Author: paul.deluca

How do I manage core dumps on Linux?

To aid in troubleshooting, core dumps are sometimes enabled. A core dump file is the memory image of an executable program when it was terminated by the operating system due to various error behavior. Whenever a process is killed, a core.PID file will be created in the working directory.

If you are concerned about filesystem space, you may remove these files at any time.

If you would like to disable core dumps entirely, modify /etc/profile to contain the following line:

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

If you wish to re-enable core dumps, change the same line to read:

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

If you want to check the status of core dumps, use the ulimit command:

[root@eclipse ~]# ulimit -a
core file size (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 1064960
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 1064960
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

How do I maximize a hidden Solar window stuck on the toolbar?

If a Solar window refuses to maximize, it may be hidden off the screen or behind the toolbar. To find the window, right-click on the toolbar  icon for the window you’re trying to maximize – select “move” in the menu.

Use the arrow keys (start by holding the up arrow key) to see if the window comes into view.  Once you see it, you may have to resize it by grabbing the lower corner and dragging it open.

If none of the arrow keys bring the window into view, you may need to completely un-install and re-install Solar.  http://kb.eclipseinc.com/kb/how-do-i-clear-the-java-cache-to-reinstall-solar/

Contact Eclipse Systems if you need assist.

How do I prevent my Seagate USB drive from powering down?

Seagate manufactures a number of low-cost USB hard drives that are popular with our customers. While these drives will certainly work for backup purposes, their unique power-saving features are known to cause issue with Linux systems. By default, the drives will power down after a period of inactivity to save power, and when they’re accessed again, they often come back as read-only filesystems. Unmounting and remounting the drive returns the drive to read-write mode, but there is a simple, long-term workaround to avoid this solution entirely.

To change the drive’s power saving setting, the drive must be disconnected from the Linux server and plugged into a Windows server or workstation with Seagate Dashboard installed.

Open Seagate Dashboard
Select the drive you wish to adjust by choosing it in the dropdown menu. If only one Seagate drive is available, it will be preselected.
Click Drive Settings in the Drives panel.
The Drive Settings window opens. Click Power Settings.
Select the “Never” interval from the dropdown menu.
Click Save to save the Drive Sleep Interval setting.
The Power Settings window confirms that the power setting for your drive has been changed.
Click Close to return to the Seagate Dashboard window.

For more information, please see Seagate’s KB entry on the subject.

The Eclipse Systems team continues to recommend RDX-based storage solutions, such as the Dell RD1000, for customers who wish to purchase certified and supported storage devices purpose-built for reliable backups.

How do I update a Linux user’s home directory?

For more information on the new home directory format, please see this advisory.
Before making changes to your system, please review the general system administration best practices.

To migrate existing Linux users’ home directories to the new format:

Verify that /u2/eclipse/.profile has been updated:

vi /u2/eclipse/.profile

The following block of code must appear before “Setup the Eclipse environment.” If it doesn’t, add it:

# Move to the Eclipse account home directory
export ECLIPSEHOME=/u2/eclipse
cd $ECLIPSEHOME

After the .profile has been updated, backup the existing /etc/passwd file containing user information:

TIMESTAMP=`date +%Y%m%d.%H%M%S`
echo "`date`: backing up /etc/passwd to /etc/passwd.$TIMESTAMP"
cp /etc/passwd /etc/passwd.$TIMESTAMP

Run the following script to update the existing user’s home directories:

ECLIPSEHOME=/u2/eclipse
echo "`date`: started user migration"
awk -F":" '{ print $1 " " $6 }' /etc/passwd | egrep "$ECLIPSEHOME$" | sort | {
    while read LINE; do
        USERNAME=$(echo $LINE | awk '{print $1}')
        ECLIPSEHOME=$(echo $LINE | awk '{print $2}')
        echo "`date`: Setting $USERNAME's home directory to /home/$USERNAME with a link to $ECLIPSEHOME/.profile"
        mkdir -p /home/$USERNAME
        chown $USERNAME /home/$USERNAME
        usermod -d /home/$USERNAME $USERNAME
        ln -sf $ECLIPSEHOME/.profile /home/$USERNAME/.profile
        ln -sf $ECLIPSEHOME/.profile /home/$USERNAME/.bash_profile
    done
}

Log in as an Eterm user to verify that the steps been completed properly. If you encounter any issues, please open a support request.

Review the updated user maintenance procedures.

 

Can I safely ignore I/O errors on dm devices?

The root user of a system using may occasionally receive a message similar to the following in the daily logwatch email:

--------------------- Kernel Begin ------------------------

WARNING:  Kernel Errors Present
    Buffer I/O error on device dm-7,  ...:  11 Time(s)
    EXT3-fs error (device dm-7): e ...:  90 Time(s)
    lost page write due to I/O error on dm-7 ...:  11 Time(s)

Likewise, you may notice similar error messages in the /var/log/messages file:

May 16 04:04:52 eclipse kernel: lost page write due to I/O error on dm-20       
May 16 04:04:52 eclipse kernel: Buffer I/O error on device dm-20, logical block 0
May 16 04:04:52 eclipse kernel: lost page write due to I/O error on dm-20       
May 16 04:04:52 eclipse kernel: Buffer I/O error on device dm-20, logical block 0
May 16 04:04:52 eclipse kernel: lost page write due to I/O error on dm-20       
May 16 04:04:52 eclipse kernel: Buffer I/O error on device dm-20, logical block 0
May 16 04:04:52 eclipse kernel: lost page write due to I/O error on dm-20

If the device mapper (dm-n) device(s) mentioned in the messages refer to a snapshot logical volume (LV), these messages can be ignored. By their definition, snapshot LVs are temporal in nature; they are created, destroyed and expire when changes written to them exceed their predefined capacity.

To determine if the dm device points to a snapshot LV:

First, locate the “dm” device number in the logs (in our example, 20):

[root@eclipse ~]# grep "I/O error" /var/log/messages
May 16 04:04:52 eclipse kernel: Buffer I/O error on device dm-20, logical block 1545
May 16 04:04:52 eclipse kernel: lost page write due to I/O error on dm-20

Next, list the /dev/mapper/* devices, noting the minor device numbers of each, which correspond with the “dm” device number (in our example, 20):

[root@eclipse ~]# ls -l /dev/mapper/ | grep 20
brw-rw---- 1 root disk 253, 20 May 16 14:00 datavg-lvol1

Finally, list the LVs in the noted volume group to determine whether or not it’s a snapshot, signified by the “s” in Attr column and presence of Origin and Snap% values:

[root@eclipse ~]# lvs datavg
  LV       VG     Attr   LSize   Origin   Snap%  Move Log Copy%  Convert
  eclipse  datavg owi-ao 395.00G                                        
  ereports datavg owi-ao   1.00G                                        
  lvol0    datavg swi-ao   1.00G u2         0.41                        
  lvol1    datavg swi-ao  34.82G eclipse    0.74                        
  lvol2    datavg swi-ao   1.00G ereports   0.00                        
  lvol3    datavg swi-ao   3.61G pdw        0.01                        
  pdw      datavg owi-ao  45.00G                                        
  u2       datavg owi-ao   4.00G                                        
  uvtmp    datavg -wi-ao   4.00G

In our example, the Origin LV is /dev/datavg/eclipse, and the dm-20 device referenced in the error messages is indeed a snapshot LV.

If the dm-n device(s) mentioned in the messages do not refer to a snapshot logical volume (LV), you may have a filesystem, software or hardware issue, and you should contact your Red Hat support provider.