---
name: "funionfs"
section: "1"
platform: "linux"
package: "funionfs"
version: "0.4.3-6"
release: "Debian 5.0 (Lenny)"
platforms: ["linux"]
url: "https://new.carta.tech/funionfs"
---

# funionfs(1)

user-space directory concatenation.

## NAME

funionfs - user-space directory concatenation.

## SYNOPSIS

**funionfs**  *upper\_dir mountpoint \[ option \] ...*

## OPTIONS

    \-o opt,\[opt...\]        mount options\
     \-h   --help            print help\
     \-V   --version         print version

Mount options include:\
    funionfs\_debug      print some debugging information\
    dirs=LIST           a colon separated list of directories\
       /branch1=rw      a directory in read-write mode\
       /branch1         if no permission is specified, the branch\
                        is in read-write mode\
       /branch2=ro      a directory in read-only mode\
    copyupuid=N         uid of the copied-up files (no default)\
    copyupgid=N         gid of the copied-up files (no default)\
    copyupmode=N        mode of the copied-up files (no default)\
    del\_string=N        string to mark a deleted file (default: \_DELETED~ )\
    delete=TYPE         specifies how funionfs deletes and renames\
       all (default)    delete all objects in read-write branch (default)\
                        and add a whiteout file if objects exists in\
                        read-only branches.\
       whiteout         only add a whiteout file in upper (rw) branch\
                        or delete file in upper branch.\
    copyup=TYPE         specifies how to manage attributes\
       preserve         preserve uid, gid and mode of object (default)\
       currentuser      the object is owned by the user doing the operation\
       mounter          the object is owned by the mounter

There is no implementation of -o delete and -o copyup for now.

You could use the mount command instead :\
    mount -t fuse funionfs#/upper\_dir mountpoint \[ options \]

If you want to name all directories in '-o dirs=', then pass "none" as upper\_dir

## DESCRIPTION

*funionfs* concatenates directories mentioned in options (and *upper\_dir* ) to *mountpoint.* Also, although some (but not all) of the directories are  read-only, you still can write in resulting mounted directory. For example, if you have files  *a/a* and  *b/b* and mount mountpoint  *r* with "-o dirs=a=ro:b=ro:w=rw", then you will see files  *r/a* and *r/b.* You will be able to write to them, and original files will remain intact  (changes will go to *w* ). Note that it is impossible to have file with name ending by  *del\_string* value, if you create  *r/a\_DELETED~* in mentioned example, it will dissapear together with a.

## SEE ALSO

The source..

## BUGS

You cannot mount an overlay on / (the program that list the content of / will hang). This is probably due to a loop call of the fuse driver. There is no known solution for now.

Probably minor (or major) mistakes in not-so-frequent cases.

Not enough tested.