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117 lines
2.6 KiB
Groff
117 lines
2.6 KiB
Groff
.nh
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.TH fuse\-overlayfs 1 "User Commands"
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.SH NAME
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.PP
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fuse\-overlayfs \- overlayfs FUSE implementation
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.SH SYNOPSIS
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.PP
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mounting
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fuse\-overlayfs [\-f] [\-\-debug] [\-o OPTS] MOUNT\_TARGET
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.PP
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unmounting
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fusermount \-u mountpoint
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.SH DESCRIPTION
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.PP
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fuse\-overlayfs provides an overlayfs FUSE implementation so that it
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can be used since Linux 4.18 by unprivileged users in an user
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namespace.
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.SH OPTIONS
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.PP
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\fB\-\-debug\fP
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Enable debugging mode, can be very noisy.
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.PP
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\fB\-o lowerdir=low1[:low2...]\fP
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A list of directories separated by \fB\fC:\fR\&. Their content is merged.
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.PP
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\fB\-o upperdir=upperdir\fP
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A directory merged on top of all the lowerdirs where all the changes
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done to the file system will be written.
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.PP
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\fB\-o workdir=workdir\fP
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A directory used internally by fuse\-overlays, must be on the same file
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system as the upper dir.
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.PP
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\fB\-o workdir=workdir\fP
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A directory used internally by fuse\-overlays, must be on the same file
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system as the upper dir.
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.PP
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\fB\-o uidmapping=UID:MAPPED\-UID:LEN[,UID2:MAPPED\-UID2:LEN2]\fP
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\fB\-o gidmapping=GID:MAPPED\-GID:LEN[,GID2:MAPPED\-GID2:LEN2]\fP
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Specifies the dynamic UID/GID mapping used by fuse\-overlayfs when
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reading/writing files to the system.
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.PP
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The fuse\-overlayfs dynamic mapping is an alternative and cheaper way
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to chown'ing the files on the host to accomodate the user namespace
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settings.
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.PP
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It is useful to share the same storage among different user namespaces
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and counter effect the mapping done by the user namespace itself, and
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without requiring to chown the files.
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.PP
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For example, given on the host two files like:
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.PP
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$ stat \-c %u:%g lower/a lower/b
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0:0
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1:1
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.PP
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When we run in a user namespace with the following configuration:
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$ cat /proc/self/uid\_map
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0 1000 1
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1 110000 65536
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.PP
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We would see:
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.PP
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$ stat \-c %u:%g merged/a merged/b
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65534:65534
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65534:65534
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.PP
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65534 is the overflow id used when the UID/GID is not known inside the
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user namespace. This happens because both users 0:0 and 1:1 are not
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mapped.
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.PP
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In the above example, if we mount the fuse\-overlayfs file system using:
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\fB\fC\-ouidmapping=0:1000:1:1:110000:65536,gidmapping=0:1000:1:1:110000:65536\fR,
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which is the namespace configuration specified on a single line, we'd
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see from the same user namespace:
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.PP
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$ stat \-c %u:%g merged/a merged/b
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0:0
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1:1
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.PP
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Those are the same IDs visible from outside the user namespace.
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.SH SEE ALSO
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.PP
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\fBfuse\fP(8), \fBmount\fP(8), \fBuser\_namespaces\fP(7)
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.SH AVAILABILITY
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.PP
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The fuse\-overlayfs command is available from
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\fBhttps://github.com/containers/fuse\-overlayfs\fP under GNU GENERAL PUBLIC LICENSE Version 3 or later.
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