How much swap space should the Linux/Redhat system have?

Swap space in Linux is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space. While swap space can help machines with a small amount of RAM, it should not be considered a replacement for more RAM. Swap space is located on hard drives, which have a slower access time than physical memory. Swap space can be a dedicated swap partition (recommended), a swap file, or a combination of swap partitions and swap files.

However, modern systems often include hundreds of gigabytes of RAM. As a consequence, recommended swap space is considered a function of system memory workload, not system memory.

Amount of RAM in the system	Recommended swap space	Recommended swap space if allowing for hibernation
⩽ 2 GB	2 times the amount of RAM	3 times the amount of RAM
> 2 GB – 8 GB	Equal to the amount of RAM	2 times the amount of RAM
> 8 GB – 64 GB	At least 4 GB	1.5 times the amount of RAM
> 64 GB	At least 4 GB	Hibernation not recommended

Setting Access Permissions on Shared Folders for View Persona Management

Setting Access Permissions on Shared Folders for View Persona Management

View Persona Management and Windows roaming profiles require a specific minimum level of permissions on the user profile repository. View Persona Management also requires that the security group of the users who put data on the shared folder must have read attributes on the share.

Set the required access permissions on your user profile repository and redirected folder share.

Minimum NTFS Permissions Required for the User Profile Repository and Redirected Folder Share

User Account	Minimum Permissions Required
Creator Owner	Full Control, Subfolders and Files Only
Administrator	None. Instead, enable the Windows group policy setting, Add the Administrators security group to the roaming user profiles. In the Group Policy Object Editor, this policy setting is located in Computer Configuration\Administrative Templates\System\User Profiles\.
Security group of users needing to put data on share	List Folder/Read Data, Create Folders/Append Data, Read Attributes - This Folder Only
Everyone	No permissions
Local System	Full Control, This Folder, Subfolders and Files

Share Level (SMB) Permissions Required for User Profile Repository and Redirected Folder Share

User Account	Default Permissions	Minimum Permissions Required
Everyone	Read only	No permissions
Security group of users needing to put data on share	N/A	Full Control

VNX Pool Capacity, Tier information, FAST VP Operation status

> To see Pool Capacity

naviseccli -h IP storagepool -list -tiers

> FAST VP AutoTier operation status/details

naviseccli -h ip autotiering -info -opstatus

Requirements ESRS IP Client:

Requirements ESRS IP Client:
 1. Dedicated VM with Windows 2003/08 server
 2. A Static IP network with Internet connectivity
3. Network connectivity between the servers and EMC devices to be managed by ESRS IP
 4. Internet connectivity to EMC’s ESRS infrastructure by using outbound port 80, 443 and 8443
 5. VC++, .Net Framework (min 2.0)
 6. Port number 25 needs to be open from ESRS IP Client machine to SMTP Server

EMC Powerpath

• powermt check ( – select option –a ) ( This is needed when you reboot the server Mostly for patching do – Disk Management Rescan and run the command to clear dead paths ) • powermt update lun_names ( This is needed when LUN names is to be updated and you have to update in the system to refresh same)

Reference

https://community.emc.com/docs/DOC-16349

Reconfiguring Storage Processor (SP) IP address using Navisphere Manager

CLARiiON CX Series,CLARiiON iSCSI Array.

Description:

Procedure to reconfigure SP IP address using Navisphere Manager.

Resolution:

The storage processor (SP) IP address can only be set through the /setup page. Please follow the steps give below.

If this procedure is done with active hosts attached to the array, ensure that there are no single HBA-attached hosts and that failover software is configured on each multi HBA attached host. SPs will reboot each time the IP address change is submitted.   Wait to change the other SP's IP address until the first SP has rebooted.

1.        If the storage system to be reconfigured is the domain master, select a new domain master before proceeding.

2.        Make sure both SPs for which you want to change IP addresses are connected to the network

3.        If the array on which you want to set or cannot set the IP address ("problem array") is in a domain with other arrays, open Navisphere Manager on one of the other arrays and remove it from the domain using the Configure Domain dialog.

