diff options
2 files changed, 81 insertions, 4 deletions
diff --git a/doc/forum/imageBuiltFor_mount_points_not_automatically_created/comment_7_ad9ea2799890df2dfce4f0cc99e397e9/comment_1_68b3d9ca04283c2400f5b23e486bb4b7._comment b/doc/forum/imageBuiltFor_mount_points_not_automatically_created/comment_7_ad9ea2799890df2dfce4f0cc99e397e9/comment_1_68b3d9ca04283c2400f5b23e486bb4b7._comment new file mode 100644 index 00000000..c7d7e384 --- /dev/null +++ b/doc/forum/imageBuiltFor_mount_points_not_automatically_created/comment_7_ad9ea2799890df2dfce4f0cc99e397e9/comment_1_68b3d9ca04283c2400f5b23e486bb4b7._comment @@ -0,0 +1,62 @@ +[[!comment format=mdwn + username="joey" + subject="""comment 1""" + date="2017-12-21T19:44:45Z" + content=""" +Reproduced it with that information. + + ghci> calcPartedParamsSize guexPartTable + (["mklabel","gpt","mkpart","primary","fat32","4194304B","16777215B","set","1","esp","on","mkpart","primary","ext2","16777216B","167772159B","mkpart","primary","ext4","167772160B","1660944383B"],1660944384) + 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. +"""]] diff --git a/src/Propellor/Property/Parted.hs b/src/Propellor/Property/Parted.hs index 38c55b93..be12933d 100644 --- a/src/Propellor/Property/Parted.hs +++ b/src/Propellor/Property/Parted.hs @@ -85,8 +85,8 @@ calcPartedParamsSize (PartTable tabletype alignment parts) = [ "mkpart" , pval (partType p) , pval (partFs p) - , partpos startpos - , partpos endpos + , partposexact startpos + , partposfuzzy endpos ] ++ case partName p of Just n -> ["name", show partnum, n] Nothing -> [] @@ -95,14 +95,29 @@ calcPartedParamsSize (PartTable tabletype alignment parts) = in calcparts (partnum+1) endpos ps (c ++ mkpart partnum startpos (endpos-1) p : map (mkflag partnum) (partFlags p)) calcparts _ endpos [] c = (c, endpos) - partpos n - | n > 0 = val n ++ "B" + + -- Exact partition position value for parted. + -- For alignment to work, the start of a partition must be + -- specified exactly. + partposexact n + | n > 0 = show n ++ "B" -- parted can't make partitions smaller than 1MB; -- avoid failure in edge cases | otherwise = "1MB" + + -- Fuzzy partition position valie for parted. + -- This is used to specify the end of the partition, + -- parted takes the "MB" as license to slightly reduce the + -- partition size when something about the partition table + -- does not allow the partition to end exactly at the position. + partposfuzzy n + | n > 0 = show (fromIntegral n / 1000000) ++ "MB" + | otherwise = "1MB" + -- Location of the start of the first partition, -- leaving space for the partition table, and aligning. firstpos = align partitionTableOverhead + align = alignTo alignment -- | Runs parted on a disk with the specified parameters. |