RHEL

Setting a Cron Job to Run at the End of the Month

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This is a method to be able to run a cron job on the last day of month, as this is not easily supported.  This method will support any month (from 28 days to 31 days), although you could run this every day with no consequence.  It utilizes an expression that takes the current day (plus one day forward in the future) as a number minus the current day as a number.  If the value is less than or greater than 0, then the command will run.

For example, if today is the 31st of the month, the expression will add one day in the future, so the first number would be “1”, the second number would be “31” – therefore the value is -le 0, so the command will run.

0 23 28-31 * * [ $(expr $(date +\%d -d '1 days') - $(date +\%d) ) -le 0 ] && echo true
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comm – utility for easily comparing files (better than diff)

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Comm is a very useful GNU program that is better than diff for finding unique lines between two given files. A good example would be one file with a big list of IP addresses, with another file that has a small list of IP addresses. In this example, the IP addresses in the small list are presumed to be present in the big list, but short of doing an advanced script using find, this is a quick and clean way to find the duplicates.

With no options, produce three-column output. Column one contains lines unique to file1, column two contains lines unique to file2, and column three contains lines common to both files.

-1 suppress lines unique to file1
-2 suppress lines unique to file2
-3 suppress lines that appear in both files

NOTE: The files MUST be sorted first, or the results will not be accurate.

##################################

contents of file1:
192.168.1.0
192.168.1.1
192.168.1.4
192.168.1.5
192.168.1.6
192.168.1.7
201.44.32.4
201.44.32.5
201.44.32.8
201.44.32.9

contents of file2:
192.168.1.1
192.168.1.5
201.44.32.5
201.44.32.8

#################################

Example (to find only the unique IP address in file1)

comm -3 file1 file2

# output
192.168.1.0
192.168.1.4
192.168.1.6
192.168.1.7
201.44.32.4
201.44.32.9

Joining RedHat Servers to Active Directory

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Joining Redhat servers to AD domain
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

yum install samba3x
yum install winbind

vim /etc/nsswitch

=================================
passwd: files winbind
shadow: files winbind
group: files winbind
=================================

vim /etc/samba/smb.conf

===================================
workgroup = DOMAINNAME
password server = x.x.x.x
realm = DOMAINNAME.COM
security = ads
idmap uid = 10000-20000
idmap gid = 10000-20000
winbind separator = +
template homedir = /home/%D/%U
template shell = /bin/bash
winbind use default domain = false
winbind offline logon = false
====================================

net ads join -U user@domainname.com