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https://github.com/toby63/shiftfs-dkms

shiftfs kernel module via dkms
https://github.com/toby63/shiftfs-dkms

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shiftfs kernel module via dkms

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README 

        

# shiftfs-dkms



## Content



* [About](#about)

* [Limitations and Known Issues](#known-issues)

* [Status](#status)

* [Usecases](#usecases)

* [How to report bugs](#report-bugs)

* [Credits](#credits)

* [Copyright](#copyrightlicense)



---



## About



This repo provides scripts to install the (Linux) kernel module **shiftfs** via dkms.   



### Status



This Repository: | Upstream development: |

--- | --- |

Mostly inactive at the moment | active |



### About shiftfs



shiftfs is a kernel filesystem for the Linux kernel.   

It provides easier uid/gid-shifting for containers and can be used for example with [Incus](https://linuxcontainers.org/incus/introduction/) and LXD (see also: [Usecases](#usecases)).



shiftfs was made by:   

See [Credits](#credits)



Further information on shiftfs can be found in the Ubuntu kernel repos (see **Overview of Branches/Versions** below for specific links) and in the official Linuxcontainers.org Forum (the following link might be outdated, it was the original announcement):

https://discuss.linuxcontainers.org/t/trying-out-shiftfs/5155



### Important Info



The official successor of shiftfs is available now.



The new approach called "**idmapped mounts**" is natively included in recent Linux kernels (since kernel version **5.12**) - so there is no need for dkms-modules anymore. 



Support for the new approach is implemented in Incus and LXD (since version **4.16**) and the transition is seamless, so Incus and LXD will automatically switch to the new approach, if available, and all commands/options stay the same.   

**Update:** The following filesystems are now supported as underlying filesystems for containers and volumes: ext4, xfs, vfat, btrfs (since kernel version **5.15**), ZFS (recent kernels) and cephfs (recent kernels).



So the only reason to still use shiftfs is if you use older kernels, or have other specific reasons.



### Shiftfs (Alternative)



If you still need to use shiftfs, then the original shiftfs (the version used in this repo) is still available for:



- Newer kernel versions (the end of support is unknown for now, upstream will probably announce it someday (see also: [Issue 24](https://github.com/toby63/shiftfs-dkms/issues/24))), including: **6.1** and newer

- Longterm kernel versions: **5.15**, **5.10** and **5.4**



See **Overview of Branches/Versions** below for more information on each available version in this repo.   



Sources:



- Official LXD forum:

    - [Comment 1](https://discuss.linuxcontainers.org/t/shared-folder-between-container-and-host-is-cached/10725/2)

    - [Comment 2](https://discuss.linuxcontainers.org/t/lxd-4-16-has-been-released/11547/13)

    - [Comment 3](https://discuss.linuxcontainers.org/t/shared-folder-between-container-and-host-is-cached/10725/12)

    - [Comment 4](https://discuss.linuxcontainers.org/t/lxd-4-16-has-been-released/11547/16)

    - [Comment 5](https://discuss.linuxcontainers.org/t/lxd-4-16-has-been-released/11547/18)

- [LXD Pull Request](https://github.com/lxc/lxd/pull/8778)



### Overview of Branches/Versions



There are different versions of shiftfs.c for different kernel versions, so I cover a few of them:



| Branch/Version: | For Kernel(version): | Further Notes: |

| --- | --- | --- |

| - | 6.3.x | I did not set up a branch yet, but you can try to replace the shiftfs.c file from k6.1 with [this one](https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/mantic/tree/fs/shiftfs.c?h=master-next&id=94b75e19475892372aca91a67f71f51121e6f714). You also need to adjust **dkms.conf**. |

| [k6.1](https://github.com/toby63/shiftfs-dkms/tree/k6.1) | 6.1.x and 6.2.x | Does not work with 6.0.x. Also take a look at the [Notes](https://github.com/toby63/shiftfs-dkms/blob/k6.1/README.md#about)! |

| [k5.18](https://github.com/toby63/shiftfs-dkms/tree/k5.18) | 5.18.x, 5.19.x (and probably 6.0.x) | 5.19.x and 6.0.x are not tested. Kernel versions are deprecated upstream, see [kernel.org](https://www.kernel.org/). |

