Monitor CPU Temperature on Linux (CentOS/RHEL)

lm_sensor is a tool that can monitor linux hardware - works great with 2.6 + kernel onwards

install

#yum install lm_sensors

Configure

#sensors-detect

Press YES to all prompt 

Output depend on your type of MB

=====================

Now follows a summary of the probes I have just done.
Just press ENTER to continue:

Driver `w83627ehf':
  * ISA bus, address 0xa10
    Chip `Winbond W83627DHG-P Super IO Sensors' (confidence: 9)

Driver `sbs':
  * Bus `i915 gmbus reserved'
    Busdriver `drm', I2C address 0x0b
    Chip `Smart Battery' (confidence: 5)

Do you want to overwrite /etc/sysconfig/lm_sensors? (YES/no):
Starting lm_sensors: loading module sbs w83627ehf          [  OK  ]
Unloading i2c-dev... OK
==============================

Instead of system restart - load the module (if any)by modprobe command 

#modprobe i2d-dev

you can check the modules as

# cat /etc/sysconfig/lm_sensors

Run the command to check the cpu current temperature & high/critical limit

[root@imonitor tmp]# sensors
coretemp-isa-0000
Adapter: ISA adapter
Core 0:      +23.0°C  (high = +89.0°C, crit = +105.0°C)   >> here +23 deg C is the current Temp
Core 2:      +18.0°C  (high = +89.0°C, crit = +105.0°C)

w83627dhg-isa-0a10
Adapter: ISA adapter
Vcore:       +0.90 V  (min =  +0.00 V, max =  +1.74 V)
in1:         +0.78 V  (min =  +1.27 V, max =  +0.52 V)   ALARM
AVCC:        +3.39 V  (min =  +2.98 V, max =  +3.63 V)
VCC:         +3.39 V  (min =  +2.98 V, max =  +3.63 V)
in4:         +1.30 V  (min =  +0.93 V, max =  +1.48 V)
in5:         +0.77 V  (min =  +0.06 V, max =  +0.64 V)   ALARM
in6:         +1.06 V  (min =  +0.01 V, max =  +0.03 V)   ALARM
3VSB:        +3.36 V  (min =  +2.98 V, max =  +3.63 V)
Vbat:        +3.34 V  (min =  +2.70 V, max =  +3.30 V)   ALARM
fan1:          0 RPM  (min = 112500 RPM, div = 4)  ALARM
fan2:          0 RPM  (min = 3924 RPM, div = 4)  ALARM
fan3:          0 RPM  (min = 337500 RPM, div = 4)  ALARM
fan5:          0 RPM  (min = 13775 RPM, div = 2)  ALARM
temp1:       +24.0°C  (high = -68.0°C, hyst = -123.0°C)  ALARM  sensor = diode
temp2:       +23.0°C  (high = +80.0°C, hyst = +75.0°C)  sensor = diode
temp3:      +127.0°C  (high = +80.0°C, hyst = +75.0°C)  ALARM  sensor = thermistor
cpu0_vid:   +2.050 V

if you want to see the temperature in Fahrenheit then 

#sensors -F

if you want to monitor it live then use the below command

#watch 'sensors | grep "core''

Reading

http://www.xbitlabs.com/articles/cpu/display/p4-temp.html

http://ark.intel.com/Default.aspx 

http://www.lm-sensors.org/wiki 

 http://www.cyberciti.biz/faq/howto-linux-get-sensors-information/

Ftp Access to /var/www/html for website editing [CentOS/RHEL + Vsftpd]

1. Create a group for website users , say webgroup   # groupadd webgroup
2. give them proper permissions  : chown -R root:webgroup /var/www/html
3.chmod g+s  /var/www/html    {this will help if a user "x" creates a file/dir then it will be owned by him , so set a SETGID bit to the parent directory so that any new file by default have group id as webgroup}
4. chmod 770 /var/www/html
5. usermod -aG webgroup apache


How to Set VSFTPD

#yum install vsftpd
# service vsftpd start
#chkconfig vsftpd on
# netstat -a | grep ftp


