A copy-on-write (COW) file system developed by Oracle included in the Linux kernel.

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How to create a read-only snapshot in btrfs?

As far as I understand, the snapshots made by btrfs subvolume snapshot are writable by default and are visible at a certain path under the mountpoint of your btrfs volume. How to setup the system so ...
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18 views

Arch Linux Server: How to spin down HDDs in a BTRFS Raid5 configuration?

This is my first question here; after extensive research I had to reach out for help. I’ve build a home server based on Arch Linux. It basically has two main purposes: running a Plex Media Server and ...
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1answer
1k views

How do you mount a specific btrfs subvolume?

Suppose I start with a non-btrfs system and then add a secondary drive that I format as btrfs. How would I mount /var/log on a subvolume of the new drive instead of on the original drive? Is this even ...
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3answers
50 views

How can I identify which directories are on a different file system?

Imagine I am in a directory (e.g., /mnt) where some of the directories are mountpoints of another file system, and other directories are legitimate directories on the same filesystem. Can I issue a ...
6
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2answers
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Resize a btrfs partition inside a logical LVM volume

Following derobert's trick to resize the underlying filesystem when resizing a LVM volume: lvm> lvextend -r -l +100%FREE /dev/VolGroup00/lvolhome fsck from util-linux 2.25.2 /sbin/fsck.btrfs: ...
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49 views

BTRFS send only new files without deleting anything on remote

I'm looking into replacing rsync with BTRFS tools, but I'm not sure if what I want to do is even possible. I have a small local volume and a large remote volume used for archiving. Files will be ...
2
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0answers
29 views

What do “snapper mount” and “snapper umount” do?

I'm using snapper with BTRFS under Ubuntu 16.04, and I'm confused about the "mount" and "umount" parameters. They are documented like this in the man page: mount number Mount a snapshot. ...
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30 views

IO Error when trying to create a Btrfs snapshot

In Fedora 23, my / partition is formatted as Btrfs: /dev/nvme0n1p4 / btrfs rw,seclabel,relatime,ssd,space_cache,subvolid=257,subvol=/root 0 0 Full output: $ sudo cat /proc/mounts sysfs /sys sysfs ...
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1answer
57 views

What are btrfs generation_errs?

I have a btrfs file system that I've scrubbed a few times and found some errors. If I check the device status I see that I have generation_errs: $ sudo btrfs device stats /dev/nvme0n1p5 [/dev/...
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35 views

Does changing your OS (fedora>OpenSuse) or FS (ext4>btrfs) “break” rsync?

I am using a rather simple script to do incremental backups of my laptop to my external HDD's, where the core line is probably the following: rsync -arbuv --delete --progress -exclude-from=/backup-...
2
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0answers
36 views

Btrfs adding smaller drive to RAID1

I have a RAID1 btrfs filesystem with 2 2Tb drives, and I had a spare 750 Gb hdd lying around, so I thought I would add it to the RAID so I could use some extra storage. Well, I added it to the volume,...
4
votes
2answers
573 views

ideal btrfs storage scheme to incorporate external USB HDD as backup media

Is there a way to leverage btrfs's advanced features (COW, snapshots, etc.) to continuously backup/mirror my main storage volume to an external USB HDD?
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3answers
6k views

What are the advantages of Btrfs for end users?

Btrfs has begun to gain some momentum in replacing ext4 as the default filesystem of choice for a few distributions such as Fedora Core 16. It is experimentally available in a number of other ...
4
votes
2answers
404 views

How to check (simulate), how much space will be freed after I remove a btrfs subvolume?

The question is not trivial. BTRFS is COW file system and one object stored on hard disk can be referenced by many files. I use BTRFS snapshots as a part of a backup solution on my production server....
6
votes
1answer
4k views

Clear unused space with zeros (btrfs)

How to clear unused space with zeros ? (I am asking for tool for btrfs filesystem) I'm looking for something smarter than cat /dev/zero > /mnt/X/big_zero ; sync; rm /mnt/X/big_zero Like ...
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0answers
45 views

Possible slab memory leak related to bio and btrfs?

I'm currently running a rebuild on a btrfs NAS (~20TB) that had a drive failure. It's going to take a few days. My problem is about once every 24 hours the RAM filled up and the kernel starts killing ...
0
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1answer
33 views

Verify file permissions

I did a fresh installation of OpenSUSE and copied all my files from the old home directory. The user and group names hadn't changed, and all the files seem to have proper permissions. However, I ran ...
0
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1answer
82 views

taking snapshots of a BTRFS volume mounted with nodatacow?

