|author||Joey Hess||2017-12-21 17:02:26 -0400|
|committer||Joey Hess||2017-12-21 17:02:26 -0400|
Diffstat (limited to 'doc/forum/imageBuiltFor_mount_points_not_automatically_created/comment_9_68b3d9ca04283c2400f5b23e486bb4b7._comment')
1 files changed, 62 insertions, 0 deletions
diff --git a/doc/forum/imageBuiltFor_mount_points_not_automatically_created/comment_9_68b3d9ca04283c2400f5b23e486bb4b7._comment b/doc/forum/imageBuiltFor_mount_points_not_automatically_created/comment_9_68b3d9ca04283c2400f5b23e486bb4b7._comment
new file mode 100644
@@ -0,0 +1,62 @@
+ subject="""comment 1"""
+Reproduced it with that information.
+ ghci> calcPartedParamsSize guexPartTable
+ joey@darkstar:~>dd if=/dev/zero of=test bs=1M count=1584
+ joey@darkstar:~>parted test
+ (parted) p
+ Model: (file)
+ Disk /home/joey/test: 1661MB
+ Sector size (logical/physical): 512B/512B
+ (parted) mklabel gpt
+ (parted) mkpart primary fat32 4194304B 16777215B
+ (parted) mkpart primary ext2 16777216B 167772159B
+ (parted) mkpart primary ext4 167772160B 1660944383B
+ Warning: You requested a partition from 168MB to 1661MB (sectors 327680..3244031).
+ The closest location we can manage is 168MB to 1661MB (sectors 327680..3243998).
+The problem only occurs with the gpt partition table. With "mklabel msdos",
+the mkpart command succeeds.
+So, gpt must have an additional restriction
+of some kind. I don't know what. The highest end position that parted
+will accept for that partition is 1660927487B; slightly smaller partitions
+are accepted. It's not a requirement that the position or size be divisible
+by anything in particular. Perhaps gpt needs some amount of reserved space
+at the end of the disk or something.
+Before 4MiB alignment was added, here's what
+propellor did for the same PartTable, which worked.
+ mkpart primary ext4 160MB 1649MB
+It would be good for propellor to not need to know about all the minutia of
+partition tables. Seems that the way it used to call parted gave it enough
+wiggle room that it avoided this kind of problem.
+To make parititions well aligned, propellor needs to precisely control where
+they begin (since parted does not have a way to configure modern
+alignment requirments). Perhaps propellor could precisely specify where a
+partition begins, but use the "MB" to leave wiggle room in where it ends
+so parted can pick a suitable end point.
+Let's see.. this works with the gpt example:
+ (parted) mkpart primary fat32 4194304B 16.777215MB
+ (parted) mkpart primary ext2 16777216B 167.772159MB
+ (parted) mkpart primary ext4 167772160B 660.944383MB
+That lets parted end the last partition right at the ideal 1660927487B.
+The previous two partitions end right where propellor expects.
+(Hopefully parted never rounds a MB value *up*!)
+Ok, I've convinced myself to make propellor use this wacky technique
+of B for the start position and fractional MB for the end position!
+I've implemented it, hopefully my analysis above is good to make
+this work with all the different kinds of partition tables.