What is the difference between "su -" and "su" ?

The main difference between su - and su is that the former makes the shell a login shell. This is very important especially if the user is going to su from a regular user account to a root (superuser) account. Normal users do not usually have /sbin/ and /usr/sbin/ in their search path. Therefore if a normal user wants to execute the command ifconfig, for example, after doing su, he usually gets the error message:

bash: ifconfig: command not found

With su -, on the other hand, root's .bashrc and .bash_profile and other special environment settings get sourced and this puts the sbin directories into the search path. Below is a sample session:

[testuser@localhost ~]$ su
Password:
[root@localhost testuser]# echo $PATH
/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/home/testuser/bin
[root@localhost testuser]# ifconfig
bash: ifconfig: command not found
[root@localhost testuser]# exit
exit
[testuser@localhost ~]$ su -
Password:
[root@localhost ~]# echo $PATH
/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin
[root@localhost ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:A0:CC:39:75:41
inet addr:192.168.44.146 Bcast:172.16.45.255 Mask:255.255.254.0
inet6 addr: fe80::2a0:ccff:fe39:7541/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:21619559 errors:1 dropped:0 overruns:0 frame:87
TX packets:21190195 errors:4 dropped:0 overruns:4 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1509569968 (1.4 GiB) TX bytes:2280347397 (2.1 GiB)
Interrupt:177 Base address:0x6800

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:6159 errors:0 dropped:0 overruns:0 frame:0
TX packets:6159 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3784618 (3.6 MiB) TX bytes:3784618 (3.6 MiB)

Change hostname in Linux without rebooting server

Change hostname in Linux without rebooting server

First you need to find out your hostname, you can do this with

$ hostname
localhost.localdomain
$

Edit /etc/hosts

You need to edit /etc/hosts and add a line for your host name

$ cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost
$

My new server IP is 192.168.1.1, i need to assign it hostname fedora.redhat.com, to do this, i have edited /etc/hosts as follows.

# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost
192.168.1.1 fedora.redhat.com fedora

Edit /etc/sysconfig/network

First lets see what is in the file

$ cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=localhost.localdomain
$

To change servers hostname to fedora.redhat.com, change the file as follows.

$ cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=fedora.redhat.com
$

$/bin/hostname fedora.redhat.com

$service syslog restart

after you can logout and login back

RedHat/CentOS Cluster HP ilo

1. root#mkqdisk -c /dev/sda1 -l qdisk_rac
2. root#chkconfig --level 345 qdiskd on
3. root#service qdiskd start
4. root#system-config-cluster
5. Cluster Name : apache-cluster and selected quorum disk with following options
Interval = 1
TKO = 10
votes =1
Minimum score = 3
Device = /dev/sda1
Label = qdisk_rac
6. Quorum Disk Heuristic
Program = ping -c 2 10.10.10.1
Score =1
Interval = 2
7. Add new node to cluster
Node Name = node1.example.com
Quorum votes = 1
Node Name = node2.example.com
Quorum votes = 1
8. New Fence Device
HP ILO Device
Name = ILOGB89xxxxxx
user = manage
password = manage
Hostname = 10.10.10.100
HP ILO Device
Name = ILOGB88xxxxxx
user = manage
password = manage
Hostname = 10.10.10.101

9. selected Node1 and "Manage fencing for this node"
Add New Fencing level -> Add Fencing to this Level. selected ILOGB89xxxxxx

10. selected Node2 and "Manage fencing for this node"
Add New Fencing level -> Add Fencing to this Level. selected ILOGB88xxxxxx
11. Created failover domains "failover-cluster" and selected
"node1.example.com and node2.example.com" from menu, and selected
"
"Restrict to this Failover Domain"

12. Create Resource
New Resource = Apache Server
Name = Apache HTTP Server service
Server Root = /etc/httpd
Config File = /etc/httpd/conf/httpd.conf
httpd options = /etc/rc.d/init.d/httpd

13. Create a new Resource "File system"
Name = httpd-content
File System type = ext3
Mount point = /var/www/html
device = /dev/sdb1

14. Create a new Resource "IP "
10.10.10.200

15. Create a New Service "Web-Service"
Failover Domain = failover-cluster
And selected "Add shared resource to this service"
A. Apache HTTP Server Service
B. Httpd-Content
C. IP Address (10.10.10.200)

16
#[node1@node1]scp /etc/cluster/cluster.conf node2:/etc/cluster/cluster.conf

17

#md5sum /etc/clsuter/cluster.conf

541b1dc67392b18aad7e1df3612a6afe cluster.conf (both node )

on both node

18
#service cman start
#service rgmanager start

19

#chkconfig cman on
#chkconfig rgmanager on

20

# fence_ilo -a 10.163.16.31 -l Administrator -p password -o status -v

# fence_ilo -a 10.163.16.31 -l Administrator -p password -o reboot -v

FTP server

[1] Build FTP server to transfer files. Install and configure vsftpd for it.
[rajat@rajat ~]#
yum -y install vsftpd

Loading mirror speeds from cached hostfile
Reading repository metadata in from local files
Parsing package install arguments
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Downloading header for vsftpd to pack into transaction set.
vsftpd-2.0.5-10.el5.i386. 100% |========================| 16 kB 00:00
---> Package vsftpd.i386 0:2.0.5-10.el5 set to be updated
--> Running transaction check

Dependencies Resolved

===========================================================
Package
Arch
Version
Repository
Size

===========================================================
Installing:
vsftpd
i386
2.0.5-10.el5
base
137 k


Transaction Summary
===========================================================
Install
1 Package(s)

Update
0 Package(s)

Remove
0 Package(s)


Total download size: 137 k
Downloading Packages:
(1/1): vsftpd-2.0.5-10.el
100% |====================| 137 k 00:00

Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing: vsftpd
#################################### [1/1]


Installed: vsftpd.i386 0:2.0.5-10.el5
Complete!
[rajat@rajat ~]#
vi /etc/vsftpd/vsftpd.conf


anonymous_enable=
NO
// line 12: no anonymous


ascii_upload_enable=YES
// line 79: make valid

ascii_download_enable=YES
(permit ascii mode transfer)


chroot_list_enable=YES
// line 94: make valid


(enable chroot list)

chroot_list_file=/etc/vsftpd/chroot_list
// line 96: make valid


(chroot list file)

ls_recurse_enable=YES
// line 102: make valid


chroot_local_user=YES
// bottom: enable chroot

local_root=public_html
// root directory

use_localtime=YES
// use local time


[root@www ~]#
vi /etc/vsftpd/chroot_list


fedora
// write users you permit


[root@www ~]#
/etc/rc.d/init.d/vsftpd start

Starting vsftpd for vsftpd:
[ OK ]