rclone serve sftp
Serve the remote over SFTP.
Synopsis
Run an SFTP server to serve a remote over SFTP. This can be used with an SFTP client or you can make a remote of type sftp to use with it.
You can use the filter flags (e.g. --include, --exclude)
to control what is served.
The server will respond to a small number of shell commands, mainly md5sum, sha1sum and df, which enable it to provide support for checksums and the about feature when accessed from an sftp remote.
Note that this server uses standard 32 KiB packet payload size, which means you must not configure the client to expect anything else, e.g. with the chunk_size option on an sftp remote.
The server will log errors. Use -v to see access logs.
--bwlimit will be respected for file transfers.
Use --stats to control the stats printing.
You must provide some means of authentication, either with
--user/--pass, an authorized keys file (specify location with
--authorized-keys - the default is the same as ssh), an
--auth-proxy, or set the --no-auth flag for no
authentication when logging in.
If you don't supply a host --key then rclone will generate rsa, ecdsa
and ed25519 variants, and cache them for later use in rclone's cache
directory (see rclone help flags cache-dir) in the "serve-sftp"
directory.
By default the server binds to localhost:2022 - if you want it to be
reachable externally then supply --addr :2022 for example.
This also supports being run with socket activation, in which case it will listen on the first passed FD. It can be configured with .socket and .service unit files as described in https://www.freedesktop.org/software/systemd/man/latest/systemd.socket.html
Socket activation can be tested ad-hoc with the systemd-socket-activatecommand:
systemd-socket-activate -l 2222 -- rclone serve sftp :local:vfs/
This will socket-activate rclone on the first connection to port 2222 over TCP.
Note that the default of --vfs-cache-mode off is fine for the rclone
sftp backend, but it may not be with other SFTP clients.
If --stdio is specified, rclone will serve SFTP over stdio, which can
be used with sshd via ~/.ssh/authorized_keys, for example:
restrict,command="rclone serve sftp --stdio ./photos" ssh-rsa ...
On the client you need to set --transfers 1 when using --stdio.
Otherwise multiple instances of the rclone server are started by OpenSSH
which can lead to "corrupted on transfer" errors. This is the case because
the client chooses indiscriminately which server to send commands to while
the servers all have different views of the state of the filing system.
The "restrict" in authorized_keys prevents SHA1SUMs and MD5SUMs from being
used. Omitting "restrict" and using --sftp-path-override to enable
checksumming is possible but less secure and you could use the SFTP server
provided by OpenSSH in this case.
VFS - Virtual File System
This command uses the VFS layer. This adapts the cloud storage objects that rclone uses into something which looks much more like a disk filing system.
Cloud storage objects have lots of properties which aren't like disk files - you can't extend them or write to the middle of them, so the VFS layer has to deal with that. Because there is no one right way of doing this there are various options explained below.
The VFS layer also implements a directory cache - this caches info about files and directories (but not the data) in memory.
VFS Directory Cache
Using the --dir-cache-time flag, you can control how long a
directory should be considered up to date and not refreshed from the
backend. Changes made through the VFS will appear immediately or
invalidate the cache.
--dir-cache-time duration Time to cache directory entries for (default 5m0s)
--poll-interval duration Time to wait between polling for changes. Must be smaller than dir-cache-time. Only on supported remotes. Set to 0 to disable (default 1m0s)
However, changes made directly on the cloud storage by the web interface or a different copy of rclone will only be picked up once the directory cache expires if the backend configured does not support polling for changes. If the backend supports polling, changes will be picked up within the polling interval.
You can send a SIGHUP signal to rclone for it to flush all
directory caches, regardless of how old they are. Assuming only one
rclone instance is running, you can reset the cache like this:
kill -SIGHUP $(pidof rclone)
If you configure rclone with a remote control then you can use rclone rc to flush the whole directory cache:
rclone rc vfs/forget
Or individual files or directories:
rclone rc vfs/forget file=path/to/file dir=path/to/dir
VFS File Buffering
The --buffer-size flag determines the amount of memory,
that will be used to buffer data in advance.
