Provided by: gocryptfs_1.7.1-1ubuntu0.1_amd64 
NAME
gocryptfs - create or mount an encrypted filesystem
SYNOPSIS
Initialize encrypted filesystem
gocryptfs -init [OPTIONS] CIPHERDIR
Mount
gocryptfs [OPTIONS] CIPHERDIR MOUNTPOINT [-o COMMA-SEPARATED-OPTIONS]
Change password
gocryptfs -passwd [OPTIONS] CIPHERDIR
Check consistency
gocryptfs -fsck [OPTIONS] CIPHERDIR
DESCRIPTION
gocryptfs is an encrypted overlay filesystem written in Go. Encrypted files are stored in
CIPHERDIR, and a plain-text view can be presented by mounting the filesystem at
MOUNTPOINT.
gocryptfs was inspired by encfs(1) and strives to fix its security issues while providing
good performance.
OPTIONS
Available options are listed below.
-aessiv
Use the AES-SIV encryption mode. This is slower than GCM but is secure with deterministic
nonces as used in “-reverse” mode.
-allow_other
By default, the Linux kernel prevents any other user (even root) to access a mounted FUSE
filesystem. Settings this option allows access for other users, subject to file
permission checking. Only works if user_allow_other is set in /etc/fuse.conf. This
option is equivalent to “allow_other” plus “default_permissions” described in fuse(8).
-config string
Use specified config file instead of CIPHERDIR/gocryptfs.conf.
-cpuprofile string
Write cpu profile to specified file.
-ctlsock string
Create a control socket at the specified location. The socket can be used to decrypt and
encrypt paths inside the filesystem. When using this option, make sure that the directory
you place the socket in is not world-accessible. For example, /run/user/UID/my.socket
would be suitable.
-d, -debug
Enable debug output.
-dev, -nodev
Enable (-dev) or disable (-nodev) device files in a gocryptfs mount (default: -nodev). If
both are specified, -nodev takes precedence. You need root permissions to use -dev.
-devrandom
Use /dev/random for generating the master key instead of the default Go implementation.
This is especially useful on embedded systems with Go versions prior to 1.9, which fall
back to weak random data when the getrandom syscall is blocking. Using this option can
block indefinitely when the kernel cannot harvest enough entropy.
-e PATH, -exclude PATH
Only for reverse mode: exclude relative plaintext path from the encrypted view, matching
only from root of mounted filesystem. Can be passed multiple times. Example:
gocryptfs -reverse -exclude Music -exclude Movies /home/user /mnt/user.encrypted
See also -exclude-wildcard, -exclude-from and the EXCLUDING FILES section.
-ew PATH, -exclude-wildcard PATH
Only for reverse mode: exclude paths from the encrypted view, matching anywhere.
Wildcards supported. Can be passed multiple times. Example:
gocryptfs -reverse -exclude-wildcard '*~' /home/user /mnt/user.encrypted
See also -exclude, -exclude-from and the EXCLUDING FILES section.
-exclude-from FILE
Only for reverse mode: reads exclusion patters (using -exclude-wildcard syntax) from a
file. Can be passed multiple times. Example:
gocryptfs -reverse -exclude-from ~/crypt-exclusions /home/user /mnt/user.encrypted
See also -exclude, -exclude-wildcard and the EXCLUDING FILES section.
-exec, -noexec
Enable (-exec) or disable (-noexec) executables in a gocryptfs mount (default: -exec). If
both are specified, -noexec takes precedence.
-extpass string
Use an external program (like ssh-askpass) for the password prompt. The program should
return the password on stdout, a trailing newline is stripped by gocryptfs. If you just
want to read from a password file, see -passfile.
When -extpass is specified once, the string argument will be split on spaces. For
example, -extpass "md5sum my password.txt" will be executed as "md5sum" "my"
"password.txt", which is NOT what you want.
Specify -extpass twice or more to use the string arguments as-is. For example, you DO
want to call md5sum like this: -extpass "md5sum" -extpass "my password.txt".
If you want to prevent splitting on spaces but don’t want to pass arguments to your
program, use "--", which is accepted by most programs: -extpass "my program" -extpass "--"
-fg, -f
Stay in the foreground instead of forking away. Implies “-nosyslog”. For compatibility,
“-f” is also accepted, but “-fg” is preferred.
-force_owner string
If given a string of the form “uid:gid” (where both “uid” and “gid” are substituted with
positive integers), presents all files as owned by the given uid and gid, regardless of
their actual ownership. Implies “allow_other”.
