Changing a sun from multiple partitions on a disk to just one

Initial partitioning:

partition> print
Current partition table (original):
Total disk cylinders available: 14087 + 2 (reserved cylinders)

Part      Tag    Flag     Cylinders         Size            Blocks
  0       root    wm     104 -   544        2.14GB    (441/0/0)     4487616
  1        var    wm     545 -   559       74.53MB    (15/0/0)       152640
  2     backup    wm       0 - 14086       68.35GB    (14087/0/0) 143349312
  3       swap    wu       0 -   103      516.75MB    (104/0/0)     1058304
  4 unassigned    wm       0                0         (0/0/0)             0
  5 unassigned    wm     560 -   566       34.78MB    (7/0/0)         71232
  6 unassigned    wm       0                0         (0/0/0)             0
  7       home    wm     567 - 14086       65.60GB    (13520/0/0) 137579520

From memory, for first partition - merging /var into /:

mkdir /newvar

copy /var to /newvar

comment out /var on /etc/vfstab 

umount /var

rmdir /var

mv /newvar /var

reboot

In sun format:
Note the end cylinder of the /var partition
delete /var partition (EG, just make it start at cyl 0 and 0 cyls long,
so it's clear it isn't used for anything)
Redefine the / partition to end at the same end cylinder /var used to
have, using, in this case, 559e (e is a "unit" for the end cylinder of
a partition)

After the reboot, I get:

partition> print
Current partition table (original):
Total disk cylinders available: 14087 + 2 (reserved cylinders)

Part      Tag    Flag     Cylinders         Size            Blocks
  0       root    wm     104 -   559        2.21GB    (456/0/0)     4640256
  1 unassigned    wm       0                0         (0/0/0)             0
  2     backup    wm       0 - 14086       68.35GB    (14087/0/0) 143349312
  3       swap    wu       0 -   103      516.75MB    (104/0/0)     1058304
  4 unassigned    wm       0                0         (0/0/0)             0
  5 unassigned    wm     560 -   566       34.78MB    (7/0/0)         71232
  6 unassigned    wm       0                0         (0/0/0)             0
  7       home    wm     567 - 14086       65.60GB    (13520/0/0) 137579520

If you can get all the processes using a filesystem to go away, the
reboots are unnecessary - just umount

If swap is in between two partitions you want to merge, you'll probably
want to configure away swap in /etc/vfstab, reboot, merge swap, merge some
more if needed, then carve off some space for swap at the end.  But, in my
case, swap was actually at the beginning of the disk - yours might be too

As needed:

growfs -M / /dev/rdsk/c1t0d0s0

Be prepared for it to take a long time.  Just a guess, but it's probably
preallocating a bunch of inodes to preserve the previous inode to data
block ratio.

Be sure to use the raw device (rdsk), not the cooked device (dsk).

You may have to change /'s mount options (in /etc/vfstab, or possibly
via mount -o remount) to not have logging, with the "nologging" option,
instead of "-" or whatever.

My growfs final didn't complete, even though I left it running overnight.
The manual page says to speed up the process by running a bunch of
growfs's with the -s option :(

In some or all cases, you will need to boot from external media (CD,
NFS, perhaps another disk) in order to do the final grow, because in some
cases at least, the root filesystem cannot be grown while it is mounted