mergerfs/mkdocs/docs/pages/documentation/options.md

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# OPTIONS
These options are the same regardless of whether you use them with the
`mergerfs` commandline program, in fstab, or in a config file.
### mount options
- **config**: Path to a config file. Same arguments as below in
key=val / ini style format.
- **branches**: Colon delimited list of branches.
- **minfreespace=SIZE**: The minimum space value used for creation
policies. Can be overridden by branch specific option. Understands
'K', 'M', and 'G' to represent kilobyte, megabyte, and gigabyte
respectively. (default: 4G)
- **moveonenospc=BOOL|POLICY**: When enabled if a **write** fails with
**ENOSPC** (no space left on device) or **EDQUOT** (disk quota
exceeded) the policy selected will run to find a new location for
the file. An attempt to move the file to that branch will occur
(keeping all metadata possible) and if successful the original is
unlinked and the write retried. (default: false, true = mfs)
- **inodecalc=passthrough|path-hash|devino-hash|hybrid-hash**: Selects
the inode calculation algorithm. (default: hybrid-hash)
- **dropcacheonclose=BOOL**: When a file is requested to be closed
call `posix_fadvise` on it first to instruct the kernel that we no
longer need the data and it can drop its cache. Recommended when
**cache.files=partial|full|auto-full|per-process** to limit double
caching. (default: false)
- **direct-io-allow-mmap=BOOL**: On newer kernels (>= 6.6) it is
possible to disable file page caching while still allowing for
shared mmap support. mergerfs will enable this feature if available
but an option is provided to turn it off for testing and debugging
purposes. (default: true)
- **symlinkify=BOOL**: When enabled and a file is not writable and its
mtime or ctime is older than **symlinkify_timeout** files will be
reported as symlinks to the original files. Please read more below
before using. (default: false)
- **symlinkify_timeout=UINT**: Time to wait, in seconds, to activate
the **symlinkify** behavior. (default: 3600)
- **nullrw=BOOL**: Turns reads and writes into no-ops. The request
will succeed but do nothing. Useful for benchmarking
mergerfs. (default: false)
- **lazy-umount-mountpoint=BOOL**: mergerfs will attempt to "lazy
umount" the mountpoint before mounting itself. Useful when
performing live upgrades of mergerfs. (default: false)
- **ignorepponrename=BOOL**: Ignore path preserving on
rename. Typically rename and link act differently depending on the
policy of `create` (read below). Enabling this will cause rename and
link to always use the non-path preserving behavior. This means
files, when renamed or linked, will stay on the same
filesystem. (default: false)
- **export-support=BOOL**: Sets a low-level FUSE feature intended to
indicate the filesystem can support being exported via
NFS. (default: true)
- **security_capability=BOOL**: If false return ENOATTR when xattr
security.capability is queried. (default: true)
- **xattr=passthrough|noattr|nosys**: Runtime control of
xattrs. Default is to passthrough xattr requests. 'noattr' will
short circuit as if nothing exists. 'nosys' will respond with ENOSYS
as if xattrs are not supported or disabled. (default: passthrough)
- **link_cow=BOOL**: When enabled if a regular file is opened which
has a link count > 1 it will copy the file to a temporary file and
rename over the original. Breaking the link and providing a basic
copy-on-write function similar to cow-shell. (default: false)
- **statfs=base|full**: Controls how statfs works. 'base' means it
will always use all branches in statfs calculations. 'full' is in
effect path preserving and only includes branches where the path
exists. (default: base)
- **statfs_ignore=none|ro|nc**: 'ro' will cause statfs calculations to
ignore available space for branches mounted or tagged as 'read-only'
or 'no create'. 'nc' will ignore available space for branches tagged
as 'no create'. (default: none)
- **nfsopenhack=off|git|all**: A workaround for exporting mergerfs
over NFS where there are issues with creating files for write while
setting the mode to read-only. (default: off)
- **branches-mount-timeout=UINT**: Number of seconds to wait at
startup for branches to be a mount other than the mountpoint's
filesystem. (default: 0)
- **follow-symlinks=never|directory|regular|all**: Turns symlinks into
what they point to. (default: never)
- **link-exdev=passthrough|rel-symlink|abs-base-symlink|abs-pool-symlink**:
When a link fails with EXDEV optionally create a symlink to the file
instead.