Contents of vsftpd.conf
anonymous_enable=NO
local_enable=YES
write_enable=YES

local_umask=002

dirmessage_enable=YES

xferlog_enable=YES

connect_from_port_20=YES

xferlog_std_format=YES

ftpd_banner=Hello world

chroot_local_user=YES

chroot_list_enable=YES

chroot_list_file=/etc/vsftpd.chroot_list

pam_service_name=vsftpd

userlist_enable=YES

listen=YES

tcp_wrappers=YES

Contents of vsftpd.chroot_list

webftpuser

contents of : cat /etc/pam.d/vsftpd

#%PAM-1.0

auth       required     pam_listfile.so item=user sense=deny file=/etc/vsftpd.ftpusers onerr=succeed

auth       required     pam_stack.so service=system-auth

auth       required     pam_shells.so

account    required     pam_stack.so service=system-auth

session    required     pam_stack.so service=system-auth

Monitor per core CPU utilization in Linux (CentOS/RHEL)

1. Run Top  and press numeric 1 to get core wise CUP utilization
#top
1

Other tags

 Z,B       Global: 'Z' change color mappings; 'B' disable/enable bold
  l,t,m     Toggle Summaries: 'l' load avg; 't' task/cpu stats; 'm' mem info
  1,I       Toggle SMP view: '1' single/separate states; 'I' Irix/Solaris mode

  f,o     . Fields/Columns: 'f' add or remove; 'o' change display order
  F or O  . Select sort field
  <,>     . Move sort field: '<' next col left; '>' next col right
  R,H     . Toggle: 'R' normal/reverse sort; 'H' show threads
  c,i,S   . Toggle: 'c' cmd name/line; 'i' idle tasks; 'S' cumulative time
  x,y     . Toggle highlights: 'x' sort field; 'y' running tasks
  z,b     . Toggle: 'z' color/mono; 'b' bold/reverse (only if 'x' or 'y')
  u       . Show specific user only
  n or #  . Set maximum tasks displayed

  k,r       Manipulate tasks: 'k' kill; 'r' renice
  d or s    Set update interval
  W         Write configuration file
  q         Quit

2. Use Sar

#Sar -A

 

sosreport in CentOS and RHEL >> ‘Generate debugging information for this system

# yum install sos

“sosreport” will generate a compressed a bz2 file under /tmp.

# /usr/sbin/sosreport

sosreport (version 2.2)

This utility will collect some detailed  information about the
hardware and setup of your Red Hat Enterprise Linux system.
The information is collected and an archive is  packaged under
/tmp, which you can send to a support representative.
Red Hat Enterprise Linux will use this information for diagnostic purposes ONLY
and it will be considered confidential information.

This process may take a while to complete.
No changes will be made to your system.

Press ENTER to continue, or CTRL-C to quit.
 

Press Enter

Please enter your first initial and last name [sapp1-rl]: Mr Aqua
 
Please enter the case number that you are generating this report for:dummy


  Running plugins. Please wait ...

  Completed [53/53] ...
Creating compressed archive...

 
Your sosreport has been generated and saved in:
  /tmp/sosreport-MrAqua-20120614230734-28d7.tar.xz

The md5sum is: ffc2e235390412ccade7e4a1e50428d7

Please send this file to your support representative.

You have mail in /var/spool/mail/root
 

It contains linux configuration files/all startup/shutdown scripts, all kind of current system information (dmidecode, lsmod, lspci, netstat, iptables, rpm, network routes

passwd: Authentication token manipulation error + CentOS

if you see this error then just run the "pwconv" from root prompt as shown in the example and  you will be all set.

[root@aqua ~]# passwd myuser
Changing password for user myuser.
passwd: Authentication token manipulation error
[root@aqua ~]# pwconv
[root@aqua ~]# passwd myuser
Changing password for user myuser.
New UNIX password:
Retype new UNIX password:
passwd: all authentication tokens updated successfully.
[root@aqua ~]#

SSD & CentOS 6+

SSD  & CentOS 6+

SSDs can be divided into three classes, based on throughput:

• The first class of SSDs use a PCI-Express connection, which offers the fastest I/O throughput compared to other classes. This class also has a very low latency for random access.
• The second class uses the traditional SATA connection, and features fast random access for read and write operations (though not as fast as SSDs that use PCI-Express connection).
• The third class also uses SATA, but the performance of SSDs in this class do not differ substantially from devices that use 7200rpm rotational disks.

For all three classes, performance degrades as the number of used blocks approaches the disk capacity. The degree of performance impact varies greatly by vendor. However, all devices experience some degradation.

Enabling discard support is most useful when there is available free space on the file system, but the file system has already written to most logical blocks on the underlying storage device.