4.        Open the setup page for SP A <SP A IP address/setup> on the array.

5.        Reset security and domain information for SP-A by pressing the "Reset Security" button.  Select "Yes" and "Submit" to confirm.

6.        Re-open the setup page for SP A on the array and restart the Management Server by pressing the "Restart Management Server" button.  Select "Yes" and "Submit" to confirm.

7.        Open the setup page for SP B <SP B IP address/setup> on the array.

8.        Reset security and domain information for SP B by pressing the "Reset Security" button.  Select "Yes" and "Submit" to confirm.

9.        Re-open the setup page for SP B on the array and restart the Management Server by pressing the "Restart Management Server" button.  Select "Yes" and "Submit" to confirm.

10.     Once the Management Server on SP A and SP B has been restarted, security and domain information will be in an uninitialized state.  You should now be able to set the IP addresses using the following steps

11.     Open a browser and go to <Current SP A IP address/setup> 

12.     In the IP address field change the current SP A IP address to the new SP A IP address and click "Apply Settings". SP A will reboot which may take up to five minutes to complete

13.     Go back to SP A's setup page using the new SP A IP address <New SP A IP Address/setup>

14.     Open a browser and go to <Current SP B IP address/setup>

15.     In the IP address field enter SP B's new IP address and in the Peer IP Address field enter SP A's new IP address and click "Apply Settings". SP B will reboot which may take up to five minutes to complete.

16.     Go back to the SP B setup page <new SP B IP Address/setup>  and click "Restart Management Server". Select "Yes" and "Submit" on the pop up screen.

17.     Go to SP A setup page <New SP A IP Address/setup> (You may already be there due to step number 12)  and click "Restart Management Server".  Select "Yes" and "Submit" on the pop up screen.   This will update the peer IP address on SP A.

18.     If the array will be back in a domain with other arrays, re-add  it to the existing domain.  Security will automatically be initialized by obtaining the necessary information from the domain master. If it was originally in the domain and it was the domain master you can now select it as the domain master again.  If the array is not to be in a domain, open Navisphere Manager on SP A of the array. You should now be prompted to initialize security.  Select "Yes" and add a global username and password. 

How to migrate Clariion to VNX using SANCopy (naviseccli)

SANCopy syntax:

naviseccli -h -create -name name <-incremental>
[-srcwwn srcwwn|
-srclun srcspname srcNumOrSnapshotName <-device devicename="">|
-srcportwwn srcportwwn srclunnumber]
[-destwwn destwwns|
-destlunnumber destspname destlunnumber <-device devicename="">|
-destportwwn destportwwn destlunnumber]
<-changesonly> <-verify> <-start> <-throttle 1-10="">
<-linkbw linkbw=""> <-latency latency=""> <-o>

Example:
navicli -h sancopy -create -name -srcwwn xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx destlunnumber -verify

Start SANCopy:

naviseccli -h sancopy -start -name

How to see the EMC ECC Bundle Update version?

What update bundle? You can check this from the ECC\exec\MGA610\MGA.ini file on agent host if you cannot locate it in the console.

Memory usage is very high on Redhat Linux

# cat free

             total       used       free     shared    buffers     cached

Mem:      24674784   24576836      97948          0     351244   21165268

-/+ buffers/cache:    3060324   21614460<<<<-----actual buffers="" cached="" free="" memory="" p="">

Swap:     25165808    1084452   24081356

    Total Physical Memory = 24674784 KB = 24096 MB

    Physically Used Memory = 24576836 KB = 24000 MB

    Actual used memory = 3060324 KB = 2988 MB = ~3 GB

    buffers = 351244 KB = 343 MB

    cached = 21165268 KB = 20669 MB = ~20 GB

    Physically Free Memory = 97948 KB = 95 MB

    Memory free for Applications = 21614460 KB = 21107 MB = ~20 GB

The items to note here are:

= + +

= - - -

= -

 

by Applications> = - -

The philosophy in Linux is that an unused resource is a wasted resource. The kernel therefore will use as much RAM as it can to cache information from your local and remote filesystems and disks. This builds up over time as reads and writes are done on the system trying to keep the data stored in RAM as relevant as possible to the processes that have been running on your system.

