====== Linux ======

**udev rules (for ASM) :**
<sxh bash>
ENV{DM_VG_NAME}=="oradisksASM" ENV{DM_LV_NAME}=="DISK*" OWNER="oracle" GROUP="dba"
</sxh>

**LVM :**
<sxh bash>
lvdisplay --noheadings --units m -C -o Size /dev/db2vg/lv_RAW01
</sxh>

**OpenSSL file encryption :**
<sxh bash>
openssl aes-256-cbc -a -salt -in secrets.txt -out secrets.txt.enc
</sxh>

**OpenSSL file decryption :**
<sxh bash>
openssl aes-256-cbc -d -a -in secrets.txt.enc -out secrets.txt.new
</sxh>

===== Cluster =====
**Install components [ALL NODES] :**
<sxh bash>
yum -y install pcs pacemaker fence-agents-all
</sxh>

**Set password of user hacluster [ALL NODES] :**
<sxh bash>
passwd hacluster
</sxh>

**Enable services [ALL NODES] :**
<sxh bash>
systemctl start pcsd.service
systemctl enable pcsd.service
</sxh>

**Create authentication tokens [FROM PRIM. NODE] :**
<sxh bash>
pcs cluster auth dbp04allx.unixguest.eu dbp26allx.unixguest.eu dbp05allx.unixguest.eu
</sxh>

**Create cluster [FROM PRIM. NODE] :**
<sxh bash>
pcs cluster setup --start --name HADR_ISM dbp04allx.unixguest.eu dbp26allx.unixguest.eu dbp05allx.unixguest.eu
</sxh>

**Enable cluster services on boot [FROM PRIM. NODE] :**
<sxh bash>
pcs cluster enable --all
</sxh>

=====List Services=====
You can list services in Linux as follows:

<Code:bash|List services>
[root@tain-cx-uatdb1 ~]# systemctl list-unit-files
UNIT FILE                                     STATE
proc-sys-fs-binfmt_misc.automount             static
dev-hugepages.mount                           static
dev-mqueue.mount                              static
proc-fs-nfsd.mount                            static
proc-sys-fs-binfmt_misc.mount                 static
sys-fs-fuse-connections.mount                 static
sys-kernel-config.mount                       static
sys-kernel-debug.mount                        static
tmp.mount                                     disabled
var-lib-nfs-rpc_pipefs.mount                  static
brandbot.path                                 enabled
systemd-ask-password-console.path             static
systemd-ask-password-plymouth.path            static
systemd-ask-password-wall.path                static
session-1.scope                               static
session-29975.scope                           static
session-29979.scope                           static
acpid.service                                 enabled
arp-ethers.service                            disabled
auditd.service                                enabled
auth-rpcgss-module.service                    static
autofs.service                                disabled
</Code>

====Check process connections====
We can check if a process is making connection from outside as follows:

<Code:bash|Check process connections>
[root@ag-se-tlcasdb1 ~]#  lsof -i -a -p 4970
COMMAND  PID   USER   FD   TYPE   DEVICE SIZE/OFF NODE NAME
oracle  4970 oracle   16u  IPv6 37827976      0t0  TCP ag-se-tlcasdb1.net.tain.com:ncube-lm->172.25.2.12:43612 (ESTABLISHED)
</Code>

As we can see, that is very useful for oracle processes. When the connection HAS to create process also ON the local server.