Date:Sat Mar 30 14:23:24 (PST)
From:Phil Hughes
Many businesses place a firewall between the Internet and the inside systems. This is good protection and it just makes good sense. One common firewalling technique is to serverly restrict access through the firewall from the outside but allow a user on the inside to do most anything through the firewall to the outside.
When I am at home, I routinely need to move files between home and work. But, because of the firewall, I can ftp from work to home but not the other way around. What this means is that I need to establish an interactive connection (using ssh) from home to work and then initiate the ftp from work to home.
So far, so good. But, what I call "home" consists of various locations, all connected with a dial-up connection through one of four ISPs. All four ISPs use dynamic IP addresses meaning that each time I connect I have a different IP address for my home system. Even though the ISP knows what the current IP address for my system, the name server at work doesn't.
The solution is to enter the IP address of my home system into the ftp command at work. First, I need to find out what the IP address is. To do that, I execute the ifconfig command on my home system:
$ /sbin/ifconfig lo Link encap:Local Loopback inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0 UP BROADCAST LOOPBACK RUNNING MTU:2000 Metric:1 RX packets:19 errors:0 dropped:0 overruns:0 TX packets:19 errors:0 dropped:0 overruns:0 eth0 Link encap:10Mbps Ethernet HWaddr 02:60:8C:8F:A2:08 inet addr:198.186.207.131 Bcast:198.186.207.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:969719 errors:0 dropped:0 overruns:0 TX packets:971132 errors:0 dropped:0 overruns:0 Interrupt:9 Base address:0x280 Memory:d8000-da000 ppp0 Link encap:Point-Point Protocol inet addr:206.125.79.118 P-t-P:204.157.220.30 Mask:255.255.255.0 UP POINTOPOINT RUNNING MTU:296 Metric:1 RX packets:5434 errors:0 dropped:0 overruns:0 TX packets:5545 errors:0 dropped:0 overruns:0 $The inet addr for the ppp0 interface (206.125.79.118) is the number I need. Now, on my system at work I enter:
$ ftp 206.125.79.118ftp then prompts for a login and password. I enter my standard login and password for my home system and ftp is up and running.
Date: Sun Mar 23 23:20:51 1997 (PST)
From: Kevin Lyda
In the march gazette raul miller suggested that the most portable way to test if you're root is [ -w / ]. that won't work if you're root file system is read only. [ -w /var ] might be a better method.
kevin
Date:Wed Mar 5 16:32:49 1997(PST)
From:Michael Hammel,
I wasn't aware of Xli (rather, I haven't looked at it), however your statement that xv can only tile image on the background. xv allows qutie a bit of command line control. I use the following to put up a background image at work (non-tiled, takes up the whole background):
xv -root -max -quit /export/home/mjhammel/lib/images/emass3.tga
The initial image is 601x339, with a root display of 1152x900. Since the original image is 24bpp the enlargement is very accurate in details.
Michael J. Hammel
Date:Thu Mar 20 12:22;34 1997(PST)
From:Paul Sephton
I have been enjoying the fruits of the Linux Gazette for a number of years now. Recently, I had one of my users accidentally type rm *>bak, and immediately noticed something was amiss by the incoherent screams eminating from her office.
In an attempt to ensure this would not have the same disasterous effect again, and to protect my eardrums in future, I spent a couple of days excersising my bash shell scripting skills, and came up with what I believe to be a decent mechanism for maintaining versioned backups.
My attitude with regard to the normal cludges like aliasing rm and so on, is that it will not protect you against other programs which unlink files. (To date I have yet to write a C program that shells rm in order to unlink a file :)
Whilst writing the set of three scripts, it dawned on me that although some more complex tools do exist which perform the same sort of function, the Linux community might be interested in what I did.
Although it's not much more than a creative excersise in the use of the 'find' command, and suffers from the usual limitation of being restricted to the one file system, I include the three scripts for your perusal and possible inclusion in the gazette at your discretion.
Don't hesitate to contact me if you need more information.
Kind regards, and many thanks for the gazette.