I plan to create two subvolumes on a BTRFS-formatted spinning disk. I plan to mount one of those subvolumes with nodatacow so that I can efficiently store virtual machine images and database files ...
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3answers
2k views

Modifying a BTRFS filesystem UUID

I've made backups of my BTRFS filesystem using Clonezilla, and have restored one of those backups to a file named 2013-11-29.sda3.img. I need to get some files out of this backup, but there's a hitch....
0
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1answer
64 views

Resumable transfer for btrfs send

I am planing to backup data via sending btrfs snapshots to an online storage. The storage is mounted as a LUKS encrypted container file on a cifs share. Later transfers will be reasonably fast, but ...
4
votes
2answers
29 views

Is there a way to determine compile-time state of a kernel flag from a running system?

I have a running kernel and I'm trying to determine whether it was compiled with support for BTRFS extended attributes. Is there a way to determine a running kernel's compile flags?
3
votes
1answer
78 views

Why does my tumbleweed opensuse fstab contain so many btrfs subvol entries?

What is the purpose/reasoning/technical-reason why my opensuse tumbleweed system has so many folders of my filesystem "wrapped" (not sure if that's the right word) as sub volumes on btrfs? Does it ...
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40 views

hidden directories to ls (not dot prefixed file)

I'm facing with a uncommon issue, which is: After btrfs read failure and a btrfs check --repair on my partition mounted in /home, it seems that some directories have disappeared. I explain : When I ...
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198 views

RAID: ZFS or Btrfs?

I've mounted my own NAS with ArchLinux on an old HDD. I want to add 3x4To to have real storage capabilites and I would like to use a RAID5 system with these 3 disks. I've read a lot about ZFS Raid-z ...
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2answers
1k views

Unknown btrfs error, partition won't mount

a day or so ago my btrfs partition just stopped working, which means i can't mount it anymore which is why my Fedora Linux doesn't boot anymore. I don't really have much information, but Gparted ...
6
votes
1answer
69 views

Make tar (or other) archive, with data block-aligned like in original files for better block-level deduplication?

How can one generate a tar file, so the contents of tarred files are block-aligned like in the original files, so one could benefit from block-level deduplication ( http://unix.stackexchange.com/a/...
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0answers
36 views

Mounting a (semi-?) rebalanced btrfs drive

Have a 2 drive raid1 btrfs array on Ubuntu 16.04 that I no longer need to be raid1. Thought I would try separating the the disks and converting one to a single drive to keep the data following these ...
2
votes
2answers
74 views

How to verify a file copy is reflink/CoW?

I'm playing with btrfs, which allows cp --reflink to copy-on-write. Other programs, such as lxc-clone, may use this feature as well. My question is, how to tell if a file is a CoW of another? Like for ...
3
votes
2answers
2k views

How to find data copies btrfs

I have deduplicated my btrfs filesystem with bedup, so now all duplicate files (above a certain size) are "reflink" copies. Is there any way to see, given a filename, what other files are the same ...
4
votes
2answers
155 views

How to find out if a file on btrfs is copy-on-write?

I know that cp has a --reflink option to control full copies vs. copy-on-write "copies". On btrfs, can I use ls (or some other command) to find out whether a file shares (in a copy-on-write senses) ...
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58 views

btrfs device add: different mount options than for seed?

I have a btrfs seed device, created with mixed data+metadata (mkfs.btrfs --mixed), and also --metadata single. This device is read-only. When doing btrfs device add /dev/sdc1 /mnt, is it possible to ...
6
votes
1answer
1k views

How to replace a device in BTRFS RAID-1 filesystem?

I have a BTRFS RAID-1 filesystem with 2 legs. One disk needs to be replaced because of re-occuring read errors. Thus, the plan is: add a 3rd leg -> result should be: 3 way mirror remove the faulty ...
0
votes
1answer
33 views

Max number of subdirectories in btrfs

Is there a maximum limit to the number of subdirectories in a single directory for btrfs like the 64,000 limit in ext4? (see here: http://stackoverflow.com/questions/22775011/what-is-the-maximum-...
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vote
2answers
131 views

fs synchronization among desktops

I have several workstations (laptops and desktops). I'd like to synchronize files among them such that each one is a mirror of the other. I used to run an NFS server and share files out, but that ...
3
votes
1answer
390 views

How to get error detection and correction on a single hard drive on linux (with btrfs or other methods)

One of the cool things about btrfs on linux is that it can correct bit rot if it has redundant data because of its per-block checksumming. I can get redundant data by setting up a raid1 with two disks....
2
votes
1answer
100 views

Btrfs+LXC: any way to show even rough estimated free space for quota'ed subvol hosting LXC container?

