rsalz@uunet.uu.net (Rich Salz) (05/10/88)
Submitted-by: Dave Settle <oscar.smb.co.uk!dave>
Posting-number: Volume 14, Issue 88
Archive-name: diskhog
[ Be very careful before installing this... --r$ ]
I'm submitting a System V disk quota system, which encourages
users to keep their disk usage within a given limit. If they fail to do
this, they get a restricted login shell, which only allows them to
remove/backup files.
Basically it consists of a check script, run once per night, and a
restricted shell invoked if a user exceeds their disk quota for too long.
The whole system is called 'diskhog'.
P.S.: I'm leaving my job here... My mail address will continue to operate
for the next couple of months.
------------------------------ CUT HERE -----------------------------------
#! /bin/sh
# This is a shell archive, meaning:
# 1. Remove everything above the #! /bin/sh line.
# 2. Save the resulting text in a file.
# 3. Execute the file with /bin/sh (not csh) to create:
# README
# Makefile
# configure
# dcheck
# diskhog
# nohog.c
# csh_hog.c
# diskhog.h
# allowed
# dcheck.1
# diskhog.1
# nohog.1
# alternate
# README.nr
export PATH; PATH=/bin:/usr/bin:$PATH
echo shar: "extracting 'README'" '(6529 characters)'
if test -f 'README'
then
echo shar: "will not over-write existing file 'README'"
else
cat << \SHAR_EOF > 'README'
Page 1 February 10, 1988
1. Disk Quotas for System V.
I've found this very useful on my system, where it
encourages people to keep their disk usage down, without all
the hassle of having to complain to them personally. The
package runs a check each night on each user, and sends mail
to those anti-social people exceeding their allowance.
If, after a suitable number of warnings, these people
do not remove their extra files, their next login receives a
restricted shell, where the only available commands are
those for removing and backing up files.
You can decide on the range of commands available, and
place these in the directories "/diskhog" and
"/usr/diskhog", so the restricted shell can be as nasty as
you like. (You could be really vicious and just have "rm",
but it's probably advisable to have some commands to save to
tape and/or floppies). Make sure that any shell scripts set
PATH appropriately, if they use commands outside "/diskhog"
and "/usr/diskhog".
It counts up (using 'du') all the blocks used in the
user's sub-tree, and then compares this against the
allowable maximum for that user. Users with no specified
maximum are assumed to have unlimited disk allocations. All
the files, irrespective of owner, are counted in the user's
subtree, which is perhaps a little unfair ...
2. How it works.
Basically, there is a file called "allowed", which has
a list of the number of disk blocks (as per "du") which each
user is allowed. The format of this file is
<user> <allowance>
where <user> is the user's login name, and <allowance> is
the maximum number of block they are allowed (as per "du").
Each night, the script "dcheck" is run from the root
crontab entry, and checks each user's allowance. If the user
has more than the allowance, a mail message is sent to the
user asking them to remove some files.
If after a certain number of days the user has not
removed enough files, then a diskhog "tag" is created. The
next time the user logs on, the shell notices this tag, and
spawns a restricted shell via the script "diskhog".
Page 2 February 10, 1988
When running via "diskhog", the user's PATH is set to
"/diskhog:/usr/diskhog", so that you can restrict the
commands which are available. On my system, all the commands
in these directories relate to removing files, and
formatting floppy disks to put them on.
When the user logs out of the restricted shell, another
disk check is performed, and if enough blocks have been
removed, the login is allowed to proceed. If not, "diskhog"
is run again. "Diskhog" is interrupt-proof, but can be
killed by a SIGHUP signal (i.e. turning off the terminal).
In order to prevent the user from removing the diskhog
"tag" file, the tag file is placed in a directory owned by
root, which is not writeable by anyone else. The tag file is
removed by a special command "nohog", which is executed by
"diskhog" when enough files have been removed. "Nohog" runs
suid root, and is (hopefully) immune from fraud: it always
removes the tag of the login user.
Obviously, you should not put "nohog" in the restricted
PATH, or the user would be able to remove their own diskhog
tag!
All you need to run disk quotas is:
1. An "allowed" file, containing disk allowances.
2. If your system has "csh", then you need to type "make
csh", since csh does not have a system-wide init file.
A small program is provided, which makes the relevant
check, and then calls the real csh.
3. Add a line to the beginning of the file "/etc/profile"
which reads:
if [ -f DQUOTAS/hogs/$LOGNAME ] ; then diskhog ; fi
where DQUTOAS is replaced by your disk quota admin
directory (see Makefile).
4. Make yourself an entry in the root crontab, which runs
the program "dcheck" sometime during the night.