- **rename-exdev=passthrough|rel-symlink|abs-symlink**: When a rename
fails with EXDEV optionally move the file to a special directory and
symlink to it.
- **readahead=UINT**: Set readahead (in kilobytes) for mergerfs and
branches if greater than 0. (default: 0)
- **posix_acl=BOOL**: Enable POSIX ACL support (if supported by kernel
and underlying filesystem). (default: false)
- **async_read=BOOL**: Perform reads asynchronously. If disabled or
unavailable the kernel will ensure there is at most one pending read
request per file handle and will attempt to order requests by
offset. (default: true)
- **fuse_msg_size=UINT**: Set the max number of pages per FUSE
message. Only available on Linux >= 4.20 and ignored
otherwise. (min: 1; max: 256; default: 256)
- **threads=INT**: Number of threads to use. When used alone
(`process-thread-count=-1`) it sets the number of threads reading
and processing FUSE messages. When used together it sets the number
of threads reading from FUSE. When set to zero it will attempt to
discover and use the number of logical cores. If the thread count is
set negative it will look up the number of cores then divide by the
absolute value. ie. threads=-2 on an 8 core machine will result in 8
/ 2 = 4 threads. There will always be at least 1 thread. If set to
-1 in combination with `process-thread-count` then it will try to
pick reasonable values based on CPU thread count. NOTE: higher
number of threads increases parallelism but usually decreases
throughput. (default: 0)
- **read-thread-count=INT**: Alias for `threads`.
- **process-thread-count=INT**: Enables separate thread pool to
asynchronously process FUSE requests. In this mode
`read-thread-count` refers to the number of threads reading FUSE
messages which are dispatched to process threads. -1 means disabled
otherwise acts like `read-thread-count`. (default: -1)
- **process-thread-queue-depth=UINT**: Sets the number of requests any
single process thread can have queued up at one time. Meaning the
total memory usage of the queues is queue depth multiplied by the
number of process threads plus read thread count. 0 sets the depth
to the same as the process thread count. (default: 0)
- **pin-threads=STR**: Selects a strategy to pin threads to CPUs
(default: unset)
- **flush-on-close=never|always|opened-for-write**: Flush data cache
on file close. Mostly for when writeback is enabled or merging
network filesystems. (default: opened-for-write)
- **scheduling-priority=INT**: Set mergerfs' scheduling
priority. Valid values range from -20 to 19. See `setpriority` man
page for more details. (default: -10)
- **fsname=STR**: Sets the name of the filesystem as seen in
**mount**, **df**, etc. Defaults to a list of the source paths
concatenated together with the longest common prefix removed.