Each open file will try to keep the specified amount of data in memory at all times. The buffered data is bound to one open file and won't be shared.
This flag is a upper limit for the used memory per open file. The buffer will only use memory for data that is downloaded but not not yet read. If the buffer is empty, only a small amount of memory will be used.
The maximum memory used by rclone for buffering can be up to
--buffer-size * open files.
VFS File Caching
These flags control the VFS file caching options. File caching is necessary to make the VFS layer appear compatible with a normal file system. It can be disabled at the cost of some compatibility.
For example you'll need to enable VFS caching if you want to read and write simultaneously to a file. See below for more details.
Note that the VFS cache is separate from the cache backend and you may find that you need one or the other or both.
--cache-dir string Directory rclone will use for caching.
--vfs-cache-mode CacheMode Cache mode off|minimal|writes|full (default off)
--vfs-cache-max-age duration Max time since last access of objects in the cache (default 1h0m0s)
--vfs-cache-max-size SizeSuffix Max total size of objects in the cache (default off)
--vfs-cache-min-free-space SizeSuffix Target minimum free space on the disk containing the cache (default off)
--vfs-cache-poll-interval duration Interval to poll the cache for stale objects (default 1m0s)
--vfs-write-back duration Time to writeback files after last use when using cache (default 5s)
If run with -vv rclone will print the location of the file cache. The
files are stored in the user cache file area which is OS dependent but
can be controlled with --cache-dir or setting the appropriate
environment variable.
The cache has 4 different modes selected by --vfs-cache-mode.
The higher the cache mode the more compatible rclone becomes at the
cost of using disk space.
Note that files are written back to the remote only when they are
closed and if they haven't been accessed for --vfs-write-back
seconds. If rclone is quit or dies with files that haven't been
uploaded, these will be uploaded next time rclone is run with the same
flags.
If using --vfs-cache-max-size or --vfs-cache-min-free-size note
that the cache may exceed these quotas for two reasons. Firstly
because it is only checked every --vfs-cache-poll-interval. Secondly
because open files cannot be evicted from the cache. When
--vfs-cache-max-size or --vfs-cache-min-free-size is exceeded,
rclone will attempt to evict the least accessed files from the cache
first. rclone will start with files that haven't been accessed for the
longest. This cache flushing strategy is efficient and more relevant
files are likely to remain cached.
The --vfs-cache-max-age will evict files from the cache
after the set time since last access has passed. The default value of
1 hour will start evicting files from cache that haven't been accessed
for 1 hour. When a cached file is accessed the 1 hour timer is reset to 0
and will wait for 1 more hour before evicting. Specify the time with
standard notation, s, m, h, d, w .
You should not run two copies of rclone using the same VFS cache
with the same or overlapping remotes if using --vfs-cache-mode > off.
This can potentially cause data corruption if you do. You can work
around this by giving each rclone its own cache hierarchy with
--cache-dir. You don't need to worry about this if the remotes in
use don't overlap.
--vfs-cache-mode off
In this mode (the default) the cache will read directly from the remote and write directly to the remote without caching anything on disk.
This will mean some operations are not possible
- Files can't be opened for both read AND write
- Files opened for write can't be seeked
- Existing files opened for write must have O_TRUNC set
- Files open for read with O_TRUNC will be opened write only
- Files open for write only will behave as if O_TRUNC was supplied
- Open modes O_APPEND, O_TRUNC are ignored
- If an upload fails it can't be retried
--vfs-cache-mode minimal
This is very similar to "off" except that files opened for read AND write will be buffered to disk. This means that files opened for write will be a lot more compatible, but uses the minimal disk space.
These operations are not possible
- Files opened for write only can't be seeked
- Existing files opened for write must have O_TRUNC set
- Files opened for write only will ignore O_APPEND, O_TRUNC
- If an upload fails it can't be retried
--vfs-cache-mode writes
In this mode files opened for read only are still read directly from the remote, write only and read/write files are buffered to disk first.
