libgocryptfs/Documentation/MANPAGE.md

% GOCRYPTFS(1) % github.com/rfjakob % Oct 2016

NAME

gocryptfs - mount an encrypted directory

SYNOPSIS

Initialize encrypted filesystem

gocryptfs -init [OPTIONS] CIPHERDIR

Mount

gocryptfs [OPTIONS] CIPHERDIR MOUNTPOINT [-o COMMA-SEPARATED-OPTIONS]

Change password

gocryptfs -passwd [OPTIONS] CIPHERDIR

DESCRIPTION

Options:

-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 direcory you place the socket in is not world-accessible. For example, /run/user/UID/my.socket would be suitable.

-d, -debug

Enable debug output

-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. Using something like "cat /mypassword.txt" allows to mount the gocryptfs filesytem without user interaction.

-fg, -f

Stay in the foreground instead of forking away. Implies "-nosyslog". For compatability, "-f" is also accepted, but "-fg" is preferred.

-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

-init

Initialize encrypted directory

-ko

Pass additonal 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).

-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. 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". This is meant as a recovery option for emergencies, such as if you have forgotten your password.

Example master key:
6f717d8b-6b5f8e8a-fd0aa206-778ec093-62c5669b-abd229cd-241e00cd-b4d6713d

-memprofile string

Write memory profile to the specified file. This is useful when debugging memory usage of gocryptfs.

-nonempty

Allow mounting over non-empty directories. FUSE by default disallows this to prevent accidential 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.

-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".

-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. This is a shortcut for specifying '-extpass="/bin/cat -- FILE"'.

-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".

-ro

Mount the filesystem read-only

-scryptn int

scrypt cost parameter logN. Setting this to a lower value speeds up mounting but makes the password susceptible to brute-force attacks (default 16)

-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.

-version

Print version and exit. The output contains three fields seperated 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 "-".

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
12: password incorrect
other: please check the error message

SEE ALSO

fuse(8) fallocate(2)