This is rarely desired behavior: One should usually run gocryptfs as the account which
owns the backing-store files, which should usually be one and the same with the account
intended to access the decrypted content. An example of a case where this may be useful
is a situation where content is stored on a filesystem that doesn’t properly support UNIX
ownership and permissions.
-forcedecode
Force decode of encrypted files even if the integrity check fails, instead of failing with
an IO error. Warning messages are still printed to syslog if corrupted files are
encountered. It can be useful to recover files from disks with bad sectors or other
corrupted media. It shall not be used if the origin of corruption is unknown, specially
if you want to run executable files.
For corrupted media, note that you probably want to use dd_rescue(1) instead, which will
recover all but the corrupted 4kB block.
This option makes no sense in reverse mode. It requires gocryptfs to be compiled with
openssl support and implies -openssl true. Because of this, it is not compatible with
-aessiv, that uses built-in Go crypto.
Setting this option forces the filesystem to read-only and noexec.
-fsck
Check CIPHERDIR for consistency. If corruption is found, the exit code is 26.
-fsname string
Override the filesystem name (first column in df -T). Can also be passed as “-o fsname=”
and is equivalent to libfuse’s option of the same name. By default, CIPHERDIR is used.
-fusedebug
Enable fuse library debug output.
-h, -help
Print a short help text that shows the more-often used options.
-hh
Long help text, shows all available options.
-hkdf
Use HKDF to derive separate keys for content and name encryption from the master key.
-i duration, -idle duration
Only for forward mode: automatically unmount the filesystem if it has been idle for the
specified duration. Durations can be specified like “500s” or “2h45m”. 0 (the default)
means stay mounted indefinitely.
-info
Pretty-print the contents of the config file for human consumption, stripping out
sensitive data.
-init
Initialize encrypted directory.
-ko
Pass additional mount options to the kernel (comma-separated list). FUSE filesystems are
mounted with “nodev,nosuid” by default. If gocryptfs runs as root, you can enable device
files by passing the opposite mount option, “dev”, and if you want to enable
suid-binaries, pass “suid”. “ro” (equivalent to passing the “-ro” option) and “noexec”
may also be interesting. For a complete list see the section FILESYSTEM-INDEPENDENT MOUNT
OPTIONS in mount(8). On MacOS, “local”, “noapplexattr”, “noappledouble” may be
interesting.
Note that unlike “-o”, “-ko” is a regular option and must be passed BEFORE the
directories. Example:
gocryptfs -ko noexec /tmp/foo /tmp/bar
-longnames
Store names longer than 176 bytes in extra files (default true) This flag is useful when
recovering old gocryptfs filesystems using “-masterkey”. It is ignored (stays at the
default) otherwise.
-masterkey string
Use a explicit master key specified on the command line or, if the special value “stdin”
is used, read the masterkey from stdin. This option can be used to mount a gocryptfs
filesystem without a config file. Note that the command line, and with it the master key,
is visible to anybody on the machine who can execute “ps -auxwww”. Use “-masterkey=stdin”
to avoid that risk.
The masterkey option is meant as a recovery option for emergencies, such as if you have
forgotten the password or lost the config file.
Even if a config file exists, it will not be used. All non-standard settings have to be
passed on the command line: -aessiv when you mount a filesystem that was created using
reverse mode, or -plaintextnames for a filesystem that was created with that option.
Examples:
-masterkey=6f717d8b-6b5f8e8a-fd0aa206-778ec093-62c5669b-abd229cd-241e00cd-b4d6713d
-masterkey=stdin
-memprofile string
Write memory profile to the specified file. This is useful when debugging memory usage of
gocryptfs.
-nodev
See -dev, -nodev.
-noexec
See -exec, -noexec.
-nofail
Having the nofail option in /etc/fstab instructs systemd to continue booting normally even
if the mount fails (see man systemd.fstab).
The option is ignored by gocryptfs itself and has no effect outside /etc/fstab.
-nonempty
Allow mounting over non-empty directories. FUSE by default disallows this to prevent
accidental shadowing of files.
-noprealloc
Disable preallocation before writing. By default, gocryptfs preallocates the space the
next write will take using fallocate(2) in mode FALLOC_FL_KEEP_SIZE. The preallocation
makes sure it cannot run out of space in the middle of the write, which would cause the
last 4kB block to be corrupt and unreadable.
On ext4, preallocation is fast and does not cause a noticeable performance hit.
Unfortunately, on Btrfs, preallocation is very slow, especially on rotational HDDs. The
“-noprealloc” option gives users the choice to trade robustness against out-of-space
errors for a massive speedup.
For benchmarks and more details of the issue see
https://github.com/rfjakob/gocryptfs/issues/63 .
