Getting Technical

For technical information about FidoNet please see www.ftsc.org

*LINUX OS*
By Janis Kracht
1:2320/38 (janisl@filegate.net)

Though many of us have converted our Operating Systems, bbs software, echomail tossers, and mailers to new ones many times, changing one's setup to run under Linux can be perhaps more challenging than anything else ever experienced <smile>.

Hopefully this article will be of some help if you have just switched to Linux, or if you are about to do so. I'll show you some comparisons between DOS and Linux so that you can see that Linux isn't as foreign as it might at first seem, and then I'll provide some scripts that I've written to perform various functions on my bbs system. Lastly, I'll also include a few notes regarding some things you should make sure do when you install linux. Security under Linux is a very large topic however, so I will cover that in more detail in a later article.

First off, let's look at some commands that you might commonly use under DOS, and their Linux counterparts. As you'll see, there are some commands that do not have an equivalent under DOS (i.e., I'm not counting DOS GNU utilities, etc. since these are not generally part of the standard DOS distribution.)

Tip: It would probably be a good idea to type 'man command', or 'info command', or 'command --help' without the quotes to see all the options of these Linux commands.

DOS         Linux  Description

command.com sh     Simplistic command interpreter
n/a         bash   Advanced command interpreter
n/a         perl   Interpreter for perl scripts
n/a         awk    Interpreter for awk scripts
n/a         chsh   Change shell

Directory Management

DOS         Linux   Description

dir         ls -l   Long format directory
dir         dir     Long format directory
dir /w      ls      Wide format directory
cd          cd      Change directory
rm          rmdir   Remove a directory
md          mkdir   Make a directory
deltree /Y  rm -rf  Recursively delete a directory
                      tree
n/a         pwd     Dispay the current working
                      directory path

Some Linux examples:

ls -d .*

Show only "." directories. (these are often configuration files, etc. for various programs). The -d indicates that only the directory name should be shown, not the contents.

ls -ltr

Sort by date, reverse order.

ls --color=auto

Turn on color for file types in directory list.

ls -1

-1 (one) shows file names in column list with no other info

[janis@filegate]$ ls -1
absHOWTO.zip
games.zip
Mail/
newfiles/
[janis@filegate]$ _

File Management

DOS         Linux  Description

copy        cp     Copy a file
move        mv     Move a file
touch       touch  Set the timestamp on a file
del         rm -f  Delete a file
type        cat    Print a file to the screen
n/a         chown  Change ownership of a file
n/a         chgrp  Change group ownership of a
file attrib chmod  Change access permissions of a
                   file
rawrite     dd     Write directly to a device
subst?      ln     Create a link to a file

Some Linux examples:

mv firstdoc.txt seconddoc.txt

rename firstdoc.txt

mv /janis/*.txt /afiles

move *.txt to directory afiles.

Tip: When moving groups of files with the same filename, such as mv *.tic *.bad, you must specify a different directory. To move files such as *.bad to *.tic, you can use the script in this article, mvbad2tic.

Aliases

You can tell the system to use aliases of the commands you use.

Enter these in your /etc/profile to make them global or ~/.bash_profile to make them local.

alias del='rm'
alias copy='cp'
alias move='mv'
alias ren='mv'
alias type='cat'
alias rd='rmdir'
alias md='mkdir'
alias help='man'

You can also enter them on the command line, just for that session. If you type: alias md='mkdir' you can then use md instead of mkdir.

Searching and Sorting

DOS    Linux    Description

find   grep     Search for a string in a text file
dir /s find     Search for a file
n/a    locate   Search for a file via a database
n/a    updatedb Create searchable database of files
sort   sort     Sort a file
n/a    tr       Translate, squeeze, and/or  delete
                   characters from standard input.

Some Linux examples:

Tip: ctime option in the find command will show status of a file that was last changed n*24 hours ago. daystart measure times (for -ctime, and other options for find) from the beginning of today rather than from 24 hours ago.

[bbs@filegate /home/bbs]$ find /home/ftp/pub -daystart -ctime 00
/home/ftp/pub/gamesnet/g_cons/descript.ion
/home/ftp/pub/gamesnet/g_cons/CC0CPC10.ZIP
/home/ftp/pub/gamesnet/g_cons/C19WKWK7.ZIP
/home/ftp/pub/gamesnet/g_cons/C50STR14.ZIP
/home/ftp/pub/gamesnet/g_cons/CABPRT20.ZIP
/home/ftp/pub/gamesnet/g_cons/CBCGRB02.ZIP
[bbs@filegate /home/bbs]$ _

Disk Management

DOS     Linux     Description

fdisk   fdisk     Modify the partition table
format  mke2fs    Create a filesystem on a partition
format  fdformat  Format a floppy disk
chkdsk  e2fsck    Test a filesystem for errors
n/a     swapon    Turn on a swap partition
n/a     swapoff   Turn off a swap partition
n/a     mount     Attach a filesystem to the root
                     filesystem
n/a     umount    Detach a filesystem from the root
                     filesystem
chkdsk  df        View amount of disk space available
dir/s   du        View amount of disk space used by a
                     directory recursively

Some examples of Linux commands: The mount command with no parameters specified shows you the devices currently mounted.