At present, ext4 is the only fully-supported file system that supports discard. 

To enable discard commands on a device, use the mount option discard. For example, to mount /dev/sda2 to /data with discard enabled, run:

mount -t ext4 -o discard /dev/sdb1 /data

By default, ext4 does not issue the discard command.

This is mostly to avoid problems on devices which may not properly implement the discard command. The Linux swap code will issue discard commands to discard-enabled devices, and there is no option to control this behavior.

There are basically two big things to do

-        enable discard/trim support in the file system

-       Limit write operations to the SSD. You want to enable discard to deal with underlying drive specific performance degradation that will happen over time

Move /tmp to ram.  This depends on how much ram you have and how much /tmp space you use, but it really helps to limit writes to the SSD

Change the mount options for your ext4 filesystem

-       change data from the default of ordered to writeback. This reduces the journal data to meta-data only, thus limiting writes.

-       change the commit value from the default of 5 seconds to 10, or 15. This gets you a 2 to 3x write savings, though you risk losing a bit more data if you lose power.

-       If you don't need access time records (mtime and ctime should be enough for most folks) disabling atime will also limit write operations. 

Ex:   /dev/sdb1        /      ext4     defaults,discard,data=writeback,noatime,commit=15     1 1

A/ mount file systems with the "noatime" option.
"noatime" prevents the file system from updating file access times.
"noatime" includes "nodiratime" (prevents directory access time updates).

Consider whether you need journals

            File system journals make file system reconstruction (fsck for
example) possible, and running without any journal makes catastrophic
file system failure far more likely. On the other hand, journals
require extra write operations, Sometimes it's easy enough to
reconstruct a file system that it's not worth the cost in terms of SSD
write operations.

echo "noop" > /sys/block/sda/queue/scheduler
in /etc/rc.d/rc.local.

OR

one can eliminate journaling altogether by doing this to a unmounted or read-only ext4
tune2fs -O ^has_journal /dev/sda1

 Then there will be no journal. While you are at it the command:
tune2fs -r 1024 /dev/sda1
will reduce the root-reserved blocks to 1k (4MB) 

Get rid of /tmp

Put it on ramdisk. The X11 server makes a huge number of tiny
writes to /tmp and if these flush to disk at a high rate it creates a
load of writes. Adding this line to /etc/fstab does the trick.

none /tmp tmpfs defaults 0 0

To enable trim, use the "discard' mount option in fstab for all mounted partitions from the SSD. The "swap" partition automatically uses TRIM. For example from /etc/fstab ....

Code:

UUID=ffc6a6fc-1bf3-4f25-ab17-067b0515e85a /   ext4    noatime,discard,data=writeback 1 1

UUID=24941fe7-6d23-4969-951e-0872d4b81b0e /home      ext4    noatime,discard,data=writeback 1 2

UUID=2bbebe51-c0f8-4296-ba0a-e715bf84dc67 swap       swap    defaults                       0 0

Few useful Commands

fdisk -u -l /dev/sdX

cat /sys/block/sda/queue/scheduler

Use iotop -oPa and sort by disk writes to see how much programs are writing to disk

Using “tune2fs –l /dev/sdb”, we can see the file system block size is 4KB with journal turned on.

Using “more /sys/fs/ext4/sdc/lifetime_write_kbytes” to see how much has been written to the disk so far

stop all application/System  services on the box,

unmount sdbX and sdcX

run tune2fs to set stride, stripe-width options

change mounting option on sdb, sdc to use noatime

mount again

start application/System services 

mkfs.ext4 -b 1024 -E stride=128,stripe-width=128 -O ^has_journal /dev/sda1

mkfs.ext4 -b 4096 -E stride=32,stripe-width=32 /dev/sda3 

Ref

http://www.void.gr/kargig/blog/2012/01/11/linux-ssd-partition-alignment-tips/

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/newmds-ssdtuning.html

http://blog.nuclex-games.com/2009/12/aligning-an-ssd-on-linux/  (good read)

https://wiki.archlinux.org/index.php/Solid_State_Drives (good read)

http://www.xbitlabs.com/articles/storage/display/intel-x25m-ssd_2.html

http://www.xbitlabs.com/articles/storage/display/intel-x25m-ssd_2.html

Exchange 2007 DG & List of all forwarding address list

Fetch the DG members from Exchange 2007

Get-DistributionGroupMember –identity “group name” | ft name, primarysmtpaddress | Export-CSV c:members.csv