This caching is reported by the system as the sum of two numbers, buffers and pagecache. The cache is reclaimed, not at the time of process exit (you might start up another process soon that needs the same data), but upon demand - i.e. When you start a process that needs a lot of memory to run, the Linux kernel will reclaim memory that had been storing cached data and give it to the new process.

Refer below article for detail information on this:

What is cache memory and why is memory utilization high for cache memory?

https://access.redhat.com/knowledge/solutions/67610

Why is so much of my memory used by cache?

https://access.redhat.com/knowledge/solutions/55455

ITIL

ITIL

* Companies want to concentrate on their core business. so non-core businesses are outsourced

to other vendors (service providers) to avoid those disturbances.
example, ICICI bank's core business is financial banking, ICICI does not want to have head ache

in managing their datacenter and the application which supports their core banking work.
so ICICI decides to outsource the backend infrastructure to other companies (service providers

like IBM, HP, TCS, Infosys, Unisys,...)

for example, now ICICI choose TCS to give support. what next?
The process and procedures should be in place.
both ICICI and TCS would sit and define the SLA (Service Level Agreement) which covers all the

topics like what are all to be supported by TCS. i.e, what OS and what applications?

at the same time, ICICI wants the every work done by TCS to be recorded like,
    what is the work?
    what is the date and time executed?
    who performed?
    and its result (success/failure)?
so this way, ICICI will have good history about the changes in their servers or applications.

This history can be used if required.

So here it comes ITIL.
*  The Information Technology Infrastructure Library (ITIL) is a set of best practices that may

be used to deliver high quality IT services.
ITIL is best practice guidance and the only best practice framework for effectively managing

service management in IT, ITSM.

ITIL Benefits:
1. To align IT with the business
2. Reduce cost of operations
3. Improves quality of service
4. Delivers consistent IT services
5. Provides guidance for all types of organisation

There are 12 modules in ITSM. Important are,
1. Incident Management
2. Problem Management
3. Change Management

* An Incident is a system failure or error in the system. This may be a full disk (file system

full), a broken server (server down), or any application crash, etc. These are isolated one-time

events that have procedures for handling and fixing. These are managed under Incident Management.

*  If the same type of incidents for a same application or for a same server are geneated, this

is to be considered as a Problem. every problem would have a reason what it caused and the

solution. i.e., root cause and the solution.
These are managed under Problem Management which helps to avoid further future same typr of

incidents.

* Managing an Incident means fixing the broken system to get it working as soon as possible.

While managing a Problem means finding the underlying root causes so that the Incidents do not

happen again or as often.


*  Once we found the reason (root cause) of a problem and solution, the solution has to be

implemented. so there is a change in server configuration or application or OS.
These changes can not be done straight away. because the implementer of the change may not know

the impact of the change. Impact means application outage, future issues for other teams, etc.
So all the relevant teams would join together, discuss about the change and finally approve the

change. so Change would be implemented after the approval on a given date and time.
These processes are managed through change module.


*  ITIL is not a tool, it is a set of rules and the best practices.
By considering these rules, some companies designed software to use these incident, problem,

change management best practices. Those softwares are,
1. BMC Remedy
2. Peregrine
3. osticket
4. Altris

* BMC Remedy Versions:
Remedy 6
Remedy 7.1
Remedy 7.6

List of Unix/Linux Signals

A list of signals and what they mean
•These were all recorded from a Linux i386 system. Numbers may vary between platforms.
•Linux uses signals 34-64 for its real-time system which we are not interested in.
•“man 7 signal” gives the official manual page on signals.
•This is a fairly exhaustive list of signals. Only some of them will arise in the context of the make program.