[bbs@filegate ~]$ mount
 /dev/hda1 on / type ext2 (rw) none on /proc
 type proc (rw) /dev/hdb1 on /export type ext2
    (rw) none on /dev/pts
 type devpts (rw,mode=0622)
[bbs@filegate ~]$_

Getting Help with Commands:

DOS   Linux       Description

help  man         Get help on a command
n/a   apropos     Get help on a general topic
n/a   whatis      Search the whatis database
n/a   makewhatis  Make the whatis database
n/a   file        Classify a file

Editing and Printing

DOS    Linux  Description

edit   pico   Editor for novices
n/a    vi     Editor for advanced users
print  lpr    Print a file
n/a    sed    Stream editor
n/a    joe    Wordstar compatible editor
n/a    emacs  Programming environment and editor
edlin  ed     non-visual editor

Backup, Compression, and Archival

DOS     Linux        Description

n/a     bzip2        A block-sorting file compressor, using
                     Burrows-Wheeler block sorting text
                     compression algorithm, and Huffman
                     coding
        bzcat        Decompresses files to stdout
        bunzip2      A block-sorting file compressor,
        bzip2recover recovers data from damaged bzip2 files
pkzip   zip          Create a zip file
pkunzip unzip        Extract files from a zip file
n/a     gzip         Compress or decompress files via GNU
                     zip.
n/a     tar          Tape archiver
n/a     compress     Lempel-Ziv compression program

Archivers: What's available:

Archivers which you may have used under DOS are available:

name:     date of last update for Linux:

zip       10/13/98
unzip     11/30/98
lha        6/28/99
unarj      6/22/99
pkzip251   4/15/99
arc        5/29/99
rar        6/21/00

Viewing multiple Archives:

As you probably know, under DOS unzip -v filename.zip will list the contents of one archive. To list the contents of multiple zip or rar archives, enclose the argument in quotes:

unzip -v "*.zip"

ex.: [bbs@filegate bbbs]$ unzip -v "*.zip"

Archive:  nodelist.zip
Length   Method  Size  Ratio  Date  Time CRC-32     Name
------  ------  ------- ----- ----  ---- -------    ------
1706292  Defl:N  560625 67% 09-14-99 15:57 a18214bc NODELIST.253
-------          -----  ---                         ------------
1706292          560625 67%                            1 file

Archive:  ppphowto.zip
Length   Method    Size  Ratio   Date   Time    CRC-32   Name
--------  ------  ------- -----   ----   ----   ------   ----
158718  Defl:N    48642  69%  10-16-99 20:32  b4ad98a9   PPP-HOWTO
--------          -----  ---                             -------
158718            48642  69%                             1 file

2 archives were successfully processed.

tar/gzip:

Tar and gzip are used commonly on Linux. Often you'll see archives with tgz extensions, .gz, or no extension at all. You can use the file command to see how the file is archived/stored if there is no extension or if you are just curious:

[bbs@filegate bbbs]$ file ZPMF025D.TGZ ZPMF025D.TGZ: gzip compressed data, deflated, last modified: Thu Jun 8 04:55:16 1995, max compression, os: Unix

So you'd need to un-gzip this file first, then un-tar it.

gzip -d ZPMF025D.TGZ

This results in the file ZPMF025.tar

To list the contents of the tar file, type tar tf filename.tar To extract the tar, type tar xf filename.tar

There are options to "keep old files" with both gzip and tar which you may also want to include on the command line. The default action is to remove the original tar. See tar --help, and gzip --h for more info.

This shortcut extract both the tar and gzip files in one command:

tar xvzf filename.tar.gz

The "z" flag says "un-gzip before un-tarring". The same flag works in reverse when tarring.

Some BASH Scripts

One of the neatest things about *nix systems is that any file can be made executible by simply changing the attributes of the file. Of course, if the text file doesn't have any useful commands in it, it won't "do" anything <smile>.

Here are some scripts I've written for my bbs - none of these contain any startling ideas, and I don't doubt a number of them could be done better, but you can feel free to modify them as you like or need. info bash will show you the system's man pages for these scripting keywords. To use these scripts, save them to a file and then make them executible with 'chmod a+x filename' without the quotes. To call them you can type 'sh filename' without the quotes, where filename is the name of the script. Again, scripting is a very broad subject ... looks like I will be writing yet another article concerning that subject later :)

====mvbad2tic====
#!/bin/sh
# the above must be the first line in the script.
# the # symbol specifies a comment line
list="`ls -1 *.bad`"
for file in $list
 do
  f=`basename $file .bad`.tic
  mv $file $f
done
====end mvbad2tic

====make_zic====
#!/bin/sh
# make_zik takes a file and it's accompanying
# tic and puts them both in one zip archive aka
# Allfix's zic option
dir -1 -I*.tic -I*.sh -Iticlist-Iarchives >> archives
dir -1 *.tic >> /home/bbbs/binkd/work/ticlist
for file in `cat archives`
do
for tics in `cat ticlist`
 do
  if test=`grep $file $tics`
   then
   f=`basename $tics .tic`
   zip -jm0 $f.zic $file $tics
  fi
 done
done
mv *.zic /home/bbs/binkd/barry
chown bbs.bbs /home/bbbs/binkd/barry/*
chmod 775 /home/bbbs/binkd/barry/*
====end make_zic====

Next, mvfile2in.sh move files from a users inbound. It uses another file you must create named dirlist. dirlist contains the names of your users' home directories which will most likely be the same as the username.