Find all users with Forwarding Address is set

Get-Mailbox | Where {$_.ForwardingAddress -ne $null} | Select Name, ForwardingAddress, DeliverToMailboxAndForward c:/myfile.txt 

Mail Server - TODO

- Check for the open relay  , it should not configured for that :)
- Restrict the application servers by IP to relay email. you can use to test (http://www.abuse.net/relay.html )
- Check for the DNS and Reverse DNS
- Use SPF
- Use AntiSpam & Antivirus tools
- Monitor incoming and outgoing tools.
- Check RBL for the mail server blacklisting
-

Partition Alignment

#sudo fdisk -luc

turn off MSDOS mode

#sudo fdisk -H 32 -S 32 -cu /dev/yourdisk

1 Gigabyte = 2,097,152 sectors
1 Megabyte = 2,048 sectors


total_sectors / 2,097,152 (sectors in 1GB) = Total Gigabytes
remaining_sectors / 2,048 (sectors in 1MB) = Total Megabytes

Example
2,097,152 X 25 = 52,428,800 (25GB)
2,048 X 750 = 1,536,000 (750MB)
(2,097,152 X 12) + (2,048 X 500) = 26,189,824 (12GB+500MB)


Remember: If you're aligning partitions make sure to start at a sector evenly divisable by 512.
When asked for the size of your partition you'll need to prefix a + to your sectors.
Your last partition may consume the rest of the disk without a worry.


Alignment.

thumb rule is all about your partition starting at a sector evenly divisable by 512. The size of your partition and/or where it ends does not matter. As long as your partition starts at a sector divisable by 512 you're good.

If you had the following partitions sizes ready to go and you could sacrifice 512 bytes per partition without a worry, you subtract 1 sector from each partition. Doing it this way insures no gaps between partitions.


52,428,800 (25GB) - 1 sector = 52,428,799
1,536,000 (750MB) - 1 sector = 1,535,999
26,189,824 (12GB+500MB) - 1 sector = 26,189,823


start at 2,048 because this is the most common start sector in almost all guides. The following example assumes you don't mind shaving 512 bytes per partition by subtracting 1 sector each. In other words you don't need the absolute size and in that process create no gaps between partitions.


Start       End
2,048       +52,428,799  # This partition ends at 52,430,847, the next partition starts at 52,430,848 (evenly divisable by 512)
52,430,848  +1,535,999   # This partition ends at 53,966,847, the next partition starts at 53,966,848 (evenly divisable by 512)


The following example assumes you do mind shaving 512 bytes and want absolute sizes. If you need an absolute size per partition and cannot subtract 1 sector per partition you simply start your next partition at a sector evenly divisable by 512.


Start       End
2,048       +52,428,800  # This partition ends at 52,430,848, our next partition cannot start there. It will start at 52,430,848 + 512 = 52,431,360 (evenly divisable by 512)
52,431,360  +1,536,000   # This partition ends at 53,967,360, our next partition cannot start there. It will start at 53,967,360 + 512 = 53,967,872 (evenly divisable by 512)
53,967,872  +26,189,824  # This partition ends at 80,157,696, our next partition cannot start there. It will start at 80,157,696 + 512 = 80,158,208 (evenly divisable by 512)

Reinstalling the agents on ESX

Reinstalling the agents on ESX

1. Disconnect the ESX host in vCenter Server. Right-click the host and click Disconnect.
2. Log in as root to the ESX host using an SSH client.
3. Run this string of commands in the SSH session:
   
   service mgmt-vmware stop && service vmware-vpxa stop && service vmware-vmkauthd stop && service xinetd restart && rpm -qa | grep -i vpxa | awk '{print $1}' | xargs rpm -ef $1 && userdel vpxuser && rpm -qa | grep -i aam | awk '{print $1}' | xargs rpm -ef $1 && service mgmt-vmware start && service vmware-vmkauthd start
   
   Note: This is a concatenated list of commands strung together with the "&&" operator. This is useful in stringing together multiple commands as the next command does not start until the previous one has completed successfully.
   