This mode should support all normal file system operations.
If an upload fails it will be retried at exponentially increasing intervals up to 1 minute.
--vfs-cache-mode full
In this mode all reads and writes are buffered to and from disk. When data is read from the remote this is buffered to disk as well.
In this mode the files in the cache will be sparse files and rclone will keep track of which bits of the files it has downloaded.
So if an application only reads the starts of each file, then rclone will only buffer the start of the file. These files will appear to be their full size in the cache, but they will be sparse files with only the data that has been downloaded present in them.
This mode should support all normal file system operations and is
otherwise identical to --vfs-cache-mode writes.
When reading a file rclone will read --buffer-size plus
--vfs-read-ahead bytes ahead. The --buffer-size is buffered in memory
whereas the --vfs-read-ahead is buffered on disk.
When using this mode it is recommended that --buffer-size is not set
too large and --vfs-read-ahead is set large if required.
IMPORTANT not all file systems support sparse files. In particular FAT/exFAT do not. Rclone will perform very badly if the cache directory is on a filesystem which doesn't support sparse files and it will log an ERROR message if one is detected.
Fingerprinting
Various parts of the VFS use fingerprinting to see if a local file copy has changed relative to a remote file. Fingerprints are made from:
- size
- modification time
- hash
where available on an object.
On some backends some of these attributes are slow to read (they take an extra API call per object, or extra work per object).
For example hash is slow with the local and sftp backends as
they have to read the entire file and hash it, and modtime is slow
with the s3, swift, ftp and qinqstor backends because they
need to do an extra API call to fetch it.
If you use the --vfs-fast-fingerprint flag then rclone will not
include the slow operations in the fingerprint. This makes the
fingerprinting less accurate but much faster and will improve the
opening time of cached files.
If you are running a vfs cache over local, s3 or swift backends
then using this flag is recommended.
Note that if you change the value of this flag, the fingerprints of the files in the cache may be invalidated and the files will need to be downloaded again.
VFS Chunked Reading
When rclone reads files from a remote it reads them in chunks. This means that rather than requesting the whole file rclone reads the chunk specified. This can reduce the used download quota for some remotes by requesting only chunks from the remote that are actually read, at the cost of an increased number of requests.
These flags control the chunking:
--vfs-read-chunk-size SizeSuffix Read the source objects in chunks (default 128M)
--vfs-read-chunk-size-limit SizeSuffix Max chunk doubling size (default off)
--vfs-read-chunk-streams int The number of parallel streams to read at once
The chunking behaves differently depending on the --vfs-read-chunk-streams parameter.
--vfs-read-chunk-streams == 0
Rclone will start reading a chunk of size --vfs-read-chunk-size,
and then double the size for each read. When --vfs-read-chunk-size-limit is
specified, and greater than --vfs-read-chunk-size, the chunk size for each
open file will get doubled only until the specified value is reached. If the
value is "off", which is the default, the limit is disabled and the chunk size
will grow indefinitely.
With --vfs-read-chunk-size 100M and --vfs-read-chunk-size-limit 0
the following parts will be downloaded: 0-100M, 100M-200M, 200M-300M, 300M-400M and so on.
When --vfs-read-chunk-size-limit 500M is specified, the result would be
0-100M, 100M-300M, 300M-700M, 700M-1200M, 1200M-1700M and so on.
Setting --vfs-read-chunk-size to 0 or "off" disables chunked reading.
The chunks will not be buffered in memory.
--vfs-read-chunk-streams > 0
Rclone reads --vfs-read-chunk-streams chunks of size
--vfs-read-chunk-size concurrently. The size for each read will stay
constant.
This improves performance performance massively on high latency links or very high bandwidth links to high performance object stores.
