From e9ea0f758b0cba3febe27c91fced9825b94e3c9b Mon Sep 17 00:00:00 2001 From: Giuseppe Scrivano Date: Fri, 29 Mar 2019 10:23:57 +0100 Subject: [PATCH] fuse-overlayfs.1: regenerate Signed-off-by: Giuseppe Scrivano --- fuse-overlayfs.1 | 68 +++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 67 insertions(+), 1 deletion(-) diff --git a/fuse-overlayfs.1 b/fuse-overlayfs.1 index 5b99f40..39f3677 100644 --- a/fuse-overlayfs.1 +++ b/fuse-overlayfs.1 @@ -23,6 +23,10 @@ namespace. .SH OPTIONS +.PP +\fB\-\-debug\fP +Enable debugging mode, can be very noisy. + .PP \fB\-o lowerdir=low1[:low2...]\fP A list of directories separated by \fB\fC:\fR\&. Their content is merged. @@ -37,10 +41,72 @@ done to the file system will be written. A directory used internally by fuse\-overlays, must be on the same file system as the upper dir. +.PP +\fB\-o workdir=workdir\fP +A directory used internally by fuse\-overlays, must be on the same file +system as the upper dir. + +.PP +\fB\-o uidmapping=UID:MAPPED\-UID:LEN[,UID2:MAPPED\-UID2:LEN2]\fP +\fB\-o gidmapping=GID:MAPPED\-GID:LEN[,GID2:MAPPED\-GID2:LEN2]\fP +Specifies the dynamic UID/GID mapping used by fuse\-overlayfs when +reading/writing files to the system. + +.PP +The fuse\-overlayfs dynamic mapping is an alternative and cheaper way +to chown'ing the files on the host to accomodate the user namespace +settings. + +.PP +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. + +.PP +For example, given on the host two files like: + +.PP +$ stat \-c %u:%g lower/a lower/b +0:0 +1:1 + +.PP +When we run in a user namespace with the following configuration: +$ cat /proc/self/uid\_map + 0 1000 1 + 1 110000 65536 + +.PP +We would see: + +.PP +$ stat \-c %u:%g merged/a merged/b +65534:65534 +65534:65534 + +.PP +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. + +.PP +In the above example, if we mount the fuse\-overlayfs file system using: +\fB\fC\-ouidmapping=0:1000:1:1:110000:65536,gidmapping=0:1000:1:1:110000:65536\fR, +which is the namespace configuration specified on a single line, we'd +see from the same user namespace: + +.PP +$ stat \-c %u:%g merged/a merged/b +0:0 +1:1 + +.PP +Those are the same IDs visible from outside the user namespace. + .SH SEE ALSO .PP -\fBfuse\fP(8), \fBmount\fP(8) +\fBfuse\fP(8), \fBmount\fP(8), \fBuser\_namespaces\fP(7) .SH AVAILABILITY