   These are the commands you are running:
   
   • service mgmt-vmware stop && service vmware-vpxa stop && service vmware-vmkauthd stop && service xinetd restart stops the management services for the service console.
   • rpm -qa | grep -i vpxa | awk '{print $1}' | xargs rpm -ef $1 removes the vpxa agent.
   • userdel vpxuser removes the vpxa user that is installed once you connect the host to vCenter Server.
   • rpm -qa | grep -i aam | awk '{print $1}' | xargs rpm -ef $1 removes the AAM RPM (HA) which is reinstalled when you configure HA.
   • service mgmt-vmware start && service vmware-vmkauthd start restarts the services.
   • vmware-cmd -l lets you know when hostd is up and running so that you can reattach it to vCenter Server.
     
   Note: When you see a list of virtual machines output, the command sequence is complete.
   
4. Log in to the vCenter Server using VMware Infrastructure/vSphere Client.
5. Choose the ESX host from the Inventory.
6. Right-click on the ESX host and click Connect. This step initiates a re-install of the agent.

Create ext4 partition

1. Upgrade your system: yum update 
2. Format the partition: mkfs.ext4 /dev/sdxY (replace sdxY with the device to format (e.g. sda1))
3. Mount the partition
4. Add an entry to /etc/fstab, using the filesystem 'type' ext4 

 df -T | awk '{print $1,$2,$NF}' | grep "^/dev"

Format an external/Second HDD with ext4

First,  delete any existing partition and create a new Linux partition using fdisk:

1	# fdisk /dev/sdb

Assuming /dev/sdb is the external or second hard disk. Use d to delete the partition and use n to create a new partition. 83 is the ID of the native Linux partition.
Them,  use mkfs.ext4 to format the partition with ext4:

1	# mkfs.ext4 /dev/sdb1

Note that mkfs.ext4 expects a partition as its argument.
use tune2fs to adjust some parameters:

1 2	# tune2fs -m 0 /dev/sdb1 # tune2fs -L secondDisk01 /dev/sdb1

The -m option is for adjusting the percentage of reserved blocks. The reserved blocks are used by privileged processes which is by default 5% of the hard disk size. Since I’m using the external/second hard disk solely as a storage, I set this to 0 so I can also use those 5% for storage. The -L option is for labeling the filesystem.

Free NX [Error: Call to bind failed for font TCP port 11000]

Info: Proxy running in client mode with pid '98196'.

Session: Starting session at 'Mon Apr 30 18:22:52 2012'.

Warning: Connected to remote version 3.4.0 with local version 3.5.0.

Info: Connection with remote proxy completed.

Error: Call to bind failed for font TCP port 11000. Error is 112 'Address already in use'.

Session: Session terminated at 'Mon Apr 30 18:22:52 2012'.

This can happen if you have multiple NX connection to multiple machine.

sometime it can be due to the base display number. you can change that with

some other port. but make sure that port is not used by some other application.

 Or

Just start one connection at a time with nx client instead of multiple 

The setting is in the file # cat  /etc/nxserver/node.conf

# The base display number from which sessions are started.

#DISPLAY_BASE=1000

tar zcvf ~/ssh_freenx_config.tgz $(rpm -ql openssh-server freenx | grep etc)

How to Setup NTP server and Client (CentOS/RHEL)

NTP (Network time protocol) is used to  synchronize a computer's time in a local network (usually behind firewall )with another reference time source.

Steps:
1. Install NTP package
2. configure ntp.conf
3. start ntpd daemon
4.check   with ntpq -n

check the correct

cat /etc/sysconfig/clock

rpm -qa ntp

one US and one Canada NTP Server

http://www.pool.ntp.org/zone/north-america

http://www.pool.ntp.org/zone/ca

http://support.ntp.org/bin/view/Servers/StratumOneTimeServers


vim /etc/ntp.conf
# permit the source to query or modify the service on this system.
restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

# Permit all access over the loopback interface.  This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 127.0.0.1
restrict -6 ::1

# Hosts on local network are less restricted.
restrict 10.1.1.0 mask 255.255.255.0 nomodify notrap
restrict 10.10.10.0 mask 255.255.255.0 nomodify notrap

# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server time-a.nist.gov

server time-nw.nist.gov

server 0.ca.pool.ntp.org
server 1.ca.pool.ntp.org
# Undisciplined Local Clock. This is a fake driver intended for backup
# and when no outside source of synchronized time is available.
#server 127.127.1.0     # local clock
fudge   127.127.1.0 stratum 10



#service ntpd restart



 ntpdate -u  0.ca.pool.ntp.org

 ntpq -p