Enabling core dumps v16

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You can use core dumps to diagnose or debug errors. A core dump is a file containing a process's address space (memory) when the process terminates unexpectedly. Core dumps can be produced on demand, such as by a debugger, or upon termination.

Enabling core dumps on a RHEL or CentOS or Rocky Linux or AlmaLinux host

On RHEL/CentOS 7.x or RHEL/Rocky Linux/AlmaLinux 8.x, core file creation is disabled by default. To enable the core file generation:

Identify the system's current limit using the ulimit -c or ulimit -a command. 0 indicates that core file generation is disabled.

# ulimit -c
0

# 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) 3756
max locked memory       (kbytes, -l) 64
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) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 3756
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

Create a directory to store the core dumps, and modify kernel.core_pattern to store the dumps in a specified directory:

mkdir -p /var/coredumps
chmod a+w /var/coredumps

sysctl kernel.core_pattern=/var/coredumps/core-%e-%p
kernel.core_pattern = /var/coredumps/core-%e-%p

Persist the kernel.core_pattern setting across reboots:

echo 'kernel.core_pattern=/var/coredumps/core-%e-%p' >> /etc/sysctl.conf

Enable core dumps in /etc/security/limits.conf to allow a user to create core files. Each line describes a limit for a user in the following form:
```
<domain>  <type>  <item>  <value>
   *       soft    core    unlimited
```
Use * to enable the core dump size to unlimited.
Set the limit of core file size to UNLIMITED:
```
ulimit -c unlimited

ulimit -c
unlimited
```
To set a core limit for the services, add the following setting in /usr/lib/systemd/system/edb-as-15.service:
```
[Service]
LimitCore=Infinity
```
Reload the service configuration:
```
systemctl daemon-reload
```
Modify the global default limit using systemd. Add the following setting in /etc/systemd/system.conf:
```
DefaultLimitCORE=Infinity
```
Restart systemd:
```
systemctl daemon-reexec
```
Stop and then start EDB Postgres Advanced Server:
```
systemctl stop edb-as-15
systemctl start edb-as-15
```

Now, the core dumps are enabled. Install the gdb tool and debug packages:

yum install gdb
debuginfo-install edb-as15 edb-as15-server-contrib edb-as15-server edb-as15-libs

Replace the path to a core dump file. Then, get a backtrace using the bt command to analyze output:
```
gdb /usr/edb/as15/bin /var/coredumps/core-edb-postgres-65499
(gdb) bt full
```

Enabling core dumps on a Debian or Ubuntu host

On Debian 10 or Ubuntu 18 and 20, core file creation is disabled by default. To enable the core file generation:

Identify the system's current limit using the ulimit -c or ulimit -a command. 0 indicates that core file generation is disabled.

# ulimit -c
0

# 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) 7617
max locked memory       (kbytes, -l) 65536
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) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 7617
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

Create a new directory to store the core dumps, and modify kernel.core_pattern to store the dumps in a specified directory:

mkdir -p /var/coredumps
chmod a+w /var/coredumps

sysctl kernel.core_pattern=/var/coredumps/core-%e-%p
kernel.core_pattern = /var/coredumps/core-%e-%p

Persist the kernel.core_pattern setting across reboots:

echo 'kernel.core_pattern=/var/coredumps/core-%e-%p' >> /etc/sysctl.conf

To allow a user to create core files, enable core dumps in /etc/security/limits.conf. Each line describes a limit for a user in the following form.
```
<domain>  <type>  <item>  <value>
   *       soft    core    unlimited
```
Use * to enable the core dump size to unlimited.
Set the limit of core file size to UNLIMITED:
```
ulimit -c unlimited

ulimit -c
unlimited
```
To set a core limit for the services, add the following setting in /lib/systemd/system/edb-as@.service:
```
[Service]
LimitCore=Infinity
```
Reload the service configuration:
```
systemctl daemon-reload
```
Modify the global default limit using systemd. Add the following setting in /etc/systemd/system.conf:
```
DefaultLimitCORE=Infinity
```
Restart systemd:
```
systemctl daemon-reexec
```

Stop and then start EDB Postgres Advanced Server:

systemctl stop edb-as@15.service
systemctl start edb-as@15.service

Now, the core dumps are enabled. Install the gdb tool and debug symbols:

apt-get install gdb
apt-get install edb-as15 edb-as-contrib edb-as15-server edb-debugger-dbgsym

Replace the path to a core dump file. Then get a backtrace using the bt command to analyze output:
```
gdb /usr/lib/edb-as/15/bin /var/coredumps/core-edb-postgres-21638
(gdb) bt full
```

Note

The debug info packages name on a Debian or Ubuntu host can vary and include a -dbgsym or -dbg suffix. For more information about setting sources.list and installing the debug info packages, see the Debian wiki or the Ubuntu wiki.
The core files can be huge, depending on the memory usage. Enabling the core dumps on a system might fill up its mass storage over time.

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