1
SIGHUP
If a process is being run from terminal and that terminal suddenly goes away then the process receives this signal. “HUP” is short for “hang up” and refers to hanging up the telephone in the days of telephone modems.
2
SIGINT
The process was “interrupted”. This happens when you press Control+C on the controlling terminal.
3
SIGQUIT
4
SIGILL
Illegal instruction. The program contained some machine code the CPU can't understand.
5
SIGTRAP
This signal is used mainly from within debuggers and program tracers.
6
SIGABRT
The program called the abort() function. This is an emergency stop.
7
SIGBUS
An attempt was made to access memory incorrectly. This can be caused by alignment errors in memory access etc.
8
SIGFPE
A floating point exception happened in the program.
9
SIGKILL
The process was explicitly killed by somebody wielding the kill program.
10
SIGUSR1
Left for the programmers to do whatever they want.
11
SIGSEGV
An attempt was made to access memory not allocated to the process. This is often caused by reading off the end of arrays etc.
12
SIGUSR2
Left for the programmers to do whatever they want.
13
SIGPIPE
If a process is producing output that is being fed into another process that consume it via a pipe (“producer | consumer”) and the consumer dies then the producer is sent this signal.
14
SIGALRM
A process can request a “wake up call” from the operating system at some time in the future by calling the alarm() function. When that time comes round the wake up call consists of this signal.
15
SIGTERM
The process was explicitly killed by somebody wielding the kill program.
16
unused
17
SIGCHLD
The process had previously created one or more child processes with the fork() function. One or more of these processes has since died.
18
SIGCONT
(To be read in conjunction with SIGSTOP.)
If a process has been paused by sending it SIGSTOP then sending SIGCONT to the process wakes it up again (“continues” it).
19
SIGSTOP
(To be read in conjunction with SIGCONT.)
If a process is sent SIGSTOP it is paused by the operating system. All its
No. Short name What it means
state is preserved ready for it to be restarted (by SIGCONT) but it doesn't
get any more CPU cycles until then.
20 SIGTSTP Essentially the same as SIGSTOP. This is the signal sent when the user hits
Control+Z on the terminal. (SIGTSTP is short for “terminal stop”) The
only difference between SIGTSTP and SIGSTOP is that pausing is
only the default action for SIGTSTP but is the required action for
SIGSTOP. The process can opt to handle SIGTSTP differently but gets no
choice regarding SIGSTOP.
21 SIGTTIN The operating system sends this signal to a backgrounded process when it
tries to read input from its terminal. The typical response is to pause (as per
SIGSTOP and SIFTSTP) and wait for the SIGCONT that arrives when the
process is brought back to the foreground.
22 SIGTTOU The operating system sends this signal to a backgrounded process when it
tries to write output to its terminal. The typical response is as per
SIGTTIN.
23 SIGURG The operating system sends this signal to a process using a network
connection when “urgent” out of band data is sent to it.
24 SIGXCPU The operating system sends this signal to a process that has exceeded its
CPU limit. You can cancel any CPU limit with the shell command
“ulimit -t unlimited” prior to running make though it is more
likely that something has gone wrong if you reach the CPU limit in make.
25 SIGXFSZ The operating system sends this signal to a process that has tried to create a
file above the file size limit. You can cancel any file size limit with the
shell command “ulimit -f unlimited” prior to running make though it is
more likely that something has gone wrong if you reach the file size limit
in make.
26 SIGVTALRM This is very similar to SIGALRM, but while SIGALRM is sent after a
certain amount of real time has passed, SIGVTALRM is sent after a certain
amount of time has been spent running the process.
27 SIGPROF This is also very similar to SIGALRM and SIGVTALRM, but while
SIGALRM is sent after a certain amount of real time has passed, SIGPROF
is sent after a certain amount of time has been spent running the process
and running system code on behalf of the process.
28 SIGWINCH (Mostly unused these days.) A process used to be sent this signal when one
of its windows was resized.
29 SIGIO (Also known as SIGPOLL.) A process can arrange to have this signal sent
to it when there is some input ready for it to process or an output channel
has become ready for writing.
30 SIGPWR A signal sent to processes by a power management service to indicate that
power has switched to a short term emergency power supply. The process
(especially long-running daemons) may care to shut down cleanlt before
the emergency power fails.
31 SIGSYS Unused.


