Unix Tip: KEEP THE USERS OFF WITH NOLOGIN

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3528 - October 7, 2010

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KEEP THE USERS OFF WITH NOLOGIN

There is a way to disable any new login attempts into a
system. This can be achieved by simply creating a file
called /etc/nologin.

It can have a null file size or a message can be
placed into the file informing the status of the
system. If a user attempts to login remotely, a
message will display with contents of the
/etc/nologin file, and then disconnect the user.

However, ftp connections are not affected by this, if
ftpd is running.

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DISCLAIMER: All UNIX HOT TIPS ARE OWNED BY THE UNIX GURU UNIVERSE AND ARE
NOT TO BE SOLD, PRINTED OR USED WITHOUT THE WRITTEN CONSENT OF THE UNIX
GURU UNIVERSE. ALL TIPS ARE "USE AT YOUR OWN RISK". UGU ADVISES THAT
ALL TIPS BE TESTED IN A NON-PRODUCTION DEVELOPMENT ENVIRONMENT FIRST.

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Unix Tip: KILL A USER, IN THE UNIX SENSE

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3527 - October 6, 2010

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KILL A USER, IN THE UNIX SENSE

DISCLAIMER: UGU is not telling you to kill your users.
If you so choose to it is at your own discretion and you
are doing it at your own risk.

Although we all have that ONE USER...

To kill all the processes associated with a particular user
simply:

# kill -9 `ps -aef|grep jondoe |awk '{ print $2 }'`

If you want to be a nice admin, tell him first.

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DISCLAIMER: All UNIX HOT TIPS ARE OWNED BY THE UNIX GURU UNIVERSE AND ARE
NOT TO BE SOLD, PRINTED OR USED WITHOUT THE WRITTEN CONSENT OF THE UNIX
GURU UNIVERSE. ALL TIPS ARE "USE AT YOUR OWN RISK". UGU ADVISES THAT
ALL TIPS BE TESTED IN A NON-PRODUCTION DEVELOPMENT ENVIRONMENT FIRST.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Unix Tip: JUST THE DIRECTORIES

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3526 - October 5, 2010

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JUST THE DIRECTORIES

It useful to be able to list all directories in
the current directory without any of the files.

ls -l | grep "^d"

Alias it by adding this in your .login
or .profile or .cshrc files in your home directory:

alias dir 'ls -l | grep "^d"'

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==========================================================================
DISCLAIMER: All UNIX HOT TIPS ARE OWNED BY THE UNIX GURU UNIVERSE AND ARE
NOT TO BE SOLD, PRINTED OR USED WITHOUT THE WRITTEN CONSENT OF THE UNIX
GURU UNIVERSE. ALL TIPS ARE "USE AT YOUR OWN RISK". UGU ADVISES THAT
ALL TIPS BE TESTED IN A NON-PRODUCTION DEVELOPMENT ENVIRONMENT FIRST.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
==========================================================================

Unix Tip: LOCK THAT FILE DOWN

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3525 - October 4, 2010

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LOCK THAT FILE DOWN

Sometimes you want to make a file very very secure.

To do this, change the permissions to 000

# chmod 000 [file]

No one except root will be able to access it.
Even the owner will have to change the
permissions to be able to do anything to it.

Although It's like a red flag that says..
"I'm an important file"

NOTE: DO NOT EVER DO THIS TO THE /etc/passwd FILE!

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==========================================================================
DISCLAIMER: All UNIX HOT TIPS ARE OWNED BY THE UNIX GURU UNIVERSE AND ARE
NOT TO BE SOLD, PRINTED OR USED WITHOUT THE WRITTEN CONSENT OF THE UNIX
GURU UNIVERSE. ALL TIPS ARE "USE AT YOUR OWN RISK". UGU ADVISES THAT
ALL TIPS BE TESTED IN A NON-PRODUCTION DEVELOPMENT ENVIRONMENT FIRST.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
==========================================================================

Unix Tip: UMOUNT BUSY DEVICES

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3524 - October 3, 2010

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UMOUNT BUSY DEVICES

The "umount" command unmounts a currently
mounted filesystem, which can be specified either
as a mounted-on directory or a filesystem.

If a mount point is busy, there are a couple
things to try:

On some non-BSD based machines you can use the
command "umount -k" to force the system to drop a
busy device.

# umount -k /hosts/foo

If you are on a standalone system or none of the
filesystems are being exported, then "cd /" in
all open shells or windows and umount.

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==========================================================================
DISCLAIMER: All UNIX HOT TIPS ARE OWNED BY THE UNIX GURU UNIVERSE AND ARE
NOT TO BE SOLD, PRINTED OR USED WITHOUT THE WRITTEN CONSENT OF THE UNIX
GURU UNIVERSE. ALL TIPS ARE "USE AT YOUR OWN RISK". UGU ADVISES THAT
ALL TIPS BE TESTED IN A NON-PRODUCTION DEVELOPMENT ENVIRONMENT FIRST.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
==========================================================================

Unix Tip: UPGRADING OPERATING SYSTEMS

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3523 - October 2, 2010

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UPGRADING OPERATING SYSTEMS

There are many cases where a vendor will tell you
that with each new upgrade of the operating system
one does not need to wipe the disk clean.

Whenever possible, and given the chance, wipe
clean the system disk with a "newfs" or "mkfs",
depending on your unix flavor.

If a version number leaps an entire number
for example, Version 5.3 -> version 6.2, it
is highly recommended that the disk be wiped
clean. In some cases it can be safe to
upgrade without wiping a system disk if the
version is not a full leap for example,
Version 5.2 -> Versions 5.3

Past history has shown that in some cases the
following could happen if a system disk wasn't
wiped clean first:

1) New versions mixed with older patches can
cause the system to become unstable.

2) Old configuration files are not compatible with
the newer O.S.

3) Some 3rd party software or device drivers wouldn't
be compatible.

4) Loss of unknown modified system files.

5) The new kernel will not be able to compile sometimes.

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==========================================================================
DISCLAIMER: All UNIX HOT TIPS ARE OWNED BY THE UNIX GURU UNIVERSE AND ARE
NOT TO BE SOLD, PRINTED OR USED WITHOUT THE WRITTEN CONSENT OF THE UNIX
GURU UNIVERSE. ALL TIPS ARE "USE AT YOUR OWN RISK". UGU ADVISES THAT
ALL TIPS BE TESTED IN A NON-PRODUCTION DEVELOPMENT ENVIRONMENT FIRST.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
==========================================================================

Unix Tip: INETD.CONF CLEAN UP

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3522 - October 1, 2010

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INETD.CONF CLEAN UP

In most cases, vendors install the /etc/inetd.conf
file pretty wide open. There are many processes in
this file that do not have to be running.

One good way to improve the systems performance is
to not run the unnecessary daemons.

If you do not plan to offer or run those
services, then comment them out and restart
inetd daemon.

Here is a list of the less common daemons, that
can turned off on workstations (Servers may
require some of these daemons).

finger
uucp
http
bootp
dhcp_bootp
tftp
ntalk
walld
...etc...

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==========================================================================
DISCLAIMER: All UNIX HOT TIPS ARE OWNED BY THE UNIX GURU UNIVERSE AND ARE
NOT TO BE SOLD, PRINTED OR USED WITHOUT THE WRITTEN CONSENT OF THE UNIX
GURU UNIVERSE. ALL TIPS ARE "USE AT YOUR OWN RISK". UGU ADVISES THAT
ALL TIPS BE TESTED IN A NON-PRODUCTION DEVELOPMENT ENVIRONMENT FIRST.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
==========================================================================