Unix and Linux Tips

Kamis, 10 September 2009

Unix Tip: FIND THE HOG

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3139 - September 10, 2009

http://www.ugu.com/sui/ugu/show?tip.today

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FIND THE HOG

Hot Tip for Space Cops: (aren't we all?)

If your users keep using up all the space in your home directory, here is a way to apprehend the top offenders.

cd /home
du -ks *|sort -nr|pg

(Note: The "k" option may not be necessary in non-posix systems.)This string will show you all the directory sizes in order, largest first. Now if you are going to do a little cleanup yourself, in one of those directories run:

ls -ls|sort -nr|pg

This will list files by size largest first. That way when you do your compress, move, or remove, you may actually reclaim a significant amount of space.

This tip generously supported by: uspncjpf@ibmmail.com

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Rabu, 09 September 2009

Unix Tip: KEEP THE USERS OFF WITH NOLOGIN

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3138 - September 9, 2009

http://www.ugu.com/sui/ugu/show?tip.today

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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.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Selasa, 08 September 2009

Unix Tip: KILL A USER, IN THE UNIX SENSE

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3137 - September 8, 2009

http://www.ugu.com/sui/ugu/show?tip.today

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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.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Senin, 07 September 2009

Unix Tip: JUST THE DIRECTORIES

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3136 - September 7, 2009

http://www.ugu.com/sui/ugu/show?tip.today

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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"'

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Minggu, 06 September 2009

Unix Tip: LOCK THAT FILE DOWN

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3135 - September 6, 2009

http://www.ugu.com/sui/ugu/show?tip.today

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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!

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Sabtu, 05 September 2009

Unix Tip: UMOUNT BUSY DEVICES

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3134 - September 5, 2009

http://www.ugu.com/sui/ugu/show?tip.today

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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.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Jumat, 04 September 2009

Unix Tip: UPGRADING OPERATING SYSTEMS

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3133 - September 4, 2009

http://www.ugu.com/sui/ugu/show?tip.today

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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.

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