Some experimentation will be needed to find the optimum values of
--vfs-read-chunk-size and --vfs-read-chunk-streams as these will
depend on the backend in use and the latency to the backend.
For high performance object stores (eg AWS S3) a reasonable place to
start might be --vfs-read-chunk-streams 16 and
--vfs-read-chunk-size 4M. In testing with AWS S3 the performance
scaled roughly as the --vfs-read-chunk-streams setting.
Similar settings should work for high latency links, but depending on
the latency they may need more --vfs-read-chunk-streams in order to
get the throughput.
VFS Performance
These flags may be used to enable/disable features of the VFS for performance or other reasons. See also the chunked reading feature.
In particular S3 and Swift benefit hugely from the --no-modtime flag
(or use --use-server-modtime for a slightly different effect) as each
read of the modification time takes a transaction.
--no-checksum Don't compare checksums on up/download.
--no-modtime Don't read/write the modification time (can speed things up).
--no-seek Don't allow seeking in files.
--read-only Only allow read-only access.
Sometimes rclone is delivered reads or writes out of order. Rather than seeking rclone will wait a short time for the in sequence read or write to come in. These flags only come into effect when not using an on disk cache file.
--vfs-read-wait duration Time to wait for in-sequence read before seeking (default 20ms)
--vfs-write-wait duration Time to wait for in-sequence write before giving error (default 1s)
When using VFS write caching (--vfs-cache-mode with value writes or full),
the global flag --transfers can be set to adjust the number of parallel uploads of
modified files from the cache (the related global flag --checkers has no effect on the VFS).
--transfers int Number of file transfers to run in parallel (default 4)
VFS Case Sensitivity
Linux file systems are case-sensitive: two files can differ only by case, and the exact case must be used when opening a file.
File systems in modern Windows are case-insensitive but case-preserving: although existing files can be opened using any case, the exact case used to create the file is preserved and available for programs to query. It is not allowed for two files in the same directory to differ only by case.
Usually file systems on macOS are case-insensitive. It is possible to make macOS file systems case-sensitive but that is not the default.
The --vfs-case-insensitive VFS flag controls how rclone handles these
two cases. If its value is "false", rclone passes file names to the remote
as-is. If the flag is "true" (or appears without a value on the
command line), rclone may perform a "fixup" as explained below.
The user may specify a file name to open/delete/rename/etc with a case different than what is stored on the remote. If an argument refers to an existing file with exactly the same name, then the case of the existing file on the disk will be used. However, if a file name with exactly the same name is not found but a name differing only by case exists, rclone will transparently fixup the name. This fixup happens only when an existing file is requested. Case sensitivity of file names created anew by rclone is controlled by the underlying remote.
Note that case sensitivity of the operating system running rclone (the target) may differ from case sensitivity of a file system presented by rclone (the source). The flag controls whether "fixup" is performed to satisfy the target.
If the flag is not provided on the command line, then its default value depends on the operating system where rclone runs: "true" on Windows and macOS, "false" otherwise. If the flag is provided without a value, then it is "true".
The --no-unicode-normalization flag controls whether a similar "fixup" is
performed for filenames that differ but are canonically
equivalent with respect to
unicode. Unicode normalization can be particularly helpful for users of macOS,
which prefers form NFD instead of the NFC used by most other platforms. It is
therefore highly recommended to keep the default of false on macOS, to avoid
encoding compatibility issues.
In the (probably unlikely) event that a directory has multiple duplicate
filenames after applying case and unicode normalization, the --vfs-block-norm-dupes
flag allows hiding these duplicates. This comes with a performance tradeoff, as
rclone will have to scan the entire directory for duplicates when listing a
directory. For this reason, it is recommended to leave this disabled if not
needed. However, macOS users may wish to consider using it, as otherwise, if a
remote directory contains both NFC and NFD versions of the same filename, an odd
situation will occur: both versions of the file will be visible in the mount,
and both will appear to be editable, however, editing either version will
actually result in only the NFD version getting edited under the hood. --vfs-block- norm-dupes prevents this confusion by detecting this scenario, hiding the
duplicates, and logging an error, similar to how this is handled in rclone sync.
