Persistent change files for live-CD distros, how to manage.

digby · 01-24-2009, 12:48 PM

Slax, Knoppix, Puppy and other live CD distros allow users to save their changes beyond the next boot to a "change file". These files are a pre-decided fixed-size, and are formatted as linux file systems. My first question is how can one find out the amount of space within these files that is actually being used? Then, armed with this information, how can one enlarge or shrink the size of the change file (as needed)?

mrclisdue · 01-24-2009, 02:25 PM

Not sure where you get the impression that these files are "a pre-decided fixed size." I run slax off of a usb stick, and the "change file" is actually a directory on the usb stick which increases (or decreases) according to the changes.

In the case of a live-cd, you would indicate what directory on your hard drive (or whatever device) the changes would be saved to, and as long as there is room in that particular directory, you're fine.

From linux-live.org (by the same dude responsible for slax) :

Quote:

Interesting features of Linux Live scripts

1)
persistent changes

Use 'changes=...' boot parameter to specify persistent changes directory or file. If a directory is used, eg. changes=/some_dir/ and the /some_dir/ is found on some partition on your disk, then all the changes made to the root filesystem will be saved to that directory. This works even if /some_dir/ is on NTFS or VFAT, thanks to posixovl overlay (an userspace filesystem, already included). Important note: if you plan to save changes on VFAT, make sure to modify your distribution's shutdown scripts. It must not execute killall, else posixovl is killed and everything is wrong. Instead, call the cleanup script from /mnt/live/cleanup. If a file is specified for the changes boot parameter, eg. changes=/path/file.dat, and the file has a valid filesystem inside, then the file will be loop-mounted and changes written to it. You may also use changes=/dev/sda1/path/ and changes=/dev/sda1/path/file.dat ... to specify particular device where to look for. Other devices will be skipped (will not be even mounted).

cheers,

digby · 01-24-2009, 03:36 PM

Thanks for your reply. I use 'changes=/mnt/hda6/slaxsave.dat' to store my changes. It has worked beautifully for months. The amount of information on it, indeed, must rise and fall with continuing usage. My question involves the slaxsave.dat file, which is what I believe you call,the directory. I did indeed create it to my pre-decided fixed size of .5GB. I would like to know how much space in the directory is actually utilized at any particular time. (FWIW, I used 'puppy firehydrant' before Slax and it gave me my answer via the conky utility. But now I greatly prefer Slax which doesn't.) I would also like to know how to change the size of the directory, slaxsave, without losing data. Perhaps, there are bash commands that can do this?