System Dump [AIX]

1. What is dump?
2. Configuring dump devices in AIX
3. How to start the system dump manually?
4. Copying system dump to other directory or media
5. Examining system dump using kdb
6. Important LED codes related to dump

If a kernel panic occurs, a dump will be invoked automatically. The followings are dumped during the dump process.

1. List of currently running processes and related information about the process
2. Currently mounted filesystems, inode table and open file table
3. currently configured ttys and their status
4. Memory buffers for data
5. system buffers
6. system variables and statistics
7. Kernel's own record of process it is currently running.

Configuring dump devices

sysdumpdev command is used to change the primary or secondary dump device designation in a running system.

 sysdumpdev 
           -l list the current dump destination
           -L view statistical information about previous dump
           -e estimate the dump size
           -d <directory> directory to copy the dump during boot time
           -p <device name>  to set the device as primary dump device
           -s <device name> to set the device as secondary dump device
           -P to make the changes permanent even after reboot

Examples:

To permanently make /dev/hd7 as the primary dump device

 # sysdumpdev -Pp /dev/hd7

To make /dev/sysdumpnull as the secondary dump device

 # sysdumpdev -s /dev/sysdumpnull

To estimate the dump size

 #susdumpdev -e

To start the dump manually

sysdumpstart command is used to start a kernel dump to the primary or secondary dump device. When the dump completes, the system halts. Use the kdb command to examine the dump.

 # sysdumpstart {-p | -s}

Copying system dump

If there is enough space to copy the dump to /var/adm/ras directory, then it will be copied directly during reboot. Dump is copied as /var/adm/ras/vmcore.x file. If there is not enough space, then "copydumpmenu" is run by /sbin/rc.boot to display the copy dump menu. Using this copydumpmenu utility, a dump can be copied to removable such as tape.

snap

 utility can be used to gather system information along with dump and compress the information in a tar file.

snap

    -a  gathers all system configuration information
    -c  creates compressed pax image (snap.pax.Z)
    -e  HACMP specific information
    -g  gathers general info
    -f  gathers filesystem info
    -k  gathers kernel info
    -d <directory> optional snap command output directory
       default directory is /tmp/ibmsupt
    -D  gathers dump and /unix
    -o <output_device>  copies the compressed image to tape or diskette

Example:

To send dump with other gathered information in to tape drive

 # snap -gfkD -o /dev/rmt0

  Examining system dump

kdb command is an interactive utility for examining an OS image or the running kernel.

 kdb <systemImageFile [Kernel File]]

LED Codes Related to dump

 0c0 - Dump completed successfully
 0c2 - Dump started
 0c4 - Dump unsuccessful. Not enough space on dump device
 0c5 - Dump failed to start
 0c9 - System initiated dump started