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How do I enable core dumps on Red Hat Enterprise Linux?

A core dump is a on disk representation of a state of a user space application at the time of its abnormal termination. Core dumps can be used to diagnose the cause of a crash of an application.

Core dumps are not useful to end users, as they require specialised skills to analyze and determine the cause of the crash. In most cases, enabling a core dump is not necessary until there is a specific need.

In Red Hat Enterprise Linux, core file creation is disabled for interactive shells. This is configured in the /etc/profile by theulimit command.

The /etc/profile contains system wide environment variables and commands that will be run for any interactive shell. By default, it contains this line:

ulimit -S -c 0 > /dev/null 2>1

To enable core dumps for interactive or non-daemon programs, change this line to:

ulimit -S -c unlimited  >/dev/null 2>1

This will allow all users to produce core files with no upper size limit.

Resources:

Why are there so many J2EE phantoms running?

The connection pool of J2EE phantoms is automatically sized based on the number of UV licenses you have available on your server. The default setting is sized based on the number of connections that works best for a Solar customer.

If you are not a full Solar customer, or if do not wish to open as many connections, you may manually set the minimum and maximum number of connection pool J2EE phantoms.

The connection pool parameters are stored in $ACCOUNT_HOME/modules-conf/solar-jca.properties:

# The following settings control the size of the connection pool (min & max).
#
# If you don't specify a min or a max, the connection pool is automatically
# sized based on the number of UV licenses for the server.  This is good because
# we don't have to remember to change this file as the customer grows.  However,
# you probably want to restrict the connection pool size by setting the min and
# max for training/play accounts.
#
# The default for the min is 15% of the UV licenses.  The default for the max
# is the number of UV licenses - 5 (-5 if they have WOE) (-5 if they have
# BC:XML).  For example, 100 UV licenses and no companions: max of 95.  100 UV
# licenses and BC:XML: max of 90.

If you wish to change these parameters, the syntax is as follows:

pool.maxTotal=25
pool.minTotal=10

You must restart JBoss for the new settings to take effect.

How do I reset my Linux server’s root password?

Reset Root Password

If a root password is forgotten, you can reset it:

  • Reboot the server
  • From the grub boot menu, select the kernel
  • Press the e key to edit the entry
  • Select second line (the line starting with the word kernel)
  • Press the e key to edit kernel entry so that you can append single user mode
  • Append the letter S (or word Single) to the end of the (kernel) line
  • Press ENTER key
  • Now press the b key to boot the Linux kernel into single user mode
  • You may need to mount at least / and other partitions:
mount -t proc proc /proc
mount -o remount,rw /
  • Change the root password, enter:
passwd

Finally reboot system:

sync
reboot

How do I stop and start Eclipse services on Linux?

Stop Eclipse

  • Stop VSIFAX:
vfxsched stop
  • Stop samba:
service smb stop
  • Stop PostgreSQL:
service postgresql-8.4 stop

RHEL7

systemctl stop postgresql-9.5
  • Stop SYSTEM.ADMIN, phantoms, JBoss:
service monit stop
service eclipse-jboss stop
service eclipse-system-admin stop

RHEL7

systemctl stop eclipse-api-release
systemctl stop eclipse-jboss.service 
systemctl stop eclipse-system-admin.service
For secondary accounts (play, train, stage, etc.), substitute “eclipse” for the account name. For example, a “train” account services would be referred to as train-jboss and train-system-admin.
  • Stop UV processes:
cd /u2/uv
bin/uv
#ESC
MASTER OFF ALL
Q
  • Stop remaining phantoms, UV processes:
ps -ef|grep phantom|awk '{print $2}'|xargs -i kill -4 {}
  • Stop UV:
service uv.rc stop

RHEL7

systemctl stop  universe
  • If UV complains that there are open processes, check:
lsof /u2
ipcs -mop|grep 0xaceb

Start Eclipse

  • Start UV:
service uv.rc start

RHEL7

systemctl start  universe
  • Start PostgreSQL:
service postgresql-8.4 start

RHEL7

systemctl start postgresql-9.5
  • Start SYSTEM.ADMIN, phantoms, JBoss:
service monit start
service eclipse-system-admin start
service eclipse-jboss start

RHEL7

systemctl start eclipse-system-admin.service 
systemctl start eclipse-jboss.service 
systemctl start eclipse-api-release
For secondary accounts (play, train, stage, etc.), substitute “eclipse” for the account name. For example, a “train” account services would be referred to as train-jboss and train-system-admin.
  • Start samba:
service smb start

RHEL7

systemctl start smb
  • Start VSIFAX:
vfxsched start