warning: really long post with some questions and thinking.
Hello dear OpenBSD types.
I have been using UNIX in various forms and flavours for a long time now
and could even go so far as to say a "very" long time. Therefore it just
seems so very familiar to me and yet, a bit new.
First thing I see is that it was so very easy to install. I was almost
expecting to need to curse and recurse but the install was trivial. I
kept a log of the whole process in case something went wrong but nope,
it is just a nice simple log.
However upon first boot I see that my disk slices are a bit odd in terms
of size. I would have liked to arrange things differently. Certainly I
will need to create a mount point for a /opt filesystem and that means I
need to read fdisk and disklabel man pages over and over.
The questions on my mind, in order of importance seem to be :
1) how do I do a full low level backup and then verify that I
can restore the system ? To an NFS mount or tape or whatever.
2) how do I edit the disk slices or "partitions" to be what I want?
3) how do I eventually contribute software packages or similar?
So number (1) would seem to need a dump command and I see a lot of very
friendly and familiar looking goodness in dump(8). The disk low level
bits seem to use 512 byte blocks and so I am going to guess that I can
do a level 0 dump of each filesystem one at a time to some NFS mounted
location and that would suffice for the filesystem level. Not too sure
how to deal with the partition table and boot records etc. I see from
the fdisk command this :
# fdisk -e sd0
Enter 'help' for information
fdisk: 1> print
Disk: sd0 geometry: 7508/19/248 [35378533 Sectors]
Offset: 0 Signature: 0xD6BC
Starting Ending LBA Info:
#: id C H S - C H S [ start: size ]
-------------------------------------------------------------------------------
0: 55 64103 7 97 - 64111 12 157 [ 302055168: 38997 ] EZ-Drive
1: D5 103269 3 18 - 103270 17 37 [ 486604289: 8204 ] <Unknown ID>
2: 92 153115 15 134 - 153118 17 75 [ 721481733: 14574 ] <Unknown ID>
3: 86 338260 4 10 - 106301 12 65 [ 1593882121: 3201978528 ] NT FAT VS
fdisk: 1> exit
Looks like there is some black magix at work in partition id 0 through
2 and then one big fat large chunk at id 3 wherein my OpenBSD 5.4 install
must live. I am not too sure how to dump or backup the partition table
info such that a totally blank disk could be inserted and then a restore
done. Perhaps my whole thinking appoach here is old school wrong?
Whatever the case the disklabel tool shows me this :
# disklabel sd0
# /dev/rsd0c:
type: SCSI
disk: SCSI disk
label: ST318404LSUN18G
duid: c5cd4c19ed688052
flags: vendor
bytes/sector: 512
sectors/track: 248
tracks/cylinder: 19
sectors/cylinder: 4712
cylinders: 7508
total sectors: 35378533
boundstart: 0
boundend: 35378533
drivedata: 0
16 partitions:
# size offset fstype [fsize bsize cpg]
a: 1201560 0 4.2BSD 2048 16384 1 # /
b: 1201560 1201560 swap # none
c: 35378533 0 unused
d: 1903648 2403120 4.2BSD 2048 16384 1 # /tmp
e: 2855472 4306768 4.2BSD 2048 16384 1 # /var
f: 2879032 7162240 4.2BSD 2048 16384 1 # /usr
g: 1672760 10041272 4.2BSD 2048 16384 1 # /usr/X11R6
h: 6266960 11714032 4.2BSD 2048 16384 1 # /usr/local
i: 2511496 17980992 4.2BSD 2048 16384 1 # /usr/src
j: 3491592 20492488 4.2BSD 2048 16384 1 # /usr/obj
k: 11393616 23984080 4.2BSD 2048 16384 1 # /home
#
So that tells me I have 35378533 blocks ( at 512 bytes each ) stuffed in
the big magic partition id 3 and that sd0:c ( correct notation? ) is
what we old Solaris/SunOS types would call the overlap slice. Seems to
make sense by the numbers :
# bc
35378533 * 512
18113808896
Yep, that is an old 18G disk there. However the word "partition" has me
wondering if I am looking at a "partition" table or a disk label. Not
entirely clear .. yet. The disklabel(5) man page sheds a bit of light
and the three disklabel.h headers shed even more :
# ls -l /usr/include/dev/sun/disklabel.h /usr/include/sparc64/disklabel.h \
> /usr/include/sys/disklabel.h
-r--r--r-- 1 root bin 4706 Apr 25 2010 /usr/include/dev/sun/disklabel.h
-r--r--r-- 1 root bin 2016 Jun 20 2007 /usr/include/sparc64/disklabel.h
-r--r--r-- 1 root bin 15300 Jun 11 2013 /usr/include/sys/disklabel.h
#
So really I don't see where the data from fdisk lives and I am getting
mixed up between "MBR partition table" data and the disklabel. At the
very least I don't yet see where those id numbers 55, D5, 92 and 86 come
from. Certainly when fdisk(8) says :
id MBR partition type identifier. OpenBSD reserves the magic
number hexadecimal A6 (166 decimal).
Well I don't have an 0xa6h anywhere. I have 0x86h which seems to be one
bit away from 0xa6h == 1010 0110b. So maybe the bit 5 has some special
value here. Not sure. Anyways, I don't know where the MBR boot record
data lives but I am guessing sector 0 on track/cylinder zero of the disk.
The real problem on my mind is how to take /dev/sd0k and break it up a
bit. I didn't want a 5.3GB /home :
# df -h
Filesystem Size Used Avail Capacity Mounted on
/dev/sd0a 575M 116M 431M 21% /
/dev/sd0k 5.3G 40.0K 5.1G 0% /home
/dev/sd0d 914M 8.0K 868M 0% /tmp
/dev/sd0f 1.4G 420M 895M 32% /usr
/dev/sd0g 801M 139M 622M 18% /usr/X11R6
/dev/sd0h 2.9G 104M 2.7G 4% /usr/local
/dev/sd0j 1.6G 2.0K 1.6G 0% /usr/obj
/dev/sd0i 1.2G 2.0K 1.1G 0% /usr/src
/dev/sd0e 1.3G 9.3M 1.3G 1% /var
thor-int:/export/boot 35.4G 15.4G 20.0G 43% /mnt/thor
There seems to be plenty of room left over for a "partition" or "slice"
or thingy which allows /home to be 1GB and then a /opt created with 4GB
or so at /dev/sd0l ( the letter ell ).
So is there a webpage somewhere that may explain some of the inner bits
I am seeing? The page at http://www.openbsd.org/faq/faq14.html seems a
bit glossy on the topic of how to wrangle these label bits.
Dennis
ps: as for dump and backup .. I can figure that out but really how to
sort out the disk MBR record and partition table and slice or label
bits seems more important first.
