. It is used by the modules dm_cache and dm_thin_pool.
#lsmod | grep ...
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The merits and demerits about the different FS mounting methods between non-DM and DM
Are there any other (de)merits about the following FS mounting methods？
For example:
the DM method, just means /dev/mapper/<VG>-<LV>, can handle its own multipath I/O.
the non-DM methods, ...
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Why does `mount /dev/dm-8` mount `/dev/dm-39` instead?
On a debian 10 GNU with Linux kernel system the following line does not - as expected - mount /dev/dm-8 but (imho incorreclty) /dev/dm-37:
mount /dev/dm-8 /mnt
I am puzzled really now the reason and/...
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How to setup mdadm raid1 auto-assembly, where external bitmap is itself on another mdadm raid1?
How can the assembling of a raid (as via information stored in mdadm.conf) succeed, given that its assembling requires a bitmap file, which itself is only available after another device has become ...
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Can linux device-mapper be used to throttle disk IO?
The device-mapper framework of the linux kernel offers many useful modes of operation or targets.
Some prominent are:
dm-crypt allowing to include encryption of block devices
dm-raid for multi device ...
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Suspend devmapper target when underlying device removed
If you create a table with dmsetup and the underlying device gets forced removed, the target will begin to throw I/O errors.
Is there any way to specify that the target should suspend itself if any of ...
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Where can I see the difference in those mounts?
# mount | grep 'rootvg-var\b'
/dev/mapper/rootvg-var on /var type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
/dev/mapper/rootvg-var on /var/lib/docker/containers type xfs (rw,relatime,seclabel,...
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Cryptsetup with dm-integrity - weird benchmark results
I'm benchmarking various cryptsetup volumes and I'm getting unexpected results on Debian.
I'm using numbers from this talk as a rough reference. One of the slides shows benchmark results for various ...
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What is mounted on what with xfs; storage drivers for docker
I have a virtual redhat linux machine, that I am using for Docker. Apparently, I haven't set it properly up for production mode as I am still running the storage mode as a loop-back device with ...
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dm-integrity standalone mapper device lost after reboot
I currently try to use dm-integrity to run in standalone mode. For that I install a plain ubuntu server 20.04 in a virtual box VM.
In the next steps I create the dm-integrity device, a ext4 ...
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How can I concatenate thousands of files into a single device
I'am using split to cut a an iso into multiples chunks. Then a can use cat to rebuild initial iso that I can convert into a mountable device with losetup and then mount.
The problem is when initial ...
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Can’t mount mapper device at boot on Debian
My /etc/fstab file is the following:
proc /proc proc defaults 0 0
/dev/root / ext4 rw,errors=remount-ro 0 1
tmpfs /dev/shm tmpfs mode=0777 ...
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Veritysetup Verification fails at hash-offset
I'm trying to get dm-verity to verify a sd-card partition. I did
veritysetup format --hash-offset=24215552 /dev/sdb4 /dev/sdb4
To create a hash device on the same device at the given offset.
Now I ...
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What is /dev/mapper/cachedev1?
I just got my first QNAP NAS, used to work mostly with Synology before, and I'm currently trying to figure out how the system uses LVM. Mostly out of curiosity.
In my specific case, it's a 2 bay NAS ...
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How the IOs are throttled from IO scheduler to scsi low level drivers
IO scheduler has a queue depth of 128 by default. And block device has a queue depth of 32 by default. Where does the IOs are buffered. Does IO scheduler send all IOs to scsi low level drivers and ...
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How can I xor two block devices together?
I'm looking for a way to create a virtual block device that when accessed returns the XOR of two block devices. I feel like dmsetup would be used here somewhere but I can't find anything related to ...
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Skipping the middle mapping with cryptsetup luksOpen
I'm mounting a bunch of encrypted disks like so
cryptsetup luksOpen some_source some_mapping &&
mount /dev/mapper/some_mapping /some_mountpoint
How can I abstract away the middle mapping?
I ...
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Have an SSD and HDD as the same filesystem and overflow from one to the other?
Is it possible in Linux (specifically OpenSUSE) to have an SSD and a HDD set up in such a way that they appear as a single filesystem, yet data is always written to the SSD until full, and then "...
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veritysetup verify successful but mount fails after upgrade to new kernel
We are using dm-verity for a squashfs root file system.
Using kernel 4.8.4 everything was ok, after upgrading to kernel 4.14.14 mount fails, even though the veritysetup verify command validates the ...
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Is there a way for a device mapper target to limit the rate at which i/o is sent to it?
I am writing a device mapper target and am having a issue. While running an i/o test, the number of i/o inflight to my target gets very high, presumably from the filesystem paging out the cache. At ...
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How to take space from one VG and add it to another?
I've seen that /dev/mapper/VGP4--CHK-LVP4--CHK is running out of space. I would like to increase this.
Filesystem Size Used Avail Use% Mounted on
udev ...
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dmsetup: Where is persistent metadata stored?
The dmsetup snapshot documentation says:
<persistent?> is P (Persistent) or N (Not persistent - will not survive
after reboot). O (Overflow) can be added as a persistent store option
to allow ...
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Can't create persistent snapshot device with `dmsetup`
I am trying to create a dmsetup snapshot device be able to rollback changes made by fsck.
I think I'm calling dmsetup incorrectly. Here's an example:
$ truncate -s 4096 real snapshot
$...
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Create a block device made of files
TL;DR:
Given 2TB worth of 4MB files, how would I create a block device with those files as backing storage?
Background
I want to trial use of Sia for storage, since:
Storing 1TB on Sia costs about $2 ...
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Is Block device aware of the actual user/process which initiates read/write?
The VFS knows which user/process has sent read/write request. Is the actual block device aware of these details.
Does 'bio' struct contain any details which point to the user space parameters? Using ...
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LVM volume on USB drive fails: Read-only file system
This is on a Raspberry Pi running Raspbian 8 (Linux kernel 4.9.) I have a 64 GB USB pen drive plugged (as /dev/sda) and configured as an LVM physical volume. There's only one volume group ("data") and ...
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After increasing chunksize in an LVM cache, files are no longer promoted to the cache
After running into issues with running out of kernel memory, I increased the chunksize of my lvmcache from the default (which I believe was 64k) to a much higher 8M.
After this change, blocks do not ...
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Devicemapper maintenance- dmsetup is missing
I manage docker environment on RHEL 7.1 host. Currently I use docker engine v1.9 and what I'd like to do is to upgrade this docker engine to v1.13.
My docker engine uses devicemappers as storage, and ...
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Why does libdevmapper have data structures?
As I'm looking through libdevmapper.h for clues on how to properly use device mapper ioctls (or potentially use libdevmapper instead), I'm confused as to why there is code in here for creating/...
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Documentation on Device Mapper ioctls?
In the Red Hat documentation on Device Mapper, it reads:
"the application interface to the Device Mapper is the ioctl system
call."
So far, I understand that the ioctls are sent to /dev/mapper/...
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How to make device mappings stay after reboot?
I notice that if a device mapping is created with the low-level dmsetup or through ioctls, the device mapping will no longer be there after reboot.
Is this normal? I am using a USB to test out ...
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Can dm-crypt be configured to ask for key on every read/write?
My understanding is that dm-crypt serves to abstract the actual block device so that the read/decrypt and write/encrypt happen automatically.
However, assuming a device mapping with target: crypt is ...
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