---
src/pylorax/ltmpl.py | 43 +++++++++++++++++++++++++++++++++++++++++--
1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/src/pylorax/ltmpl.py b/src/pylorax/ltmpl.py
index 7b5b29e..d3e05e3 100644
--- a/src/pylorax/ltmpl.py
+++ b/src/pylorax/ltmpl.py
@@ -96,10 +96,49 @@ def rglob(pathname, root="/", fatal=False):
def rexists(pathname, root=""):
return True if rglob(pathname, root) else False

-# XXX NOTE: symlinks to stuff outside inroot/outroot will make us operate
-# on files outside our roots (e.g. deleting files on the host system).
# TODO: operate inside an actual chroot for safety? Not that RPM bothers..
class LoraxTemplateRunner(object):
+ '
+ This class parses and executes Lorax templates. Sample usage:
+
+ # install a bunch of packages
+ runner = LoraxTemplateRunner(inroot=rundir, outroot=rundir, yum=yum_obj)
+ runner.run("install-packages.ltmpl")
+
+ # modify a runtime dir
+ runner = LoraxTemplateRunner(inroot=rundir, outroot=newrun)
+ runner.run("runtime-transmogrify.ltmpl")
+
+ NOTES:
+
+ * Parsing procedure is roughly:
+ 1. Mako template expansion (on the whole file)
+ 2. For each line of the result,
+ a. Whitespace splitting (using shlex.split())
+ b. Brace expansion (using brace_expand())
+ c. If the first token is the name of a function, call that function
+ with the rest of the line as arguments
+
+ * Parsing and execution are *separate* passes - so you can't use the result
+ of a command in an %if statement (or any other control statements)!
+
+ * Commands that run external programs (systemctl, gconfset) currently use
+ the *host*'s copy of that program, which may cause problems if there's a
+ big enough difference between the host and the image you're modifying.
+
+ * The commands are not executed under a real chroot, so absolute symlinks
+ will point *outside* the inroot/outroot. Be careful with symlinks!
+
+ ADDING NEW COMMANDS:
+
+ * Each template command is just a method of the LoraxTemplateRunner
+ object - so adding a new command is as easy as adding a new function.
+
+ * Each function gets arguments that correspond to the rest of the tokens
+ on that line (after word splitting and brace expansion)
+
+ * Commands should raise exceptions for errors - don't use sys.exit()
+ '
def __init__(self, inroot, outroot, yum=None, fatalerrors=True,
templatedir=None, defaults={}):
self.inroot = inroot
--
1.7.10.2

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