New Core Storage blog post

input/blog/2015/2015_08_06_core_storage.md

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+title: Blog
+post: Core Storage Partition resizing
+date: 2015-08-06
+comments: true
+flattr: true
+twitter: xythobuz
+---
+
+## {{ page["post"] }}
+<!--%
+from datetime import datetime
+date = datetime.strptime(page["date"], "%Y-%m-%d").strftime("%B %d, %Y")
+print "*Posted at %s.*" % date
+%-->
+
+Basically, Disk Utility in Yosemite started using Core Storage sometimes when creating new partitions. Unfortunately, if it then encounters a Core Storage Volume, it completely shits its pants and doesn’t do anything anymore.
+
+Presumably, this will be fixed in the next release, El Capitan.
+
+In the meantime, some command line diskutil Foo is required to fix your partition map when Disk Utility does no longer want to do this.
+
+In my case, I wanted to shrink a Core Storage Logical Volume, to make room for a new NTFS partition shared between Mac and Windows. Of course, Windows can’t read the Core Storage Volume, and NTFS inside Core Storage is not even possible anyways.
+
+So, I needed to shrink the volume and add a new one. Between the steps, I tried again and again to use Disk Utility, but it only fucked up things more. So keep it closed and stay with diskutil.
+
+In the end, I had to do something like the following. diskN is the physical disk where everything was located, and diskNsX is the newly created partition.
+
+    diskutil list
+    diskutil cs list
+    
+    diskutil unmountDisk diskN
+
+Sometimes it seems to be possible to revert a Core Storage Volume, so you can go back to Disk Utility. However, this was not possible with my partition. So I continued like this:
+
+    diskutil cs resizeStack LVUUID partsize
+    sudo gpt -r show diskN
+
+Then find the start sector of the newly freed space, substract 262144 (= 128MiB) from size (Apple required padding between partitions), and use these numbers for your new partition (yours will differ!):
+
+    sudo gpt add -b 1700605768 -s 1698790088 -t windows diskN
+    sudo newfs_exfat -v "Shared" /dev/rdiskNsX
+    diskutil repairDisk diskN
+    for all partitions: diskutil repairVolume diskNsX
+
+And that’s it. Not as bad as it seemed.
+