-nosyslog
Diagnostic messages are normally redirected to syslog once gocryptfs daemonizes. This
option disables the redirection and messages will continue be printed to stdout and
stderr.
-nosuid
See -suid, -nosuid.
-notifypid int
Send USR1 to the specified process after successful mount. This is used internally for
daemonization.
-o COMMA-SEPARATED-OPTIONS
For compatibility with mount(1), options are also accepted as “-o COMMA-SEPARATED-OPTIONS”
at the end of the command line. For example, “-o q,zerokey” is equivalent to passing “-q
-zerokey”.
Note that you can only use options that are understood by gocryptfs with “-o”. If you
want to pass special flags to the kernel, you should use “-ko” (kernel option). This is
different in libfuse-based filesystems, that automatically pass any “-o” options they do
not understand along to the kernel.
Example:
gocryptfs /tmp/foo /tmp/bar -o q,zerokey
-openssl bool/“auto”
Use OpenSSL instead of built-in Go crypto (default “auto”). Using built-in crypto is 4x
slower unless your CPU has AES instructions and you are using Go 1.6+. In mode “auto”,
gocrypts chooses the faster option.
-passfile string
Read password from the specified file. A warning will be printed if there is more than
one line, and only the first line will be used. A single trailing newline is allowed and
does not cause a warning.
Before gocryptfs v1.7, using -passfile was equivant to writing -extpass="/bin/cat --
FILE". gocryptfs v1.7 and later directly read the file without invoking cat.
-passwd
Change the password. Will ask for the old password, check if it is correct, and ask for a
new one.
This can be used together with -masterkey if you forgot the password but know the master
key. Note that without the old password, gocryptfs cannot tell if the master key is
correct and will overwrite the old one without mercy. It will, however, create a backup
copy of the old config file as gocryptfs.conf.bak. Delete it after you have verified that
you can access your files with the new password.
-plaintextnames
Do not encrypt file names and symlink targets.
-q, -quiet
Quiet - silence informational messages.
-raw64
Use unpadded base64 encoding for file names. This gets rid of the trailing “\=\=”. A
filesystem created with this option can only be mounted using gocryptfs v1.2 and higher.
-reverse
Reverse mode shows a read-only encrypted view of a plaintext directory. Implies
“-aessiv”.
-rw, -ro
Mount the filesystem read-write (-rw, default) or read-only (-ro). If both are specified,
-ro takes precedence.
-scryptn int
scrypt cost parameter expressed as scryptn=log2(N). Possible values are 10 to 28,
representing N=2^10 to N=2^28.
Setting this to a lower value speeds up mounting and reduces its memory needs, but makes
the password susceptible to brute-force attacks. The default is 16.
-serialize_reads
The kernel usually submits multiple concurrent reads to service userspace requests and
kernel readahead. gocryptfs serves them concurrently and in arbitrary order. On backing
storage that performs poorly for concurrent or out-of-order reads (like Amazon Cloud
Drive), this behavior can cause very slow read speeds.
The -serialize_reads option does two things: (1) reads will be submitted one-by-one (no
concurrency) and (2) gocryptfs tries to order the reads by file offset order.
The ordering requires gocryptfs to wait a certain time before submitting a read. The
serialization introduces extra locking. These factors will limit throughput to below
70MB/s.
For more details visit https://github.com/rfjakob/gocryptfs/issues/92 .
-sharedstorage
Enable work-arounds so gocryptfs works better when the backing storage directory is
concurrently accessed by multiple gocryptfs instances.
At the moment, it does two things:
1. Disable stat() caching so changes to the backing storage show up immediately.
2. Disable hard link tracking, as the inode numbers on the backing storage are not stable
when files are deleted and re-created behind our back. This would otherwise produce
strange “file does not exist” and other errors.
When “-sharedstorage” is active, performance is reduced and hard links cannot be created.
Even with this flag set, you may hit occasional problems. Running gocryptfs on shared
storage does not receive as much testing as the usual (exclusive) use-case. Please test
your workload in advance and report any problems you may hit.
More info: https://github.com/rfjakob/gocryptfs/issues/156
-speed
Run crypto speed test. Benchmark Go’s built-in GCM against OpenSSL (if available). The
library that will be selected on “-openssl=auto” (the default) is marked as such.
-suid, -nosuid
Enable (-suid) or disable (-nosuid) suid and sgid executables in a gocryptfs mount
(default: -nosuid). If both are specified, -nosuid takes precedence. You need root
permissions to use -suid.
-trace string
Write execution trace to file. View the trace using “go tool trace FILE”.
-trezor
With -init: Protect the masterkey using a SatoshiLabs Trezor instead of a password.