VFS Disk Options
This flag allows you to manually set the statistics about the filing system. It can be useful when those statistics cannot be read correctly automatically.
--vfs-disk-space-total-size Manually set the total disk space size (example: 256G, default: -1)
Alternate report of used bytes
Some backends, most notably S3, do not report the amount of bytes used.
If you need this information to be available when running df on the
filesystem, then pass the flag --vfs-used-is-size to rclone.
With this flag set, instead of relying on the backend to report this
information, rclone will scan the whole remote similar to rclone size
and compute the total used space itself.
WARNING. Contrary to rclone size, this flag ignores filters so that the
result is accurate. However, this is very inefficient and may cost lots of API
calls resulting in extra charges. Use it as a last resort and only with caching.
Auth Proxy
If you supply the parameter --auth-proxy /path/to/program then
rclone will use that program to generate backends on the fly which
then are used to authenticate incoming requests. This uses a simple
JSON based protocol with input on STDIN and output on STDOUT.
PLEASE NOTE: --auth-proxy and --authorized-keys cannot be used
together, if --auth-proxy is set the authorized keys option will be
ignored.
There is an example program bin/test_proxy.py in the rclone source code.
The program's job is to take a user and pass on the input and turn
those into the config for a backend on STDOUT in JSON format. This
config will have any default parameters for the backend added, but it
won't use configuration from environment variables or command line
options - it is the job of the proxy program to make a complete
config.
This config generated must have this extra parameter
_root- root to use for the backend
And it may have this parameter
_obscure- comma separated strings for parameters to obscure
If password authentication was used by the client, input to the proxy process (on STDIN) would look similar to this:
{
"user": "me",
"pass": "mypassword"
}
If public-key authentication was used by the client, input to the proxy process (on STDIN) would look similar to this:
{
"user": "me",
"public_key": "AAAAB3NzaC1yc2EAAAADAQABAAABAQDuwESFdAe14hVS6omeyX7edc...JQdf"
}
And as an example return this on STDOUT
{
"type": "sftp",
"_root": "",
"_obscure": "pass",
"user": "me",
"pass": "mypassword",
"host": "sftp.example.com"
}
This would mean that an SFTP backend would be created on the fly for
the user and pass/public_key returned in the output to the host given. Note
that since _obscure is set to pass, rclone will obscure the pass
parameter before creating the backend (which is required for sftp
backends).
The program can manipulate the supplied user in any way, for example
to make proxy to many different sftp backends, you could make the
user be user@example.com and then set the host to example.com
in the output and the user to user. For security you'd probably want
to restrict the host to a limited list.
Note that an internal cache is keyed on user so only use that for
configuration, don't use pass or public_key. This also means that if a user's
password or public-key is changed the cache will need to expire (which takes 5 mins)
before it takes effect.
This can be used to build general purpose proxies to any kind of backend that rclone supports.
