Example: GForce

A Layer 3 example that forces a directory tree to be read/writeable by a group.

{% highlight lua %}

-- User configuration file for lsyncd.

-- This example refers to a common problem in unix.

-- You have a shared directory for a set of users and you want -- to ensure all users have read and write permissions on all -- files in there. Unfortunally sometimes users mess with their -- umask, and create files in there that are not read/write/deleteable -- by others. Usually this involves frequent handfixes by a sysadmin, -- or a cron job that recursively chmods/chowns the whole directory.

-- This is another approach to use lsyncd to continously fix permissions.

-- One second after a file is created/modified it checks for its permissions -- and forces group permissions on it.

-- This example regards more the handcraft of bash scripting than lsyncd. -- An alternative to this would be to load a Lua-Posix library and do the -- permission changes right within the onAction handlers.

---

-- forces this group.

fgroup = "staff"

---

-- script for all changes.

command = -- checks if the group is the one enforced and sets them if not '[[ perm=stat -c %A ^sourcePathname if test stat -c %G ^sourcePathname != ]]..fgroup..'[[; then /bin/chgrp ]]..fgroup..'[[ ^sourcePathname || /bin/true; fi ]] ..

-- checks if the group permissions are rw and sets them '[[ if test expr match $perm "....rw" = 0; then /bin/chmod g+rw ^sourcePathname || /bin/true; fi ]] ..

-- and forces the executable bit for directories. '[[ if test -d ^sourcePathname; then if test expr match $perm "......x" -eq 0; then /bin/chmod g+x ^^sourcePathname || /bin/true; fi fi ]]

-- on startup recursively sets all group ownerships -- all group permissions are set to 'rw' -- and to executable flag for directories

-- the hash in the first line is important, otherwise due to the starting -- slash, Lsyncd would think it is a call to the binary /bin/chgrp only -- and would optimize the shell call away.

startup = '[[# /bin/chgrp -R ]]..fgroup..'[[ ^source || /bin/true && /bin/chmod -R g+rw ^source || /bin/true && /usr/bin/find ^source -type d | xargs chmod g+x ]]

gforce = { maxProcesses = 99, delay = 1, onStartup = startup, onAttrib = command, onCreate = command, onModify = command, -- does nothing on moves, they won't change permissions onMove = true, }

sync{gforce, source="/path/to/share"} {% endhighlight %}