How do I view a user's file permissions from the command line?
The Microsoft Windows NT Server 4.0 Resource Kit perms.exe
utility shows permissions on files and directories. Go to the command line and
type
perms <domain>\<user> <file>
Table 1 shows file and directory permissions.
Add /s to show details of subfiles and subdirectories. To output the
permissions to a file, add > filename.txt, using the name of the file
you want to direct the output to. The perms.exe utility has a bug that keeps it
from recognizing permissions given via a global group.
You can use NT's cacls.exe command to change a user's permissions from the
command line. To give a user named John read access to a directory called files,
go to the command line and type
cacls files /e /p john:r
The /e setting edits the access control list (ACL) instead of replacing it,
so other file and directory permissions do not change. The /p setting sets the
user's permissions. For more information about this command, go to the command
line and type
cacls /?
Can I delete files beginning with $ at the root of my NTFS drive?
You cannot delete files beginning with $ because you cannot remove the hidden flags. Moreover, you do not want to delete the files because they hold your NTFS volume information. Table 2 lists NTFS files. If you want to view the files, go to the command line and type
dir /ah $mft
What cluster size do FAT and NTFS partitions use?
Table 3 lists the default cluster size for FAT partitions. In Inside the
Windows NT File System, Microsoft does not recommend FAT volumes
larger than 511MB because the cluster increases to more than 16KB and wastes
space.
Table 4 lists the default cluster size for NTFS partitions. NTFS balances
the tradeoff of disk defragmentation from small clusters and wasted space from
large clusters.
When you format a drive, you can use the /a:size switch to change
the cluster size. Go to the command line and type
format d: /a:1024 /fs:ntfs
What can I do if Windows NT becomes unresponsive during an NTFS disk
operation (e.g., dir)?
When you perform a large NTFS disk operation such as dir/s *.* or ntbackup
:\*.*, NT might become unresponsive. NT updates NTFS files with a last access
stamp, and viewing thousands of files fills the NTFS log. NT locks up as it
waits to flush the NTFS log file to the hard disk.
You can prevent NTFS from updating the last access stamp. Start regedit.exe, and go to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem key. Select New, DWORD Value from the Edit menu, enter the
name NtfsDisableLastAccessUpdate, and click OK. Double-click the new value,
change the value to 1, and click OK. Close the Registry editor, and reboot.
What are alternate data streams?
You can use alternate data streams to hide data from Explorer and the dir command in NTFS files. You must know the file's stream name to view the data. A stream is an entry point into a file. You can create multiple streams to an NTFS file in the form filename:stream name.
Start a console window (cmd.exe). At the prompt, type
notepad normal.txt
Enter some text, and save the file on an NTFS partition. Edit the file
again, with a different stream (e.g., notepad normal.txt:hidden.txt). The system
then prompts you to create a new file. Enter some text, and save the file. When
you run the dir command, you see only the file normal.txt, with its original
size.
Each file can have multiple streams. When you copy a file, the streams
remain. Thus, if you copy the file normal.txt to the file john.txt, you get the
hidden stream (i.e., john.txt:hidden). You cannot use streams from the command
prompt because the command prompt does not recognize colons in filenames (except
in drive letters).
Microsoft does not provide a method to detect or delete hidden streams. To
detect streams, use March Information Systems' utility (http://streams.march.co.uk), or Frank Heyne's List Alternate Data Streams (LADS) command line tool
(http://rcswww.urz.tu-dresden.de/~fh/nt/ntfs-ads). To delete a stream,
copy the file to a FAT partition and then back to the NTFS partition. Type
- ren <file> temp.temp
- cat temp.temp > <file>
- del temp.temp
End of Article
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