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Full Discussion: How raw disks are read?
Top Forums UNIX for Advanced & Expert Users How raw disks are read? Post 302802765 by methyl on Saturday 4th of May 2013 06:13:54 PM
Old 05-04-2013
Point: With modern hardware a "raw disc" can be multiple physical discs which the Operating System sees as one physical disc.

Some research ideas:

Consider the case of a virgin disc. There are no filesystems unless your software creates a filesystem. You can write or read whatever you like within the physical dimensions of the disc.

The very basic filesystems follow the pattern of the original IBM tape format VOL1 HDR1.

For research purposes it is worth a look at CAFS (Content Addressable File Store). That's the way to use a raw disc! It's so much better than "Binary Tree", "Hash Random" or "Index Sequential" file systems when dealing with disorganised data.
 

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quotacheck(8)						      System Manager's Manual						     quotacheck(8)

Name
       quotacheck - file system quota consistency checker

Syntax
       /etc/quotacheck [ -v ] [ -f ] filesystem ...
       /etc/quotacheck [ -v ] -a

Description
       The  command examines each file system, builds a table of current disc usage, and compares this table against that stored in the disc quota
       file for the file system.  If detects any inconsistencies, it updates both the quota file and the current system copies	of  the  incorrect
       quotas.	Inconsistencies occur only if an active file system is checked.

       Normally,  returns a warning if it cannot find a valid quota file.  If you use the option, creates a quota file automatically and then per-
       forms its normal functions.

       If you use the flag in place of any file system name, checks all the file systems listed in to be read-write with disc quotas.

       Normally reports only modified quotas. If the option is supplied, will indicate the calculated disc quotas for each user  on  a	particular
       file system.

       The  command  expects each file system to be checked to have a quota file named in the root directory.  If none is present, will ignore the
       file system.

       The command is normally run at boot time from the file, before enabling disc quotas with For further information, see

       The command accesses the raw device in calculating the actual disc usage for each user.	Thus, the file systems checked should be quiescent
       while is running.

Files
       Default file systems

See Also
       quota(2), setquota(2), quotaon(8)
       ``Disk Quotas in a UNIX Environment,'' ULTRIX Supplementary Documents, Volume 3: System Manager

																     quotacheck(8)
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