Added usage tips for FreeBSD embedded

How-to-use-on-embedded-FreeBSD.md

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+FreeBSD embedded systems like nas4free, FreeNAS, pfSense etc. usually don't have curl and wget installed. The [fetch(1)](http://www.freebsd.org/cgi/man.cgi?fetch(1)) utility can't replace them, because it doesn't support POST and PUT requests. So I used this workaround to get curl running on this platform.
+
+Full story in Issue [#194](https://github.com/Neilpang/acme.sh/issues/194).
+
+## Requirements
+
+You need:
+
+* a persistent storage (to save some files)
+* your FreeBSD version and architecture (e.g. FreeBSD 10, x86-64)
+
+## 1. Find curl and ca-root-nss packages
+
+You need to get the curl binary and the ca-root-nss.crt containing trusted certificate authorities.
+
+Search for the packages in the download archives: [http://distcache.freebsd.org/](http://distcache.freebsd.org/)
+
+E.g., currently these would be for FreeBSD 10 x86-64:
+
+* http://distcache.freebsd.org/freebsd:10:x86:64/latest/All/curl-7.49.0.txz
+* http://distcache.freebsd.org/freebsd:10:x86:64/latest/All/ca_root_nss-3.22.2.txz
+
+## 2. Download and extract
+
+Replace the URLs found in step 1 above.
+
+```
+$ cd <path on your persistent storage> # e.g. nas4free: somewhere in /mnt/pool0
+$ fetch -o curl.txz http://distcache.freebsd.org/freebsd:10:x86:64/latest/All/curl-7.49.0.txz
+$ tar xvf curl.txz /usr/local/bin/curl
+$ mv usr/local/bin/curl .
+$ rm curl.txz
+$ fetch -o carootnss.txz http://distcache.freebsd.org/freebsd:10:x86:64/latest/All/ca_root_nss-3.22.2.txz
+$ tar xvf carootnss.txz /usr/local/share/certs/ca-root-nss.crt
+$ mv /usr/local/share/certs/ca-root-nss.crt .
+$ rm carootnss.txz
+$ # rm -r usr # be sure you're not in / ;-)
+```
+
+## 3. Configure your shell
+
+Your shell needs to know how to use the new curl binary. Create a file `_shell_profile` in same directory as above:
+
+`_shell_profile`:
+```
+export CURL_CA_BUNDLE=<path on your persistent storage>/ca-root-nss.crt
+export PATH=$PATH:<path on your persistent storage>
+```
+
+Load it in your current shell session:
+
+```
+$ . _shell_profile
+```
+
+## 4. Install acme.sh
+
+Now download and install acme.sh using the [advanced configuration](https://github.com/Neilpang/acme.sh/wiki/How-to-install#4-advanced-installation).
+
+```
+./acme.sh --install --home <path on your persistent storage>
+```
+
+You can now use it as usual.
+
+## 5. Certificate renewal with cronjob
+
+Usually, acme.sh can't create the automatic cronjob for certificate renewal on those platforms. I use a script like this:
+
+`acme-renew.sh`:
+```
+. <path on your persistent storage>/_shell_profile
+acme.sh --cron --home <path on your persistent storage>
+```
+
+Don't forget to `chmod +x acme-renew.sh`.
+
+Now find out how to create the cronjob on your system. For nas4free, you can do it in the web interface under **System -> Advanced -> Cron**. I scheduled it for running on the 1st of every month.