Courtesy: University of Cambridge

Unix well known port numbers

Port Number	Description
1	TCP Port Service Multiplexer (TCPMUX)
5	Remote Job Entry (RJE)
7	ECHO
18	Message Send Protocol (MSP)
20	FTP -- Data
21	FTP -- Control
22	SSH Remote Login Protocol
23	Telnet
25	Simple Mail Transfer Protocol (SMTP)
29	MSG ICP
37	Time
42	Host Name Server (Nameserv)
43	WhoIs
49	Login Host Protocol (Login)
53	Domain Name System (DNS)
69	Trivial File Transfer Protocol (TFTP)
70	Gopher Services
79	Finger
80	HTTP
103	X.400 Standard
108	SNA Gateway Access Server
109	POP2
110	POP3
115	Simple File Transfer Protocol (SFTP)
118	SQL Services
119	Newsgroup (NNTP)
137	NetBIOS Name Service
139	NetBIOS Datagram Service
143	Interim Mail Access Protocol (IMAP)
150	NetBIOS Session Service
156	SQL Server
161	SNMP
179	Border Gateway Protocol (BGP)
190	Gateway Access Control Protocol (GACP)
194	Internet Relay Chat (IRC)
197	Directory Location Service (DLS)
389	Lightweight Directory Access Protocol (LDAP)
396	Novell Netware over IP
443	HTTPS
444	Simple Network Paging Protocol (SNPP)
445	Microsoft-DS
458	Apple QuickTime
546	DHCP Client
547	DHCP Server
563	SNEWS
569	MSN
1080	Socks

HP UX Patch level

The patch level can be found by looking at the installed bundles. The bundles can be found by running the following command:

swlist -l bundle | grep -i patch

Compare the bundles.

There can also be several patches installed that are not in a bundle. These can be found by running the following command:

/usr/contrib/bin/show_patches

It is also possible to have installed patches that are not configured. You can check for these kinds of patches with the following command:

swlist -l patch -a state

Finding superblocks and fsck in RHEL

"If it looks like there is an issue with the filesystem's superblock. By running the command below we can check for the location of where backup superblocks will be:

mkfs.ext3 -n /dev/mapper/vg01-lvol5

The mkfs command may cause you some worry, but I'd like to stress the importance of -n option. This causes it to not actually perform any changes. Here is an excerpt from the mkfs.ext3 man page:

 -n     Causes mke2fs to not actually create a filesystem,  but  display

              what it would do if it were to create a filesystem.  This can be

              used to determine the location of the backup superblocks  for  a

              particular  filesystem,  so  long  as the mke2fs parameters that

              were passed when the filesystem was originally created are  used

              again.  (With the -n option added, of course!)

After this we can look for the lines simlar to:

Superblock backups stored on blocks:

    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Take the first value, i.e. 32768 and try using the commands I previously pasted with the -b option.

Once again confirm that the operation to be performed looks sane, keeping in mind to replace 32768 with your actual value:

fsck -b 32768 -fN /dev/mapper/vg01-lvol5

Then if it looks good try with:

fsck -b 32768 -fy /dev/mapper/vg01-lvol5

If you find the first backup superblock does not work try again with the next available one, i.e. 98304.

Again please make sure to have the filesystem unmounted."