tar and gzip / bzip on a single command in AIX

This command will be helpful when you do not have an option "z" for tar. In Linux you can directly specify "z" option in tar command but in AIX, you can not ....
To compress:

"tar cvf - abc | gzip > abc.tar.gz"

"tar cvf - abc | bzip2 > abc.tar.bz2"

To uncompress:

"gunzip < abc.tar.gz | tar xvf -"

"bzip2 < abc.tar.bz2 | tar xvf -"

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List folder / directories by size in Linux / AIX

To list the directory sizes in kilo bytes and largest at the top
du -sk * | sort +0nr
du -sk * | sort -nr

To list the directory sizes in Mega bytes and largest at the top
du -sm * | sort +0nr
du -sm * | sort -nr

To list the directory sizes in kilo bytes and largest at the bottom.
du -sk * | sort +0n
du -sk * | sort -n

To list the directory sizes in Mega bytes and largest at the bottom.
du -sm * | sort +0n
du -sm * | sort -n

To list the directory sizes in human readable format (Mix of kilo, Mega and Giga bytes) and largest at the bottom
du -s *|sort -n|cut -f 2-|while read a;do du -hs $a;done


To list the size of hidden directories

du -sk .[a-z]* | sort +0nr

To list the size of all the files and directorires including hidden files and directories
du -sk .[a-z]* * | sort +0n

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SUID, SGID anh Sticky bit

Set user ID, set group ID, sticky bit

In addition to the basic permissions discussed above, there are also three bits of information defined for files in Linux:

* SUID or setuid: change user ID on execution. If setuid bit is set, when the file will be executed by a user, the process will have the same rights as the owner of the file being executed.
* SGID or setgid: change group ID on execution. Same as above, but inherits rights of the group of the owner of the file on execution. For directories it also may mean that when a new file is created in the directory it will inherit the group of the directory (and not of the user who created the file).
* Sticky bit: It was used to trigger process to "stick" in memory after it is finished, now this usage is obsolete. Currently its use is system dependent and it is mostly used to suppress deletion of the files that belong to other users in the folder where you have "write" access to.

Numeric representation
Octal digit Binary value Meaning
0 000 setuid, setgid, sticky bits are cleared
1 001 sticky bit is set
2 010 setgid bit is set
3 011 setgid and sticky bits are set
4 100 setuid bit is set
5 101 setuid and sticky bits are set
6 110 setuid and setgid bits are set
7 111 setuid, setgid, sticky bits are set

Textual representation

SUID, If set, then replaces "x" in the owner permissions to "s", if owner has execute permissions, or to "S" otherwise.

Examples:
-rws------ both owner execute and SUID are set
-r-S------ SUID is set, but owner execute is not set

SGID, If set, then replaces "x" in the group permissions to "s", if group has execute permissions, or to "S" otherwise.

Examples:
-rwxrws--- both group execute and SGID are set
-rwxr-S--- SGID is set, but group execute is not set

Sticky, If set, then replaces "x" in the others permissions to "t", if others have execute permissions, or to "T" otherwise.

Examples:
-rwxrwxrwt both others execute and sticky bit are set
-rwxrwxr-T sticky bit is set, but others execute is not set

Setting the sticky bit on a directory : chmod +t

If you have a look at the /tmp permissions, in most GNU/Linux distributions, you'll see the following:

lokams@tempsrv# ls -l | grep tmp
drwxrwxrwt 10 root root 4096 2006-03-10 12:40 tmp

The "t" in the end of the permissions is called the "sticky bit". It replaces the "x" and indicates that in this directory, files can only be deleted by their owners, the owner of the directory or the root superuser. This way, it is not enough for a user to have write permission on /tmp, he also needs to be the owner of the file to be able to delete it.

In order to set or to remove the sticky bit, use the following commands:

# chmod +t tmp
# chmod -t tmp

Setting the SGID attribute on a directory : chmod g+s

If the SGID (Set Group Identification) attribute is set on a directory, files created in that directory inherit its group ownership. If the SGID is not set the file's group ownership corresponds to the user's default group.

