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This document helps answer the question "why can't I edit
file 'foo' on the web server?" It includes links to web tools that allow you to
examine the file attributes of files on the web server, and to see what groups you
belong to- information that will help you answer that question.
Where Are the Goods?
Web server files are available in the /cse/www/ file tree. That tree
is mounted on all the "research" Unix hosts, and is accessible to Windows users
via either Samba or NTDFS. For example, you can map \\ntdfs\cs as a drive
and navigate down to \cse\www using Windows Explorer. The web server
runs a Unix-like operating system, and web server files are on a Unix file system.
Who Can Edit the Files?
Unix file permissions are defined in terms of three classes of users and three distinct
permissions. The user classes are:
- Owner. Every file is owned by a single user.
- Group. Every file is associated with a single Unix group. A group is simply a list
of users, such as offic_cs, that share a need to collaborate.
- World. Every other user is in this class.
The permissions are these:
- Read. The file can be opened and the contents examined.
- Write. The contents of the file can be changed.
- Execute. The file can be run as a program.
To be able to edit a file, it needs to be writable by you. That means either
- You own the file, and it is writable by owner, or
- You are a member of the group associated with the file, and it is writable
by group, or
- It is writable by world.
How Can I Tell if I Can Edit a File?
- To see what the permission settings are for a particular file, follow
this link.
Unix users can use ls to see permission settings. For example,
ls -l /cse/www/index.html.
- To see what groups you belong to, follow
this link.
Unix users can use the groups command.
It's Not Group-writable- What Now?
If you are a member of the group that is associated with a file, but
group-write is not set, all is not lost. Follow this sequence of operations
(Windows users can use the Windows Explorer to do each step):
- Copy the file to a new filename. For example, a Unix user could type:
cp /cse/www/directory/file.html /cse/www/directory/newfile.html
- Delete the orginal file. On Unix:
rm /cse/www/directory/file.html.
- Rename the copy to the original name. On Unix:
mv /cse/www/directory/newfile.html /cse/www/directory/file.html.
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