- **func.FUNC=POLICY**: Sets the specific FUSE function's policy. See
below for the list of value types. Example: **func.getattr=newest**
- **func.readdir=seq|cosr|cor|cosr:INT|cor:INT**: Sets `readdir`
policy. INT value sets the number of threads to use for
concurrency. (default: seq)
- **category.action=POLICY**: Sets policy of all FUSE functions in the
action category. (default: epall)
- **category.create=POLICY**: Sets policy of all FUSE functions in the
create category. (default: epmfs)
- **category.search=POLICY**: Sets policy of all FUSE functions in the
search category. (default: ff)
- **cache.open=UINT**: 'open' policy cache timeout in
seconds. (default: 0)
- **cache.statfs=UINT**: 'statfs' cache timeout in seconds. (default: 0)
- **cache.attr=UINT**: File attribute cache timeout in
seconds. (default: 1)
- **cache.entry=UINT**: File name lookup cache timeout in
seconds. (default: 1)
- **cache.negative_entry=UINT**: Negative file name lookup cache
timeout in seconds. (default: 0)
- **cache.files=libfuse|off|partial|full|auto-full|per-process**: File
page caching mode (default: libfuse)
- **cache.files.process-names=LIST**: A pipe | delimited list of
process [comm](https://man7.org/linux/man-pages/man5/proc.5.html)
names to enable page caching for when
`cache.files=per-process`. (default: "rtorrent|qbittorrent-nox")
- **cache.writeback=BOOL**: Enable kernel writeback caching (default:
false)
- **cache.symlinks=BOOL**: Cache symlinks (if supported by kernel)
(default: false)
- **cache.readdir=BOOL**: Cache readdir (if supported by kernel)
(default: false)
- **parallel-direct-writes=BOOL**: Allow the kernel to dispatch
multiple, parallel (non-extending) write requests for files opened
with `cache.files=per-process` (if the process is not in `process-names`)
or `cache.files=off`. (This requires kernel support, and was added in v6.2)
- **direct_io**: deprecated - Bypass page cache. Use `cache.files=off`
instead. (default: false)
- **kernel_cache**: deprecated - Do not invalidate data cache on file
open. Use `cache.files=full` instead. (default: false)
- **auto_cache**: deprecated - Invalidate data cache if file mtime or
size change. Use `cache.files=auto-full` instead. (default: false)
- **async_read**: deprecated - Perform reads asynchronously. Use
`async_read=true` instead.
- **sync_read**: deprecated - Perform reads synchronously. Use
`async_read=false` instead.
- **splice_read**: deprecated - Does nothing.
- **splice_write**: deprecated - Does nothing.
- **splice_move**: deprecated - Does nothing.
- **allow_other**: deprecated - mergerfs v2.35.0 and newer sets this FUSE option
automatically if running as root.
- **use_ino**: deprecated - mergerfs should always control inode
calculation so this is enabled all the time.
**NOTE:** Options are evaluated in the order listed so if the options
are **func.rmdir=rand,category.action=ff** the **action** category
setting will override the **rmdir** setting.
**NOTE:** Always look at the documentation for the version of mergerfs
you're using. Not all features are available in older releases. Use
`man mergerfs` or find the docs as linked in the release.
#### Value Types
- BOOL = 'true' | 'false'
- INT = [MIN_INT,MAX_INT]
- UINT = [0,MAX_INT]
- SIZE = 'NNM'; NN = INT, M = 'K' | 'M' | 'G' | 'T'
- STR = string (may refer to an enumerated value, see details of
argument)
- FUNC = filesystem function
- CATEGORY = function category
- POLICY = mergerfs function policy
### branches
The 'branches' argument is a colon (':') delimited list of paths to be
pooled together. It does not matter if the paths are on the same or
different filesystems nor does it matter the filesystem type (within
reason). Used and available space will not be duplicated for paths on
the same filesystem and any features which aren't supported by the
underlying filesystem (such as file attributes or extended attributes)
will return the appropriate errors.
Branches currently have two options which can be set. A type which
impacts whether or not the branch is included in a policy calculation
and a individual minfreespace value. The values are set by prepending
an `=` at the end of a branch designation and using commas as
delimiters. Example: `/mnt/drive=RW,1234`
#### branch mode
- RW: (read/write) - Default behavior. Will be eligible in all policy
categories.
- RO: (read-only) - Will be excluded from `create` and `action`
policies. Same as a read-only mounted filesystem would be (though
faster to process).
- NC: (no-create) - Will be excluded from `create` policies. You can't
create on that branch but you can change or delete.
#### minfreespace
Same purpose and syntax as the global option but specific to the
branch. If not set the global value is used.
#### globbing
To make it easier to include multiple branches mergerfs supports
[globbing](http://linux.die.net/man/7/glob). **The globbing tokens
MUST be escaped when using via the shell else the shell itself will
apply the glob itself.**
```
```