Disk Tips

To save space in your CIS Unix directory:

1. First, know what you can safely delete (not all of these items will apply to all users):
   • Old text files (including old mail folders) that aren't in active use might be better off on paper than on disk; print them, then delete.
   • It doesn't make much sense to use the Unix systems to store PC/Mac programs or PC/Mac-only datafiles that you've downloaded from an FTP site or received in e-mail; transfer them to your PC or Mac (if you haven't already done so), then delete them.
   • Executable files produced from C/Fortran/Pascal/etc compilers are typically quite big. You can get these back anytime by just recompiling the source; unless they're part of your current project, delete them.
   • Similarly, object files (*.o) can also be safely deleted.
   • Files named `core' were probably generated by a crashing program; unless you want to use a debugger to find what caused the crash, you should delete core files immediately. (Otherwise, delete after debugging.)
   • PostScript, DVI, and other formatted document files generated from *roff/TeX source files can be safely deleted.
2. Next, find out where your space is being used.
   • If you have a large directory structure, the command

         % du ~ | sort -n 
     

     will show you a list of all your directories in ascending order by the amount of space they use. (Use

         % du | sort -n
     

     to just look at the directory structure rooted at your current directory.)

   • The command

         % ls -als | sort -n
     

     will show you the files in your current directory, in ascending order by the amount of space they use.

   • Combining these two commands will help you discover where your usage is heaviest, and (therefore) where you should first look to trim your usage.

   • If your heaviest usage is in mail folders, you can use your mail-reading program (Pine, Elm, Mutt, for example) to view the folder contents; typically there will be some indication of the size of each message. In many cases, one or a few large messages can account for almost the entire size of the folder.

3. Finally, start freeing up your disk space.
   • The easiest thing to do with a bulky file (or set of files) is to delete it (or them).

     To delete a file, give the command

     % rm filename

     To delete an entire directory subtree, give the command:

     % rm -rf dirname

     This command should be used, of course, with extreme caution.

   • You can compress files that you aren't currently using but don't want to delete. For example:

         % gzip demo.c
     

     ... this will replace demo.c with a file named demo.c.gz typically taking up a lot less space. To get the original file back again:

         % gunzip demo.c.gz
     

     You can compress all the files in a directory (whose names don't begin with a period) with the command

         % gzip *
     

   • The best way to save space for a lot of inactive files is to create a "compressed tar archive". For example, to create a compressed tar archive of all files rooted at the current directory, give the commands:

         % tar cf demo.tar *
         % gzip demo.tar
     

     This will create the file demo.tar.gz. You can then safely delete all other files and directories in the current directory. To restore things, use the commands:

         % gunzip demo.tar.gz
         % tar xpf demo.tar
     

     (You can also extract single files from the archive if necessary. For more information on the tar and gzip programs, see the man pages.)

Last modified: 2005-08-05 10:06 EDT