rclone serve sftp remote:path [flags]
Options
--addr string IPaddress:Port or :Port to bind server to (default "localhost:2022")
--auth-proxy string A program to use to create the backend from the auth
--authorized-keys string Authorized keys file (default "~/.ssh/authorized_keys")
--dir-cache-time Duration Time to cache directory entries for (default 5m0s)
--dir-perms FileMode Directory permissions (default 777)
--file-perms FileMode File permissions (default 666)
--gid uint32 Override the gid field set by the filesystem (not supported on Windows) (default 1000)
-h, --help help for sftp
--key stringArray SSH private host key file (Can be multi-valued, leave blank to auto generate)
--no-auth Allow connections with no authentication if set
--no-checksum Don't compare checksums on up/download
--no-modtime Don't read/write the modification time (can speed things up)
--no-seek Don't allow seeking in files
--pass string Password for authentication
--poll-interval Duration Time to wait between polling for changes, must be smaller than dir-cache-time and only on supported remotes (set 0 to disable) (default 1m0s)
--read-only Only allow read-only access
--stdio Run an sftp server on stdin/stdout
--uid uint32 Override the uid field set by the filesystem (not supported on Windows) (default 1000)
--umask FileMode Override the permission bits set by the filesystem (not supported on Windows) (default 002)
--user string User name for authentication
--vfs-block-norm-dupes If duplicate filenames exist in the same directory (after normalization), log an error and hide the duplicates (may have a performance cost)
--vfs-cache-max-age Duration Max time since last access of objects in the cache (default 1h0m0s)
--vfs-cache-max-size SizeSuffix Max total size of objects in the cache (default off)
--vfs-cache-min-free-space SizeSuffix Target minimum free space on the disk containing the cache (default off)
--vfs-cache-mode CacheMode Cache mode off|minimal|writes|full (default off)
--vfs-cache-poll-interval Duration Interval to poll the cache for stale objects (default 1m0s)
--vfs-case-insensitive If a file name not found, find a case insensitive match
--vfs-disk-space-total-size SizeSuffix Specify the total space of disk (default off)
--vfs-fast-fingerprint Use fast (less accurate) fingerprints for change detection
--vfs-read-ahead SizeSuffix Extra read ahead over --buffer-size when using cache-mode full
--vfs-read-chunk-size SizeSuffix Read the source objects in chunks (default 128Mi)
--vfs-read-chunk-size-limit SizeSuffix If greater than --vfs-read-chunk-size, double the chunk size after each chunk read, until the limit is reached ('off' is unlimited) (default off)
--vfs-read-chunk-streams int The number of parallel streams to read at once
--vfs-read-wait Duration Time to wait for in-sequence read before seeking (default 20ms)
--vfs-refresh Refreshes the directory cache recursively in the background on start
--vfs-used-is-size rclone size Use the rclone size algorithm for Used size
--vfs-write-back Duration Time to writeback files after last use when using cache (default 5s)
--vfs-write-wait Duration Time to wait for in-sequence write before giving error (default 1s)
Options shared with other commands are described next. See the global flags page for global options not listed here.
Filter Options
Flags for filtering directory listings
--delete-excluded Delete files on dest excluded from sync
--exclude stringArray Exclude files matching pattern
--exclude-from stringArray Read file exclude patterns from file (use - to read from stdin)
--exclude-if-present stringArray Exclude directories if filename is present
--files-from stringArray Read list of source-file names from file (use - to read from stdin)
--files-from-raw stringArray Read list of source-file names from file without any processing of lines (use - to read from stdin)
-f, --filter stringArray Add a file filtering rule
--filter-from stringArray Read file filtering patterns from a file (use - to read from stdin)
--ignore-case Ignore case in filters (case insensitive)
--include stringArray Include files matching pattern
--include-from stringArray Read file include patterns from file (use - to read from stdin)
--max-age Duration Only transfer files younger than this in s or suffix ms|s|m|h|d|w|M|y (default off)
--max-depth int If set limits the recursion depth to this (default -1)
--max-size SizeSuffix Only transfer files smaller than this in KiB or suffix B|K|M|G|T|P (default off)
--metadata-exclude stringArray Exclude metadatas matching pattern
--metadata-exclude-from stringArray Read metadata exclude patterns from file (use - to read from stdin)
--metadata-filter stringArray Add a metadata filtering rule
--metadata-filter-from stringArray Read metadata filtering patterns from a file (use - to read from stdin)
--metadata-include stringArray Include metadatas matching pattern
--metadata-include-from stringArray Read metadata include patterns from file (use - to read from stdin)
--min-age Duration Only transfer files older than this in s or suffix ms|s|m|h|d|w|M|y (default off)
--min-size SizeSuffix Only transfer files bigger than this in KiB or suffix B|K|M|G|T|P (default off)
See Also
- rclone serve - Serve a remote over a protocol.
