plucky (1) fuse-overlayfs.1.gz

NAME

       fuse-overlayfs - overlayfs FUSE implementation

SYNOPSIS

       mounting
           fuse-overlayfs [-f] [--debug] [-o OPTS] MOUNT_TARGET

       unmounting
           fusermount -u mountpoint

DESCRIPTION

       fuse-overlayfs  provides  an  overlayfs  FUSE  implementation  so that it can be used since Linux 4.18 by
       unprivileged users in an user namespace.

OPTIONS

       --debug Enable debugging mode, can be very noisy.

       -o lowerdir=low1[:low2...]  A list of directories separated by :.  Their content is merged.

       -o upperdir=upperdir A directory merged on top of all the lowerdirs where all the  changes  done  to  the
       file system will be written.

       -o  workdir=workdir  A directory used internally by fuse-overlays, must be on the same file system as the
       upper dir.

       -o uidmapping=UID:MAPPED-UID:LEN[,UID2:MAPPED-UID2:LEN2]  -o  gidmapping=GID:MAPPED-GID:LEN[,GID2:MAPPED-
       GID2:LEN2] Specifies the dynamic UID/GID mapping used by fuse-overlayfs when reading/writing files to the
       system.

       The fuse-overlayfs dynamic mapping is an alternative and cheaper way to chown'ing the files on  the  host
       to accommodate the user namespace settings.

       It  is  useful  to  share the same storage among different user namespaces and counter effect the mapping
       done by the user namespace itself, and without requiring to chown the files.

       For example, given on the host two files like:

       $ stat -c %u:%g lower/a lower/b 0:0 1:1

       When we run in a user namespace with the following configuration: $ cat /proc/self/uid_map
                0       1000          1
                1     110000      65536

       We would see:

       $ stat -c %u:%g merged/a merged/b 65534:65534 65534:65534

       65534 is the overflow id used when the UID/GID is not known inside  the  user  namespace.   This  happens
       because both users 0:0 and 1:1 are not mapped.

       In     the    above    example,    if    we    mount    the    fuse-overlayfs    file    system    using:
       -ouidmapping=0:1000:1:1:110000:65536,gidmapping=0:1000:1:1:110000:65536,   which   is    the    namespace
       configuration specified on a single line, we'd see from the same user namespace:

       $ stat -c %u:%g merged/a merged/b 0:0 1:1

       Those are the same IDs visible from outside the user namespace.

       -o squash_to_root Every file and directory is owned by the root user (0:0).

       -o squash_to_uid=uid -o squash_to_gid=gid Every file and directory is owned by the specified uid or gid.

       It has higher precedence over squash_to_root.

       -o static_nlink Set st_nlink to the static value 1 for all directories.

       This  can  be useful for higher latency file systems such as NFS, where counting the number of hard links
       for a directory with many files can be a slow operation. With this option enabled,  the  number  of  hard
       links reported when running stat for any directory is 1.

       -o noacl Disable ACL support in the FUSE file system.

SEE ALSO

       fuse(8), mount(8), user_namespaces(7)

AVAILABILITY

       The  fuse-overlayfs  command  is  available  from  https://github.com/containers/fuse-overlayfs under GNU
       GENERAL PUBLIC LICENSE Version 3 or later.

                                                  User Commands                                fuse-overlayfs(1)