I'm experimenting with LXC using Btrfs as a backing store. Btrfs allows for easy snapshot/deduplication and is ideal for spinning up several "pseudo-VMs". The problem I'm having is that some of the ...
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34 views

why stat() can't get the real device number for ubifs

the man 2 stat struct stat { dev_t st_dev; /* ID of device containing file */ ino_t st_ino; /* inode number */ mode_t st_mode; /* protection */ nlink_t ...
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56 views

Btrfs - Using Flash Drive as Backup/Snapshot Location

I am working on a project where I have a small MiniITX PC running Debian Jessie (8.3) When I installed the OS initially: I chose the filesystem as btrfs. I am not using LVM or any extra partitions ...
0
votes
1answer
399 views

Filesystem is reporting a write error on a specific sector even after the partition is moved further

I am facing the following problem: btrfs reports write errors for sector 128 on device /dev/sdd: sd 6:0:0:0: [sdd] Invalid command failure sd 6:0:0:0: [sdd] Result: hostbyte=DID_OK driverbyte=...
1
vote
1answer
36 views

How to isolate snapshot volumes with btrfs?

If I create a snapshot of root with: btrfs subvolume snapshot -r / /snapshot-$(date +%s) I can then see this snapshot with ls / How do I make snapshots that are isolated from the volume that they ...
2
votes
0answers
38 views

Space efficiency of Btrfs reflinks vs hardlinks

A webpage referenced by the Wikipedia article on Btrfs claims that (emphasis mine) [Btrfs] reflinks have the same use as hardlinks, but are more space efficient. I thought that the opposite was ...
0
votes
1answer
508 views

Mount BTRFS on Android (usb OTG)

I am using btrFS as a filesystem for my external harddrive. I'd like to use it under Android. Is there any painless way to do so?
2
votes
1answer
86 views

Btrfs: available space not used after migrating from RAID1 to RAID6

I had 8 2TB disks running in a RAID1 setup but it started to get full so I converted it to a RAID6. However, it seems I can't use the space I've gained by switching to RAID6. My filesystem is pretty ...
3
votes
1answer
187 views

BTRFS, RAID5 and the minimum number of drives required

It's been my understanding that in order to have a RAID5 setup, one would need to incorporate a minimum of three drives. Basically (and probably poor paraphrasing) two blocks of data and a block of ...
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0answers
14 views

Cryptsetup boot many devices “timeout”

On my server, the crypttab file has 13 entries for every hard drive connected to it. 2 are for the system partitions, 2 are for the backup system and 9 are for the mediaserver and nfs stuff. Currently,...
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2answers
49 views

resolve bind mounts with a shell tool/script

currently i have a setup with two hardrives, one with xfs, the other one with btrfs on it. The root fs is mounted on the xfs, and the btrfs under /data. For verious reasons, the directory /var/www on ...
4
votes
1answer
67 views

cannot reduce the size of my Btrfs partition

I need to free up 4T on my LVM which is mainly taken by a Btrfs filesystem mounted on /data. I did: # btrfs fi resize -h btrfs filesystem resize: too few arguments usage: btrfs filesystem resize [...
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0answers
19 views

btrfs - how to list files stored in a block?

I have some troubles with my btrfs file system on Ubuntu (my partition automatically enter in read-only mode after the login screen). I would like to know if one can know which files are included in ...
0
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1answer
35 views

How to safely delete a regular directory that contains several btrfs snapshots inside it?

I have a regular directory than contains directly underneath it several btrfs snapshots. Is it safe to do an rm -rf on the parent directory, or do I need to first do a btrfs subvolume delete SUBVOL on ...
4
votes
1answer
252 views

How do I view the btrfs checksum of a file?

Btrfs calculates a crc32c checksum for each file. Is there a way I can view what checksum is stored (as opposed to just reading the file and recalculating it)?