Installing grub on removable media

Grub is a really nifty boot loader. I especially love two things about it:

• A command-line interface
• No reinstallation for kernel changes

Even if the OS boot loader gets knackered, you can probably restore it if you have a grub floppy.

Installing grub on a floppy
Here's how to get grub on a floppy:

• Kiss the prior contents of the floppy goodbye ;-)
• Change to the directory /usr/share/grub/i386-redhat (on fedora) or /usr/lib/grub (on Suse) or /usr/share/grub/i386-pc if you built and installed grub yourself
  
• Execute the commands:
dd if=stage1 of=/dev/fd0 bs=512 count=1
dd if=stage2 of=/dev/fd0 bs=512 seek=1


You ought to be able to get a grub prompt on booting with this disk.

Here's another way to do the same thing - not so destructively

• Mount a ext2-formatted floppy to say /mnt/floppy
• Copy the contents of the /usr/share/grub/i386*/{stage1,stage2,e2fs_stage1_5} to /mnt/floppy/boot/
• Optionally create a /mnt/floppy/boot/menu.lst
• Execute grub-install --root-directory=/mnt/floppy fd0
• Umount the floppy

If you dont have grub-install, or are paranoid about using it, there's yet another way - boot into a grub prompt either using a floppy created using the destructive way outlined above, or on some machine with grub installed on the hard disk. Drop to a grub prompt. Then place the ext2 floppy in the drive and execute:
root (fd0)
setup (fd0)
You ought to have a grub-bootable on your hands now. I think the grub-install part ought to work with USB drives as well tho' I haven't really tried it.

Installing grub on a CD

• mkdir -p iso/boot/grub
• cp /usr/share/grub/i386-*/stage2_eltorito iso/boot/grub
• Optionally create a iso/boot/grub/menu.lst.
• Create an iso image:
  mkisofs -R -b boot/grub/stage2_eltorito -no-emul-boot \
  -boot-load-size 4 -boot-info-table -o grub.iso iso
• Burn the grub.iso image to cd.

Hopefully if all goes right, you have a bootable grub CD. Of course, try this with rewriteable CDs if you *really* need to be sure :)

Unzipping large files in Linux

Infozip's Unzip program has certain file size limits. It may not support files whose unzipped size is larger than 4GB and instead produce this error:
skipping: yeas3/yeas3.TRC need PK compat. v4.5 (can do v2.1)
Support for unzipping large files will come with Unzip 6.x - the current version is 5.52.
So what if you want to unzip a large file on unix *now*? You could either unzip on Windows with any number of utilities (7-zip/PowerArchiver/Izarc) and somehow get the file over to Linux/Unix - or locate the unix version of 7-zip's command line utility (7za) called p7zip. All you need to do is build the executable from source:
make
make install
Then run:
7za x file.zip [filename ...]
Till unzip 6.0 arrives, this one is going to be one fixture on my machine.