Command to rebuild all DKMS modules for all installed kernels?

I figured out a shell one-liner to do it:

ls /var/lib/initramfs-tools | \
    sudo xargs -n1 /usr/lib/dkms/dkms_autoinstaller start

This works because the names of the directories in /var/lib/initramfs-tools are exactly the kernel version names that you need to pass to dkms_autoinstaller to tell it to rebuild all modules for those kernel versions. Note that if you have uninstalled some old kernels, their directories might still be lying around and cause some errors to be reported, but this isn't a problem because dkms_autoinstaller will just do nothing for those kernel versions that aren't installed.

Doesn't look like the dkms command allows you to do that. I created a small Python script that should do what you want. You can put an alias in your ~/.bashrc like

alias dkms-buildall='sudo ./wherever/your/script/is'

Of course you'd need to make it executable first. Here's the code:

#!/bin/env python
#
# NOTE: This assumes that all modules and versions are built for at
#       least one kernel. If that's not the case, adapt parsing as needed.
import os
import subprocess

# Permission check.
if os.geteuid() != 0:
    print "You need to be root to run this script."
    exit(1)

# Get DKMS status output.
cmd = ['dkms', 'status']
process = subprocess.Popen(cmd, stdout=subprocess.PIPE)
dkms_status = process.communicate()[0].strip('\n').split('\n')
dkms_status = [x.split(', ') for x in dkms_status]

# Get kernel versions (probably crap).
cmd = ['ls', '/var/lib/initramfs-tools/']
# Alternative (for use with Arch Linux for example)
# cmd = ['ls', '/usr/lib/modules/']
process = subprocess.Popen(cmd, stdout=subprocess.PIPE)
kernels = process.communicate()[0].strip('\n').split('\n')

# Parse output, 'modules' will contain all modules pointing to a set
# of versions.
modules = {}

for entry in dkms_status:
   module = entry[0]
   version = entry[1].split(': ')[0]
   try:
      modules[module].add(version)
   except KeyError:
      # We don't have that module, add it.
      modules[module] = set([version])

# For each module, build all versions for all kernels.
for module in modules:
   for version in modules[module]:
      for kernel in kernels:
         cmd = ['dkms', 'build', '-m', module, '-v', version, '-k', kernel]
         ret = subprocess.call(cmd)

Tested it here, seems to work just fine:

$ dkms status
nvidia-current, 275.09.07, 3.0.0-5-generic, x86_64: installed
virtualbox, 4.0.10, 3.0.0-5-generic, x86_64: installed

$ sudo python dkms.py
...

$ dkms status
nvidia-current, 275.09.07, 3.0.0-5-generic, x86_64: installed
nvidia-current, 275.09.07, 3.0-2-generic, x86_64: built
nvidia-current, 275.09.07, 3.0-3-generic, x86_64: built
virtualbox, 4.0.10, 3.0.0-5-generic, x86_64: installed
virtualbox, 4.0.10, 3.0-2-generic, x86_64: built
virtualbox, 4.0.10, 3.0-3-generic, x86_64: built

If you also want to install the modules, replace build with install in the second last line.

Combining @htorque and @Ryan Thompson's answers, here's my (as root) one-liner:

dkms status | sed s/,//g | awk '{print "-m",$1,"-v",$2}' | while read line; do ls /var/lib/initramfs-tools | xargs -n 1 dkms install $line -k; done