This will read something like:
03 01 * * * /usr/bin/dcheck
to run at 01:30 am every night.
Page 3 February 10, 1988
5. Check the definitions at the start of the script
'dcheck', and make sure they reflect your system.
3. Using csh with diskhog
Since my "csh" doesn't have a system-wide
initialisation file, it's difficult to intercept the logins
of people using the c-shell.
I decided to intercept /bin/csh itself, so I moved the
real csh to /etc/csh, and wrote a stub program which just
checks for a tag file, and calls diskhog if it finds it.
Then it calls the real csh.
This works fine on my system, but make sure it's not
going to interfere with things on your system before you
install it.
4. Watch out
Watch out for people who move their stuff to another
directory! 'dcheck' only checks things in the $HOME subtree.
Make sure that you put a correct PATH specification in
any shell scripts in '/diskhog' and '/usr/diskhog',
otherwise they won't work!
Have fun.
Dave Settle, SMB Business Software, Thorn EMI Datasolve
UUCP:
dave@smb.co.uk
...!mcvax!ukc!nott-cs!smb!dave
SMAIL: Voice:
SMB Business Software +44 623 651651
High Street
Mansfield Telex:
Nottingham NG18 1ES 37392 TECSMG
England
Fax:
+44 623 659947
SHAR_EOF
if test 6529 -ne "`wc -c < 'README'`"
then
echo shar: "error transmitting 'README'" '(should have been 6529 characters)'
fi
fi
echo shar: "extracting 'Makefile'" '(798 characters)'
if test -f 'Makefile'
then
echo shar: "will not over-write existing file 'Makefile'"
else
cat << \SHAR_EOF > 'Makefile'
#
BIN=/usr/bin # directory for binaries
DQUOTAS=/usr/lib/disk # directory containing all the info
#
SRC=README Makefile configure dcheck diskhog nohog.c csh_hog.c \
diskhog.h allowed dcheck.1 diskhog.1 nohog.1 alternate README.nr
config: .config
.config:
sh configure
@touch .config
install: nohog dcheck diskhog allowed ${DQUOTAS}/hogs
@echo "If your system has csh, maybe you need to 'make csh'"
@echo "Try 'make -n csh' first."
chown root nohog
chmod 4111 nohog
cp nohog ${BIN}
chmod +x dcheck diskhog
cp dcheck diskhog ${BIN}
cp allowed ${DQUOTAS}
csh: csh_hog
if [ ! -f /etc/csh ] ; then mv /bin/csh /etc/csh ; fi
cp csh_hog /bin/csh
${DQUOTAS}/hogs:
mkdir ${DQUOTAS}/hogs
shar: ${SRC}
shar -cv ${SRC} > diskhog.shar
README: README.nr
nroff -cm README.nr > README
SHAR_EOF
if test 798 -ne "`wc -c < 'Makefile'`"
then
echo shar: "error transmitting 'Makefile'" '(should have been 798 characters)'
fi
fi
echo shar: "extracting 'configure'" '(1606 characters)'
if test -f 'configure'
then
echo shar: "will not over-write existing file 'configure'"
else
cat << \SHAR_EOF > 'configure'
#
# shell script to install diskhog
#
DQUOTAS="/usr/lib/disk"
BIN="/usr/bin"
echo "Hi there, just a few questions about your system ..."
cat << EOF
I need a place to hold all the information about disk usage and allowances.
I would suggest using the directory $DQUOTAS.
EOF
echo "If you want a different one, enter it here: \c"
read ANS
if [ "$ANS" != "" ]
then
DQUOTAS=$ANS
echo "OK, using $DQUOTAS"
fi
if [ -f $DQUOTAS ]
then
echo "Oh dear, that seems to be a file"
echo "That won't do at all ..."
exit 0
else
if [ -d $DQUOTAS ]
then
echo "That directory already exists - I hope it's empty\n"
else
echo "Making a new directory"
mkdir $DQUOTAS $DQUOTAS/hogs
chmod 755 $DQUOTAS/hogs
chown root $DQUOTAS/hogs
fi
fi
cat << EOF
Where do you intend to install the programs?
I would suggest $BIN, but you might use another directory.
EOF
echo "If you want a different directory, enter it here: \c"
read ANS
if [ "$ANS" != "" ]
then
BIN=$ANS
echo "OK - using $BIN"
fi
echo "OK - reconfiguring the system ... \c"
cat << EOF > diskhog.h
#define DQUOTAS "$DQUOTAS"
#define BIN "$BIN"
EOF
ed dcheck << EOF > /dev/null
/^DQUOTAS=/c
DQUOTAS=$DQUOTAS # directory containing all the info
--
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