Tuesday, September 11, 2012

Error messages

I love error messages, especially the ones that make you think that something else is wrong so you beat your head trying to bash the wrong thing into shape.

I spent quite a few hours trying to get a solaris jumpstart on a machine that is roughly 1200km from the jumpstart server to actually do the install.  This was a slow tedious process because the round trip time made everything take a long time.  The error I was getting was something like:

Error: Unable to create 9680Mb slice (unnamed)

and then a dump of the mbr and partition table of the disk in the machine.  Giving one the impression that somehow the solaris installer was objecting to the partitions/mbr currently on the disk.  No amount of clearing nor manually setting up of the partitions would make the error go away.

The real problem?  The fact that I had foolishly ASSuMEd that leaving the directive for creating a mirrored pool on a single disk machine would be harmless.... oh no.  What I think the error really meant was "you told me to make a mirror and I can't find another device to do that on".  It would have been nice if the error had been along the lines of "insufficient vdevs for mirror" or something along those lines.  After I removed the mirror option from the pool setup directive the error went away... *sigh*.

Monday, September 10, 2012

NetBSD on a stick

This is not really a new idea but after a couple of upgrade "oopses" that rendered my machine unbootable due to init getting upset about not finding MAKEDEV I decided I needed a safety net that was a little bit more portable than the USB hard disk enclosure that had saved me in the past.

I had a spare 4Gb USB memory stick which is more than ample to hold a full NetBSD install including X and a few other bits and pieces so I decided to put the memory stick to good use.  The advantage of using a memory stick is that it is easy to update, we have the entire NetBSD toolset available, not some cut down version.  The downside is that the memory stick does have a limited number of writes so one wouldn't last very long for full time day to day use but as a portable rescue device or even just to be used to test new hardware before buying it can be useful.

On my laptop the memory stick appeared as sd0 so I will use this device in all my examples, for those following along at home you may need to adjust your device naming.

Firstly, I needed to adjust the mbr.  The memory stick had a single MSDOS partition on it, this needed to be changed to be a NetBSD one (type 169).  To do this I ran fdisk:

fdisk -u /dev/sd0d

The -u flag makes fdisk interactive, prompting you to update certain parameters as you go along.  For my purposes I just accepted the defaults to everything until I was prompted to change a partition.  At this point I just selected the only partition there and changed the sysid to 169 and set a bootmenu label of NetBSD, all other parameters were left at their default.  Once I had finished editing the partitions I accepted the default "none" at the partition prompt to move on.  Fdisk prompted me to update the mbr to which I said yes and also said yes to it updating the mbr type to bootsel since I had a boot menu.

Once the mbr was set it was time to edit the disklabel:

disklabel -e /dev/sd0d

This opens up the disk label in an editor.  I left most of the settings as is only editing the e: partition, I changed the e: into an a: and change the fstype to "4.2BSD", set the fsize to 2048, the pgsize to 16384 and the cpg/sgs to 0.  The line ended up looking like:

  a:   7883696      1104     4.2BSD   2048 16384     0  # (Cyl.      0*-   3849)

Then I just saved the changes and quit the editor.  With the new disklabel in place I could then create the filesystem:

newfs /dev/sd0a

This took a while to do but eventually completed without problem.  Once the file system was built I mounted it:

mount /dev/sd0a /mnt

Then unpacked the installation sets onto the memory stick.  I had created my own release files using "build.sh release" but I could have easily just downloaded the official sets, the files I needed were under the binary/sets directory.  I just cd'ed to that directory and did:

for f in *.tgz
 (cd /mnt && tar zxpf ${cdir}/${f})

and waited for a long time, the unpacking was very slow.  Once this was done I picked the kernel-GENERIC.gz file from binary/kernel, uncompressed this and copied as /mnt/netbsd.

To make the memory stick bootable I did:

cp /usr/mdec/boot
installboot -fv /dev/sd0d /usr/mdec/bootxx_ffsv1

I had to use the -f flag on installboot because I was getting an error "Old BPB too big", the -f flag forced installboot to continue anyway, the result seemed to work fine.

I created a new fstab:

 /dev/sd0a       /               ffs     rw,log  1 1 

and edited /mnt/etc/rc.conf to change "rc_configured" to "YES" so the machine would come up multiuser.

After this it was just a matter of rebooting my machine, the BIOS picked up a USB device and started a boot from it.  I was presented with a boot menu, when I selected the only option my machine slowly booted from the memory stick.  I was able to log in and do everything you would expect to be able to do on a clean NetBSD install.