You can create this file with the command: dir /home/* -1 > dirlist Edit it to remove other entries you don't want, like ftp, etc. which may be in the /home directory.

====mvfile2in.sh====
#!/bin/sh
cd /home/bbbs
# move files from a users' inbound to the bbs' inbound
# tests to see if user is online before moving anything.
cd /home/bbbs
for f in `cat /home/bbbs/dirlist`
 do
if ps aux | grep ^$f
   then
   echo "===user $f online==="
elif test -e /home/$f/*/*.bsy
then
     echo "$f bsy-flag exists"
else
 echo "===safe to move files from $f==="
 mv /home/$f/in/* /home/bbbs/inbound
fi
done
====end mvfile2in.sh====

get_desc can be used to import file descriptions to a files.bbs or descript.ion type file list.

====get_desc====
#!/bin/sh
# import file_id.diz to files.bbs or descript.ion type file
dir -1 *.zip > dirlist
for f in `cat dirlist`
do
  unzip -pC $f file_id.diz >> FILE_ID.DIZ
  if [ -f FILE_ID.DIZ ] ;
# this script uses an abbreviation for the the test command, [ and ].
# I believe Pertti Heikkinen posted this in the bbbs.english echo.
then
     tr '\n\r' ' ' <FILE_ID.DIZ >tmp.ff
     echo $f `cat tmp.ff` >> descript.txt
     rm -f FILE_ID.DIZ tmp.ff
  fi
done
====end get_desc====

Some Install Concerns for the SysOp Installing Linux

The first concern is pretty simple. When you log into your system it will be very tempting to login as root, or the superuser, because user root has no limitations, can run any program, read/write any file.. and ...also can delete every single file on your system <g>. Issuing a command like rm -r from the / directory as user root will surely go through the entire directory tree and do just what you told it to do (rm -r deletes recursively... <ouch>. )

Of course there will be times when you must log on as root to do things such as install your apache web server, configure your ppp connection, etc., but that is really the only time you should log in as root. Likewise, you should never log in as root in XWindows as user root, except as above. XWindows can destroy your data if you are user root and are playing with commands.

Big Tip: Use the adduser command to create other users on your system which you can use on a daily basis. To add a user, as root, type:

adduser username

where username is the name you have selected, 8 characters or less. Linux will let you use longer names for the users, but will truncate them. The adduser command adds the user to the passwd file in /etc/passwd, and unless you specify otherwise, creates a directory off /home which is that user's 'home' directory. These limited-access users can only harm the files they own in their home directory. Next you assign that user a password with the passwd command by typing:

passwd username

The passwd command prompts you for this users' password, 8 characters or less since again it will be truncated if it's over 8 characters. The password you choose should be a combination of upper and lower case alpha characters and numbers.

Tip: Try to make the password something that means something to you, then use the letters of the words to make up your password. Here's an example of what I mean ...

I love Chocolate cake I'll take two thanks = IlccIt2t

The last section of this article is pretty important. With the number of systems online 24/7, these issues cannot be ignored. If you think your system is safe from those who would test and probe your system for ways of gaining illegal entry, think again.

Tip: After installing linux, the very first thing you should do is pull up your favorite text editor, and edit the inetd.conf file which lives in /etc (/etc/inetd.conf). Comment out every single line in that file except for the one that refers to ftp if you figure to use ftp. If you think this sounds drastic, well, it is. And it's necessary. If you leave the file as is, you are leaving an incredible number of ports and services open to trouble-makers who will (most likely) be port-scanning your system over and over again looking for weak points. You probably won't need any of the services you are commenting out - and some of them, like rlogin, are incredibly famous for having holes where hackers can gain access to your system.

Tip: Use ssh, (Secure Shell) instead of telnet. Comment telnet out from inetd.conf. If you think are going to need telnet so that you can telnet into your system remotely, DON'T. Use Secure Shell instead. If Secure Shell isn't already on your system, go to http://rpmfind.net and download and install it.

Tip: If your distribution of linux installs wu-ftpd, install a different ftp daemon, such as Bero-ftpd, or Proftpd. Why the switch? Well, Wu-ftpd has been known over the years to have holes where creeps can gain illegal access to your system. Technically speaking these holes are plugged with new releases, but ... in general it is a good idea to install one of the other daemon's mentioned.

Tip: All of the above is good, but don't rest easy yet.. Another thing you must do is contantly stay aware of upgrades to the software you use. If, for example, a new version of bero-ftpd is released, install it. Upgrades under linux are not always done to make the software prettier or sexy <g>. The site that maintains the software you use will always post what type of upgrade the software is and whether it is a security upgrade.