shr – global mountpoints

bind '#σ' /shr

The shr device provides global mountpoints in the form of share directories where 9P services can be mounted.
Effectively, it is a global mountpoint registry that is separate from private namespaces.

The shr device exports a mount tree and a control tree. The directories in the mount tree are the share mountpoints themselves, while the directories in #σc contain the service files of the share.

To create a new share, create the directory #σc/myshare
To mount a service in that share, create the file #σc/myshare/myserv and then write a text string (suitable for strtoul; see atof(2)) giving the file descriptor number of an open 9P service. Any process with the proper permission may then access #σ/myshare on the mount tree.

The service file can be reopened and passed to mount (see bind(2)) or added to another share.

Multiple services can be mounted under a share forming a union directory. New services get mounted before old ones. Removing the service file unmounts the service from the share.

Creating shares and mounts requires read–write access in the share directory. The special user none is prohibited from these operations.

To mount a 9p service from srv(3) to the shr device
mkdir '#σc'/myshare
echo 3 > '#σc'/myshare/myserv <>[3]/srv/myserv


Shr first appeared in 9front (July, 2011).