Paul Sephton
#!/bin/sh if [ -z "$SAFEDEL" ];then SAFEDEL=/u/safedel fi NDAYS=5 #Erase files after 2 days MAXVER=6 # Start Overwriting versins at this count BINDIR=$SAFEDEL/bin # Binaries directory DATADIR=$SAFEDEL/data # Where links are to go LOGFILE=$BINDIR/safedel.log # Output messages go here ERRLOG=$BINDIR/safedel.err # Error output messages go here DIRLIST=$BINDIR/safedel.dirs # List of directories found here LOCKFILE=$BINDIR/safedel.lock # Lockfile to prevent re-entry # Process the file $1 by creating a symbolic link in the data directory # and an entry for the file in the index. process-file() { SRC=`dirname $1` FNAME=`basename $1` VERSION=0 if [ ! -d $DATADIR$SRC ]; then mkdir -p $DATADIR$SRC # OWNER=`find -name $SRC -printf "%u"` # chown $OWNER $FNAME:$VERSION fi cd $DATADIR$SRC while [ -f $FNAME:$VERSION ]; do VERSION=$[ $VERSION + 1 ] done if ! ln $1 $FNAME:$VERSION 2>> $LOGFILE; then echo "Could not link file $FNAME:$VERSION" >> $LOGFILE return fi echo -e "Linked $FNAME:$VERSION \t \tin $SRC" >> $LOGFILE return } # Erase a file erase-file() { echo "Unlinking $1 $2" >> $LOGFILE rm -f $1 FN=`echo $1 | cut -f 1 -d ':'` if ! { echo "$ERASED" | grep "$FN" - } ; then ERASED="$ERASED $FN" fi return } # We want the version numbers to follow on each other, so that the next # file we create gets a bigger version number. This makes sure they follow. reorganise() { if [ -z $1 ]; then return fi FN=$1 FILE_LIST=`ls $FN:* | sort -n -t: -k2` if [ "$FILE_LIST" = ":*" ]; then echo "All [$FN:*] files erased" >> $LOGFILE return fi echo -e "File list to be moved is:\n$FILE_LIST" >>$LOGFILE VERSION=0 for FNAME in $FILE_LIST; do if [ "$FNAME" != "$FN:$VERSION" ]; then echo "Moving $FNAME $FN:$VERSION" >>$LOGFILE mv $FNAME "$FN:$VERSION" VERSION=$[ $VERSION + 1 ] fi done } # The main shell script starts here... cd $BINDIR if [ -f $LOCKFILE ]; then exit 0 fi touch $LOCKFILE date >> $LOGFILE cat $DIRLIST | ( while read SRC ; do if [ `echo $SRC | cut -b 1` != "#" ]; then echo "Finding files in $SRC" >> $LOGFILE echo "Point 1 ($SRC)" for FNAME in `find $SRC -type f -xdev -links 1 -print`; do process-file $FNAME done fi done ERASED="" echo "Point 2" for FNAME in `find $DATADIR -type f -links 1 -ctime $NDAYS -print`; do erase-file $FNAME "(older than $NDAYS days)" done echo "Point 3" for FNAME in `find $DATADIR -type f -name "*:$MAXVER" -print`; do FN=`echo $FNAME | cut -f 1 -d ':'` erase-file $FN:0 "Too many versions (VERSION > $MAXVER)" done echo "Point 4" for FNAME in "$ERASED"; do reorganise $FNAME done ) 2> $ERRLOG > /dev/null rm -f $LOCKFILE
#!/bin/sh CURRDIR=`pwd`/ if [ -z $SAFEDEL ]; then SAFEDEL=/u/safedel fi DATADIR=$SAFEDEL/data BINDIR=$SAFEDEL/bin cd $DATADIR$CURRDIR if [ -z "$1" ]; then echo echo "Restores files unintentionally deleted" echo echo "Useage <salvage <filename>[:version] [dest]> from within the directory" echo " in which the file was deleted." echo echo "The following is a list of your backed up files and their versions:" echo " Salvageable Files:" find . -xdev -type f -maxdepth 1 -links 1 -printf "%P\n" | column echo " Files Currently in Use:" find . -xdev -type f -maxdepth 1 -not -links 1 -printf "%P\n" | column else FN=`echo "$1:end" | cut -f 1 -d ':'` VER=`echo "$1:end" | cut -f 2 -d ':'` EXIST=`find $CURRDIR -name "$FN"` # echo "[$EXIST]" if [ -n "$EXIST" ]; then echo "Incorrect file specification: File(s) are not deleted. ($FN)" exit 0 fi if [ "$VER" = "end" -o "$VER" = "*" ]; then VER="" fi FILE_LIST=`find . -name "$FN:*" -printf "%f "` FLIST="" # echo "FILE_LIST is $FILE_LIST" for FNAME in $FILE_LIST; do FN=`echo "$FNAME:end" | cut -f 1 -d ':'` FOUND=0 # echo "Looking for [$FN] in [$FLIST]" for F in $FLIST; do if [ "$F" = "$FN" ]; then FOUND=1 fi done if [ "$FOUND" = "0" ]; then FLIST="$FLIST $FN" fi done # echo "FLIST is $FLIST" for FNAME in $FLIST; do if [ -z "$VER" ]; then VERSION=0 NEXTVER=1 while [ -f $FNAME:$NEXTVER ]; do VERSION=$NEXTVER NEXTVER=$[ $NEXTVER + 1 ] done else VERSION=$VER fi if [ ! -f $FNAME:$VERSION ]; then echo "File $FNAME:$VERSION not found" exit 0 fi if [ -z "$2" ]; then DEST=$CURRDIR$FNAME else DEST=$CURRDIR$2 fi if ln $FNAME:$VERSION $DEST 2> /dev/null; then echo "File $FNAME:$VERSION successfully recovered" else echo "Cannot link $FNAME:$VERSION to $DEST" fi done fi
#!/bin/sh if [ -z $SAFEDEL ]; then SAFEDEL=/u/safedel fi BINDIR=$SAFEDEL/bin # Binaries directory DATADIR=$SAFEDEL/data # Where links are to go # Erase a file reorganise() { if [ -z $1 ]; then return fi FN=`echo "$1:end" | cut -f 1 -d ':'` FILE_LIST=`ls $FN:* | sort -n -t: -k2` if [ "$FILE_LIST" = ":*" ]; then echo "All [$FN:*] files erased" return fi # echo -e "File list to be moved is:\n$FILE_LIST" VERSION=0 for FNAME in $FILE_LIST; do if [ "$FNAME" != "$FN:$VERSION" ]; then echo "Moving $FNAME $FN:$VERSION" mv $FNAME "$FN:$VERSION" VERSION=$[ $VERSION + 1 ] fi done } # The main shell script starts here... CURRDIR=`pwd`/ echo "Safedel: Purging extra versions in $CURRDIR" cd $BINDIR find $DATADIR$CURRDIR -type f -maxdepth 1 -links 1 -exec rm {} \; for FNAME in `find $DATADIR$CURRDIR -type f -maxdepth 1 -print`; do reorganise $FNAME done