Linux – Building a disk image without root privileges

disk-imagelinux

I am attempting to setup nightly builds of a Linux OS on my webserver. Well, the problem is I need to generate a floppy disk image without being root.

Really, I don't need to fully generate it. I just need to update the image. As I have a FFS image with boot manager and such, and just need to add my kernel file to the image. I have seen no useful image tools out there though with dealing with FFS.

Does anyone know of some tools to use for updating such a floppy image. I wouldn't mind programming a little glue program, but I really don't want to code up full FFS support by myself at the moment.

Best Answer

I can offer two (non-ideal) options:

Create a 'placeholder' file inside your disk image and splice the kernel into the image (ick)
If you don't need to use FFS, you could try FAT. mtools is very handy for this sort of thing.

Example:

michael:~> mdir -i test.img ::
 Volume in drive : is Testing (abbr=TESTING    )
 Volume Serial Number is 0000-0000
Directory for ::/

No files
                          1 457 664 bytes free

michael:~> mcopy -i test.img kernel.com ::
michael:~> mdir -i test.img ::
 Volume in drive : is Testing (abbr=TESTING    )
 Volume Serial Number is 0000-0000
Directory for ::/

kernel   com     47632 2009-06-17  16:50 
        1 file               47 632 bytes
                          1 409 536 bytes free

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dd is most certainly the best cloning tool, it will create a 100% replica simply by using the following command. I've never once had any problems with it.

dd if=/dev/sda of=/dev/sdb bs=32M

Be aware that while cloning every byte, you should not use this on a drive or partition that is being used. Especially applications like databases can't cope with this very well and you might end up with corrupted data.

Linux – Simple One-Way Synchronization of User Password List Between Servers

You can use awk to extract users/groups with IDs of 500 or greater. I have also taken the liberty of excluding user id 65534, which is often reserved for the "nobody" user (depending on distro; no clue if CentOS does so):

awk -F: '($3>=500) && ($3!=65534)' /etc/passwd > passwd.new
awk -F: '($3>=500) && ($3!=65534)' /etc/group > group.new
awk -F: '($3>=500) && ($3!=65534) {print $1}' /etc/passwd | grep -f - /etc/shadow > shadow.new

Then use rsync, scp, or your file transmission method of choice to copy the files to your backup system. These files can then be appended to the end of a 'clean' passwd, group or shadow file when you need to restore them (ie: default system users/groups only, to prevent unintentional duplications of ID/username).

cat passwd.new >> /etc/passwd
cat group.new >> /etc/group
cat shadow.new >> /etc/shadow

Best Answer

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