Hints and Tips For SysOps Running Linux
By Janis Kracht 1:261/38 (janis@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              Display 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
ls -1                     -1 (one) shows file names in column list
                          with no other info
[janis@filegate]$ ls -1
[janis@filegate]$ _

File Management

DOS Linux Description
copy            cp               Copy a file
move            mv               Move a file
touch           touch            Set the time stamp 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

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
[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 file system for errors
n/a             swapon           Turn on a swap partition
n/a             swapoff          Turn off a swap partition
n/a             mount            Attach a file system to the
                                 root file system
n/a             umount           Detach a file system from the
                                 root file system
chkdsk          df               View amount of disk space
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
pkzip           zip             Create a zip file
pkunzip         unzip           Extract files from a zip file
n/a             gzip            Compress or decompress files via GNU
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 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 mylist="`ls -1 *.bad`"

for file in $mylist

        f=`basename $file .bad`.tic
        mv $file $f
============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`
test=`grep $file $tics`

     f=`basename $tics .tic`
     zip -jm0 $f.zic $file $tics
mv *.zic /home/bbs/binkd/barry
chown bbs.bbs /home/bbbs/binkd/barry/*
chmod /home/bbbs/binkd/barry/*
============end make_zic===================

Next, mvfile2in.sh 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`
if ps aux | grep ^$f

echo "===user $f online==="
elif test -e /home/$f/*/*.bsy

echo "$f bsy-flag exists"
echo "===safe to move files from $f===" mv /home/$f/in/* /home/bbbs/inbound
====end mvfile2in.sh==================

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

# import file_id.diz to files.bbs or descript.ion type file dir -1 *.zip > dirlist
for f in `cat dirlist`
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
=========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.

The following articles may be helpful - they contain some of the same information as above, but some additional information as well.