| [k5.17](https://github.com/toby63/shiftfs-dkms/tree/k5.17) | 5.17.x | Kernel version is deprecated upstream, see [kernel.org](https://www.kernel.org/). |

| [k5.16](https://github.com/toby63/shiftfs-dkms/tree/k5.16) | 5.15.x (longterm version) (and probably 5.16.x) | - |

| [k5.13](https://github.com/toby63/shiftfs-dkms/tree/k5.13) | 5.13.x (and probably 5.14.x) | Kernel versions are deprecated upstream, see [kernel.org](https://www.kernel.org/). |

| [k5.10](https://github.com/toby63/shiftfs-dkms/tree/k5.10) | 5.10.x (longterm version) and 5.8.x | - |

| [k5.4](https://github.com/toby63/shiftfs-dkms/tree/k5.4) | 5.4 (longterm version) | - |



#### What about other kernel versions?



Other kernel versions that are newer than 5.x might work, but there is no guarantee and I will not provide that.

You have the best chances if you search inside the Ubuntu kernel repos and might find a version that matches your kernel version (e.g. [hirsute kernel repo - master next](https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/hirsute/tree/fs/shiftfs.c?h=master-next) for 5.11).



shiftfs will most likely not work on kernels older than version 5.x.

Thus the only recent and active branch newer than 5 is 5.4.

See also [kernel.org](https://www.kernel.org/).



## Known Issues



* **Regarding Overlayfs inside a container:**

shiftfs can prevent the use of overlayfs **inside a container**.      

A usecase for this is running Docker with the overlayfs-storage driver **inside a lxd container**.   

A Kernelpatch that solves this is available, but it's not included in the mainline kernel (yet).

To my knowledge only Ubuntu included it (see [solved bug report](https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1846272)).



  For **workarounds and more information** see:

[Issue 2 of this repo](https://github.com/toby63/shiftfs-dkms/issues/2#issuecomment-614688392)



* More Issues may be found in the [Ubuntu Kernel Bug Tracker](https://bugs.launchpad.net/ubuntu/+source/linux?field.searchtext=shiftfs&search=Search&field.status%3Alist=NEW&field.status%3Alist=INCOMPLETE_WITH_RESPONSE&field.status%3Alist=INCOMPLETE_WITHOUT_RESPONSE&field.status%3Alist=CONFIRMED&field.status%3Alist=TRIAGED&field.status%3Alist=INPROGRESS&field.status%3Alist=FIXCOMMITTED&field.assignee=&field.bug_reporter=&field.omit_dupes=on&field.has_patch=&field.has_no_package=).



If you want to post a testreport, take a look at: [Testreports Issue on Github](https://github.com/toby63/shiftfs-dkms/issues/3).



## Usecases



* **Incus**: See my [GitHub wiki](https://github.com/toby63/shiftfs-dkms/wiki/Use-shift(fs)-in-Incus) and the [Linuxcontainers Forum - Share Folders and Volumes](https://discuss.linuxcontainers.org/t/share-folders-and-volumes-between-host-and-containers/7735)



* **LXD** (might be outdated): How to use shiftfs with LXD is described in [my wiki](https://github.com/toby63/shiftfs-dkms/wiki/Use-shiftfs-in-LXD)     

  and in the official Forum of LXD: [Usecases for shiftfs](https://discuss.linuxcontainers.org/t/lxd-usecases-of-shiftfs-volume-disk-share/7735) and [Trying out shiftfs](https://discuss.linuxcontainers.org/t/trying-out-shiftfs/5155).



## Report bugs



 Report bugs first at:

 https://github.com/toby63/shiftfs-dkms/issues



## Credits



* shiftfs was made by:

   * James Bottomley

   * Seth Forshee 

   * Christian Brauner    

   

   (recent info is in the shiftfs.c file (See: footer -> tag: MODULE_AUTHOR))



* Some files are based on the Debian package repo of bbswitch (https://salsa.debian.org/nvidia-team/bbswitch), including:

   * dkms.conf

   * Makefile

   * Makefile.dkms

   

* Special thanks to:

   * Stéphane Graber @stgraber

   * Christian Brauner @brauner   

   

  for the helpful advice.



## Copyright/License



General Public License, Version 2



See: [LICENSE](LICENSE)