salt-minion/README.md: Discuss minion caching and sync_all

I needed the explicit sync_all with Salt v0.17.0.  It's possible that
this is a bug that has been (or will be) fixed in future versions.

diff --git a/salt-minion/README.md b/salt-minion/README.md
index 69263fbc624c12dfde81badb1edfb8c8014a3d5b..8a0e8a858ba27ac41e501e988df2dde9ba340d37 100644 (file)
--- a/salt-minion/README.md
+++ b/salt-minion/README.md
@@ -6,6 +6,9 @@ The [default master name][master-name] is `salt`, so make sure that
 resolves appropriately on your Docker host (via DNS or an entry in
 `/etc/hosts`).
 
+Minion keys
+===========
+
 You have two options for setting up minon keys.  The more secure
 approach is to create and install minion keys on the master:
 
@@ -26,8 +29,35 @@ mount][volume-mount]:
 The less secure approach is to [auto-accept][] the minion's
 internally-generated key.
 
+Minion caching
+==============
+
+If you blow away a minion container and replace it with a
+freshly-spawned container, you may get errors in the minion logs like:
+
+    Feb 25 20:14:18 salt-minion-0 2014-02-25 20:14:18,257 [salt.fileclient  ][INFO    ] Fetching file ** done ** 'elasticsearch/init.sls'
+    Feb 25 20:14:18 salt-minion-0 2014-02-25 20:14:18,289 [salt.state       ][INFO    ] Executing state file.managed for /etc/portage/package.use/elasticsearch
+    Feb 25 20:14:18 salt-minion-0 2014-02-25 20:14:18,396 [salt.fileclient  ][INFO    ] Fetching file ** done ** 'elasticsearch/files/gentoo/package.use'
+    Feb 25 20:14:18 salt-minion-0 2014-02-25 20:14:18,402 [salt.state       ][ERROR   ] An exception occurred in this state: Traceback (most recent call last):
+      File "/usr/lib64/python2.7/site-packages/salt/state.py", line 1305, in call
+        *cdata['args'], **cdata['kwargs'])
+      File "/usr/lib64/python2.7/site-packages/salt/states/file.py", line 1157, in managed
+        dir_mode)
+      File "/usr/lib64/python2.7/site-packages/salt/modules/file.py", line 2150, in manage_file
+        __opts__['cachedir'])
+      File "/usr/lib64/python2.7/site-packages/salt/utils/__init__.py", line 599, in copyfile
+        '[Errno 2] No such file or directory: {0}'.format(source)
+    IOError: [Errno 2] No such file or directory: /var/cache/salt/minion/files/base/elasticsearch/files/gentoo/package.use
+
+That's because the master expects the salt state to be cached on the
+old container.  To fill in the cache on the new container, you'll want
+to [manually sync][sync_all] the minion:
+
+    salt# salt salt-minion-0 saltutil.sync_all
+
 [salt]: http://saltstack.com/community.html
 [master-name]: http://docs.saltstack.com/ref/configuration/minion.html#master
 [preseed]: http://docs.saltstack.com/topics/tutorials/preseed_key.html
 [volume-mount]: http://docs.docker.io/en/latest/use/working_with_volumes/
 [auto-accept]: http://docs.saltstack.com/ref/configuration/master.html#auto-accept
+[sync_all]: http://docs.saltstack.com/ref/modules/all/salt.modules.saltutil.html#salt.modules.saltutil.sync_all