In order to set the SGID on a directory or to remove it, use the following commands:

# chmod g+s directory
# chmod g-s directory

When set, the SGID attribute is represented by the letter "s" which replaces the "x" in the group permissions:

# ls -l directory
drwxrwsr-x 10 george administrators 4096 2006-03-10 12:50 directory

Setting SUID and SGID attributes on executable files : chmod u+s, chmod g+s

By default, when a user executes a file, the process which results in this execution has the same permissions as those of the user. In fact, the process inherits his default group and user identification.

If you set the SUID attribute on an executable file, the process resulting in its execution doesn't use the user's identification but the user identification of the file owner.

For instance, consider the script myscript.sh which tries to write things into mylog.log :

# ls -l
-rwxrwxrwx 10 george administrators 4096 2006-03-10 12:50 myscript.sh
-rwxrwx--- 10 george administrators 4096 2006-03-10 12:50 mylog.log

As you can see in this example, George gave full permissions to everybody on myscript.sh but he forgot to do so on mylog.log. When Robert executes myscript.sh, the process runs using Robert's user identification and Robert's default group (robert:senioradmin). As a consequence, myscript fails and reports that it can't write in mylog.log.

In order to fix this problem George could simply give full permissions to everybody on mylog.log. But this would make it possible for anybody to write in mylog.log, and George only wants this file to be updated by his myscript.sh program. For this he sets the SUID bit on myscript.sh:

# chmod u+s myscript.sh

As a consequence, when a user executes the script the resulting process uses George's user identification rather than the user's. If set on an executable file, the SUID makes the process inherit the owner's user identification rather than the one of the user who executed it. This fixes the problem, and even though nobody but George can write directly in mylog.log, anybody can execute myscript.sh which updates the file content.

Similarly, it is possible to set the SGID attribute on an executable file. This makes the process use the owner's default group instead of the user's one. This is done by:

# chmod g+s myscript.sh

By setting SUID and SGID attributes the owner makes it possible for other users to execute the file as if they were him or members of his default group.

The SUID and GUID are represented by a "s" which replaces the "x" character respectively in the user and group permissions:

# chmod u+s myscript.sh
# ls -l
-rwsrwxrwx 10 george administrators 4096 2006-03-10 12:50 myscript.sh
# chmod u-s myscript.sh
# chmod g+s myscript.sh
# ls -l
-rwxrwsrwx 10 george administrators 4096 2006-03-10 12:50 myscript.sh

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How to mount a cd manually in AIX

To manually mount a cd in IBM AIX:

# mount -V cdrfs -o ro /dev/cd0 /cdrom 

Example:

mount -V cdrfs -o ro /dev/cd0 /cdrom

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Mount ISO image in AIX

First Create a filesystem with crfs command:

#/usr/sbin/crfs -v jfs -g rootvg -a size=800 -m/cd1iso -Ano -pro -tno -a frag=4096 -a nbpi=4096 -a ag=8

This command creates the /cd1iso file system on the rootvg volume group.

Now dd the "iso" image into rlv00
# dd if=image.iso of=/dev/rlv00 bs=10M

Use chfs to change the attributes of a file system:# chfs -a vfs=cdrom cd1iso
# mount /cd1iso
# cd /cd1iso

When done, remove the filesystem/unmount, enter:
# rmfs /cd1iso

This removes the /cd1iso file system, its entry in the /

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Enable remote desktop remotely

1. Run Regedit

2. Select File | Connect Network Registry

3. Enter the name of the remote computer and select Check Names

4. Go to hklm\system\currentcontrolset\control\terminal server\FdenyTSConnection=1

5. Change the FdenyTSConnection to 0

Now you should be able to connect to the remote computer using Remote Desktop.

6. Reboot the remote machine by issuing the following command in Command Prompt:

shutdown -m \\hostname –r

7. Remote Desktop for the remote computer has been enabled and listening on default Remote Desktop port for any incoming Remote Desktop Connection. For security reason, you may want to consider changing the Remote Desktop listening port. There is also plenty of freeware utility that allows user to remotely enable Remote Desktop without modifying registry.

Using PSEXEC:

psexec \\computername reg add "hklm\system\currentcontrolset\control\terminal server" /f /v fDenyTSConnections /t REG_DWORD /d 0

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