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diff --git a/doc/quotas.ms b/doc/quotas.ms deleted file mode 100644 index 10e200c..0000000 --- a/doc/quotas.ms +++ /dev/null @@ -1,318 +0,0 @@ -.\" Copyright (c) 1983 The Regents of the University of California. -.\" All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 2. Redistributions in binary form must reproduce the above copyright -.\" notice, this list of conditions and the following disclaimer in the -.\" documentation and/or other materials provided with the distribution. -.\" 3. All advertising materials mentioning features or use of this software -.\" must display the following acknowledgement: -.\" This product includes software developed by the University of -.\" California, Berkeley and its contributors. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT -.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY -.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF -.\" SUCH DAMAGE. -.\" -.\" @(#)quotas.ms 6.3 (Berkeley) 4/17/91 -.\" -.EH 'SMM:4-%''Disc Quotas in a \s-2UNIX\s+2 Environment' -.OH 'Disc Quotas in a \s-2UNIX\s+2 Environment''SMM:4-%' -.ND 5th July, 1983 -.TL -Disc Quotas in a \s-2UNIX\s+2\s-3\u*\d\s0 Environment -.FS -* UNIX is a trademark of Bell Laboratories. -.FE -.AU -Robert Elz -.AI -Department of Computer Science -University of Melbourne, -Parkville, -Victoria, -Australia. -.AB -.PP -In most computing environments, disc space is not -infinite. -The disc quota system provides a mechanism -to control usage of disc space, on an -individual basis. -.PP -Quotas may be set for each individual user, on any, or -all filesystems. -.PP -The quota system will warn users when they -exceed their allotted limit, but allow some -extra space for current work. -Repeatedly remaining over quota at logout, -will cause a fatal over quota condition eventually. -.PP -The quota system is an optional part of -\s-2VMUNIX\s0 that may be included when the -system is configured. -.AE -.NH 1 -Users' view of disc quotas -.PP -To most users, disc quotas will either be of no concern, -or a fact of life that cannot be avoided. -The -\fIquota\fP\|(1) -command will provide information on any disc quotas -that may have been imposed upon a user. -.PP -There are two individual possible quotas that may be -imposed, usually if one is, both will be. -A limit can be set on the amount of space a user -can occupy, and there may be a limit on the number -of files (inodes) he can own. -.PP -.I Quota -provides information on the quotas that have -been set by the system administrators, in each -of these areas, and current usage. -.PP -There are four numbers for each limit, the current -usage, soft limit (quota), hard limit, and number -of remaining login warnings. -The soft limit is the number of 1K blocks (or files) -that the user is expected to remain below. -Each time the user's usage goes past this limit, -he will be warned. -The hard limit cannot be exceeded. -If a user's usage reaches this number, further -requests for space (or attempts to create a file) -will fail with an EDQUOT error, and the first time -this occurs, a message will be written to the user's -terminal. -Only one message will be output, until space occupied -is reduced below the limit, and reaches it again, -in order to avoid continual noise from those -programs that ignore write errors. -.PP -Whenever a user logs in with a usage greater than -his soft limit, he will be warned, and his login -warning count decremented. -When he logs in under quota, the counter is reset -to its maximum value (which is a system configuration -parameter, that is typically 3). -If the warning count should ever reach zero (caused -by three successive logins over quota), the -particular limit that has been exceeded will be treated -as if the hard limit has been reached, and no -more resources will be allocated to the user. -The \fBonly\fP way to reset this condition is -to reduce usage below quota, then log in again. -.NH 2 -Surviving when quota limit is reached -.PP -In most cases, the only way to recover from over -quota conditions, is to abort whatever activity was in progress -on the filesystem that has reached its limit, remove -sufficient files to bring the limit back below quota, -and retry the failed program. -.PP -However, if you are in the editor and a write fails -because of an over quota situation, that is not -a suitable course of action, as it is most likely -that initially attempting to write the file -will have truncated its previous contents, so should -the editor be aborted without correctly writing the -file not only will the recent changes be lost, but -possibly much, or even all, of the data -that previously existed. -.PP -There are several possible safe exits for a user -caught in this situation. -He may use the editor \fB!\fP shell escape command to -examine his file space, and remove surplus files. -Alternatively, using \fIcsh\fP, he may suspend the -editor, remove some files, then resume it. -A third possibility, is to write the file to -some other filesystem (perhaps to a file on /tmp) -where the user's quota has not been exceeded. -Then after rectifying the quota situation, -the file can be moved back to the filesystem -it belongs on. -.NH 1 -Administering the quota system -.PP -To set up and establish the disc quota system, -there are several steps necessary to be performed -by the system administrator. -.PP -First, the system must be configured to include -the disc quota sub-system. -This is done by including the line: -.DS -options QUOTA -.DE -in the system configuration file, then running -\fIconfig\fP\|(8) -followed by a system configuration\s-3\u*\d\s0. -.FS -* See also the document ``Building 4.2BSD UNIX Systems with Config''. -.FE -.PP -Second, a decision as to what filesystems need to have -quotas applied needs to be made. -Usually, only filesystems that house users' home directories, -or other user files, will need to be subjected to -the quota system, though it may also prove useful to -also include \fB/usr\fR. -If possible, \fB/tmp\fP should usually be free of quotas. -.PP -Having decided on which filesystems quotas need to be -set upon, the administrator should then allocate the -available space amongst the competing needs. How this -should be done is (way) beyond the scope of this document. -.PP -Then, the -\fIedquota\fP\|(8) -command can be used to actually set the limits desired upon -each user. Where a number of users are to be given the -same quotas (a common occurrence) the \fB\-p\fP switch -to edquota will allow this to be easily accomplished. -.PP -Once the quotas are set, ready to operate, the system -must be informed to enforce quotas on the desired filesystems. -This is accomplished with the -\fIquotaon\fP\|(8) -command. -.I Quotaon -will either enable quotas for a particular filesystem, or -with the \fB\-a\fP switch, will enable quotas for each -filesystem indicated in \fB/etc/fstab\fP as using quotas. -See -\fIfstab\fP\|(5) -for details. -Most sites using the quota system, will include the -line -.DS C -/etc/quotaon -a -.DE -in \fB/etc/rc.local\fP. -.PP -Should quotas need to be disabled, the -\fIquotaoff\fP(8) -command will do that, however, should the filesystem be -about to be dismounted, the -\fIumount\fP\|(8) -command will disable quotas immediately before the -filesystem is unmounted. -This is actually an effect of the -\fIumount\fP\|(2) -system call, and it guarantees that the quota system -will not be disabled if the umount would fail -because the filesystem is not idle. -.PP -Periodically (certainly after each reboot, and when quotas -are first enabled for a filesystem), the records retained -in the quota file should be checked for consistency with -the actual number of blocks and files allocated to -the user. -The -\fIquotacheck\fP\|(8) -command can be used to accomplish this. -It is not necessary to dismount the filesystem, or disable -the quota system to run this command, though on -active filesystems inaccurate results may occur. -This does no real harm in most cases, another run of -.I quotacheck -when the filesystem is idle will certainly correct any inaccuracy. -.PP -The super-user may use the -\fIquota\fP\|(1) -command to examine the usage and quotas of any user, and -the -\fIrepquota\fP\|(8) -command may be used to check the usages and limits for -all users on a filesystem. -.NH 1 -Some implementation detail. -.PP -Disc quota usage and information is stored in a file on the -filesystem that the quotas are to be applied to. -Conventionally, this file is \fBquotas\fR in the root of -the filesystem. -While this name is not known to the system in any way, -several of the user level utilities "know" it, and -choosing any other name would not be wise. -.PP -The data in the file comprises an array of structures, indexed -by uid, one structure for each user on the system (whether -the user has a quota on this filesystem or not). -If the uid space is sparse, then the file may have holes -in it, which would be lost by copying, so it is best to -avoid this. -.PP -The system is informed of the existence of the quota -file by the -\fIsetquota\fP\|(2) -system call. -It then reads the quota entries for each user currently -active, then for any files open owned by users who -are not currently active. -Each subsequent open of a file on the filesystem, will -be accompanied by a pairing with its quota information. -In most cases this information will be retained in core, -either because the user who owns the file is running some -process, because other files are open owned by the same -user, or because some file (perhaps this one) was recently -accessed. -In memory, the quota information is kept hashed by user-id -and filesystem, and retained in an LRU chain so recently -released data can be easily reclaimed. -Information about those users whose last process has -recently terminated is also retained in this way. -.PP -Each time a block is accessed or released, and each time an inode -is allocated or freed, the quota system gets told -about it, and in the case of allocations, gets the -opportunity to object. -.PP -Measurements have shown -that the quota code uses a very small percentage of the system -cpu time consumed in writing a new block to disc. -.NH 1 -Acknowledgments -.PP -The current disc quota system is loosely based upon a very -early scheme implemented at the University of New South -Wales, and Sydney University in the mid 70's. That system -implemented a single combined limit for both files and blocks -on all filesystems. -.PP -A later system was implemented at the University of Melbourne -by the author, but was not kept highly accurately, eg: -chown's (etc) did not affect quotas, nor did i/o to a file -other than one owned by the instigator. -.PP -The current system has been running (with only minor modifications) -since January 82 at Melbourne. -It is actually just a small part of a much broader resource -control scheme, which is capable of controlling almost -anything that is usually uncontrolled in unix. The rest -of this is, as yet, still in a state where it is far too -subject to change to be considered for distribution. -.PP -For the 4.2BSD release, much work has been done to clean -up and sanely incorporate the quota code by Sam Leffler and -Kirk McKusick at The University of California at Berkeley. |