This feature is disabled by default and must be enabled at compile time using:
./build.bash -tags enable_trezor
You can determine if your gocryptfs binary has Trezor support enabled checking if the
gocryptfs -version output contains the string enable_trezor.
-version
Print version and exit. The output contains three fields separated by “;”. Example:
“gocryptfs v1.1.1-5-g75b776c; go-fuse 6b801d3; 2016-11-01 go1.7.3”. Field 1 is the
gocryptfs version, field 2 is the version of the go-fuse library, field 3 is the compile
date and the Go version that was used.
-wpanic
When encountering a warning, panic and exit immediately. This is useful in regression
testing.
-zerokey
Use all-zero dummy master key. This options is only intended for automated testing as it
does not provide any security.
--
Stop option parsing. Helpful when CIPHERDIR may start with a dash “-”.
EXCLUDING FILES
In reverse mode, it is possible to exclude files from the encrypted view, using the
-exclude, -exclude-wildcard and -exclude-from options.
-exclude matches complete paths, so -exclude file.txt only excludes a file named file.txt
in the root of the mounted filesystem; files named file.txt in subdirectories are still
visible. (This option is kept for compatibility with the behavior up to version 1.6.x)
-exclude-wildcard matches files anywhere, so -exclude-wildcard file.txt excludes files
named file.txt in any directory. If you want to match complete paths, you can prefix the
filename with a /: -exclude-wildcard /file.txt excludes only file.txt in the root of the
mounted filesystem.
If there are many exclusions, you can use -exclude-from to read exclusion patterns from a
file. The syntax is that of -exclude-wildcard, so use a leading / to match complete
paths.
The rules for exclusion are that of gitignore (https://git-
scm.com/docs/gitignore#_pattern_format). In short:
1. A blank line matches no files, so it can serve as a separator for readability.
2. A line starting with # serves as a comment. Put a backslash (\) in front of the first
hash for patterns that begin with a hash.
3. Trailing spaces are ignored unless they are quoted with backslash (\).
4. An optional prefix ! negates the pattern; any matching file excluded by a previous
pattern will become included again. It is not possible to re-include a file if a
parent directory of that file is excluded. Put a backslash (\) in front of the first !
for patterns that begin with a literal !, for example, \!important!.txt.
5. If the pattern ends with a slash, it is removed for the purpose of the following
description, but it would only find a match with a directory. In other words, foo/
will match a directory foo and paths underneath it, but will not match a regular file
or a symbolic link foo.
6. If the pattern does not contain a slash /, it is treated as a shell glob pattern and
checked for a match against the pathname relative to the root of the mounted
filesystem.
7. Otherwise, the pattern is treated as a shell glob suitable for consumption by
fnmatch(3) with the FNM_PATHNAME flag: wildcards in the pattern will not match a / in
the pathname. For example, Documentation/*.html matches Documentation/git.html but not
Documentation/ppc/ppc.html or tools/perf/Documentation/perf.html.
8. A leading slash matches the beginning of the pathname. For example, /*.c matches
cat-file.c but not mozilla-sha1/sha1.c.
9. Two consecutive asterisks (**) in patterns matched against full pathname may have
special meaning:
i. A leading ** followed by a slash means match in all directories. For example,
**/foo matches file or directory foo anywhere, the same as pattern foo.
**/foo/bar matches file or directory bar anywhere that is directly under
directory foo.
ii. A trailing /** matches everything inside. For example, abc/** matches all files
inside directory abc, with infinite depth.
iii. A slash followed by two consecutive asterisks then a slash matches zero or more
directories. For example, a/**/b matches a/b, a/x/b, a/x/y/b and so on.
iv. Other consecutive asterisks are considered invalid.
EXAMPLES
Create an encrypted filesystem in directory “g1” and mount it on “g2”:
mkdir g1 g2
gocryptfs -init g1
gocryptfs g1 g2
Mount an ecrypted view of joe’s home directory using reverse mode:
mkdir /home/joe.crypt
gocryptfs -init -reverse /home/joe
gocryptfs -reverse /home/joe /home/joe.crypt
EXIT CODES
0: success
6: CIPHERDIR is not an empty directory (on “-init”)
10: MOUNTPOINT is not an empty directory
12: password incorrect
22: password is empty (on “-init”)
23: could not read gocryptfs.conf
24: could not write gocryptfs.conf (on “-init” or “-password”)
26: fsck found errors
other: please check the error message
SEE ALSO
mount(2) fuse(8) fallocate(2) encfs(1)
AUTHORS
github.com/rfjakob.
Aug 2017 GOCRYPTFS(1)