Add a key for an apt repo

apt-key adv --keyserver keyserver.ubuntu.com --recv-keys xxxxxx

Configure a local postfix to relay mail to gmail

Add to /etc/postfix/main.cf

    relayhost = smtp.gmail.com:587
    smtp_sasl_auth_enable = yes
    smtp_sasl_password_maps=hash:/etc/postfix/sasl_passwd
    smtp_sasl_security_options = noanonymous
    smtp_use_tls = yes

Create /etc/postfix/sasl_passwd and run 'postmap /etc/postfix/sasl_passwd'

    smtp.gmail.com:587 [email protected]:password

/etc/posfix/virtual

All mail that goes to @relay-mailer gets sent to the gmail user

    @relay-mailer [email protected]

Configure a central rsyslog server

1. Configure an rsyslog client to send its syslog to the server.
2. Configure an rsyslog server to accept remote logs and log each host's logs into its own log file.

Client:

On the client side, edit /etc/rsyslog.d/50-default.conf and enter the following at the bottom of the file (use your syslog server's ip address):

    *.* @1.2.3.4:514

Then restart rsyslog: systemctl restart rsyslog

Server:

On the syslog server, toward the top of /etc/rsyslog.conf, enter the following two lines:

module(load="imudp") input(type="imudp" port="514" ruleset="RemoteLogs")

You may uncomment the lines that are there regarding udp module/input. The important part is to tie this input to a ruleset named RemoteLogs.

Create a file: /etc/rsyslog.d/49-RemoteLogs.conf with the following contents:

    ruleset(name="RemoteLogs"){
        $template RemoteLogsTemplate,"/var/log/remote/%HOSTNAME%.log"
        *.* ?RemoteLogsTemplate
    }

The directory /var/log/remote/ must be owned by syslog:adm and writable.

mkdir -p /var/log/remote

chown syslog:adm /var/log/remote

Then, restart rsyslog: systemctl restart rsyslog

Verifying that a Certificate is issued by a CA

How to use OpenSSL on the command line to verify that a certificate was issued by a specific CA, given that CA's certificate

$ openssl verify -verbose -CAfile cacert.pem server.crt server.crt: OK If you get any other message, the certificate was not issued by that CA.

Test Authenticated Squid SSL Proxy with Curl

• marshall@basement:~$ http_proxy='http://tester:[email protected]:3128'
• marshall@basement:~$ https_proxy='http://tester:[email protected]:3128'
• marshall@basement:~$ curl -v -I https://www.google.com

Convert NetApp Volume Serial to NAA

lun serial -x /vol/test/lun

Serial (hex)#: 0x486e542d4f5a2f47694d684b

Take the example of a LUN with the following NAA number:

naa.60a98000486e542d4f5a2f47694d684b

Log into an ISCSI Target

iscsiadm --mode discovery -t sendtargets --portal

iscsiadm --mode node --targetname --portal --login

Create the Unit/Service /usr/lib/systemd/system/myservice.service file with the following content:

[Unit]
Description=A service that does something

[Service]
Type=simple
ExecStart=/my/path/myservice.sh

[Install]
WantedBy=multi-user.target

Create the /usr/lib/systemd/system/myservice.timer file with the following content:

[Unit]
Description=Execute backup every day at midnight

[Timer]
OnCalendar=*-*-* 00:00:00
Unit=myservice.service

[Install]
WantedBy=multi-user.target

Enable and start the timer service:

chmod ugo+x /my/path/myservice.sh
systemctl enable myservice.timer
systemctl start myservice.timer

Install grub to a second disk drive

If you are trying to make a copy of an entire system like /dev/sda to /dev/sdb, these are the steps you may run afterward to install grub to the new disk and also copy the mbr from one disk to the other.

dd if=/dev/sda of=/dev/sdb bs=512 count=1
mount --bind /dev /mnt/dev 
mount --bind /proc /mnt/proc 
mount --bind /sys /mnt/sys
cd /mnt
chroot .
update-grub2
grub-install /dev/sdb

show remaining life of eMMC

RES=`cat /sys/kernel/debug/mmc1/mmc1:0001/ext_csd`
typea="${RES:536:2}" ;
typeb="${RES:538:2}" ;
typead=`echo "ibase=16; $typea"|bc`
typebd=`echo "ibase=16; $typeb"|bc`
echo "Type A percent: $((typead * 10)) %"
echo "Type B percent: $((typebd * 10)) %"

Check temperature of Cat 1k Cisco switch

Cisco1k24>show env temperature status
System Temperature Value: 62 Degree Celsius
PHY Temperature Value: 55 Degree Celsius
DDR Temperature Value: 58 Degree Celsius
System Temperature State: GREEN
Yellow Threshold : 85 Degree Celsius
Red Threshold    : 88 Degree Celsius

Check MySQL Memory Settings

#!/bin/sh
# you might want to add some user authentication here
mysql -u root -p  -e "show variables; show status" | awk '
{
VAR[$1]=$2
}
END {
MAX_CONN = VAR["max_connections"]
MAX_USED_CONN = VAR["Max_used_connections"]
BASE_MEM=VAR["key_buffer_size"] + VAR["query_cache_size"] + VAR["innodb_buffer_pool_size"] + VAR["innodb_additional_mem_pool_size"] + VAR["innodb_log_buffer_size"]
MEM_PER_CONN=VAR["read_buffer_size"] + VAR["read_rnd_buffer_size"] + VAR["sort_buffer_size"] + VAR["join_buffer_size"] + VAR["binlog_cache_size"] + VAR["thread_stack"] + VAR["tmp_table_size"]
MEM_TOTAL_MIN=BASE_MEM + MEM_PER_CONN*MAX_USED_CONN
MEM_TOTAL_MAX=BASE_MEM + MEM_PER_CONN*MAX_CONN
printf "+------------------------------------------+--------------------+\n"
printf "| %40s | %15.3f MB |\n", "key_buffer_size", VAR["key_buffer_size"]/1048576
printf "| %40s | %15.3f MB |\n", "query_cache_size", VAR["query_cache_size"]/1048576
printf "| %40s | %15.3f MB |\n", "innodb_buffer_pool_size", VAR["innodb_buffer_pool_size"]/1048576
printf "| %40s | %15.3f MB |\n", "innodb_additional_mem_pool_size", VAR["innodb_additional_mem_pool_size"]/1048576
printf "| %40s | %15.3f MB |\n", "innodb_log_buffer_size", VAR["innodb_log_buffer_size"]/1048576
printf "+------------------------------------------+--------------------+\n"
printf "| %40s | %15.3f MB |\n", "BASE MEMORY", BASE_MEM/1048576
printf "+------------------------------------------+--------------------+\n"
printf "| %40s | %15.3f MB |\n", "sort_buffer_size", VAR["sort_buffer_size"]/1048576
printf "| %40s | %15.3f MB |\n", "read_buffer_size", VAR["read_buffer_size"]/1048576
printf "| %40s | %15.3f MB |\n", "read_rnd_buffer_size", VAR["read_rnd_buffer_size"]/1048576
printf "| %40s | %15.3f MB |\n", "join_buffer_size", VAR["join_buffer_size"]/1048576
printf "| %40s | %15.3f MB |\n", "thread_stack", VAR["thread_stack"]/1048576
printf "| %40s | %15.3f MB |\n", "binlog_cache_size", VAR["binlog_cache_size"]/1048576
printf "| %40s | %15.3f MB |\n", "tmp_table_size", VAR["tmp_table_size"]/1048576
printf "+------------------------------------------+--------------------+\n"
printf "| %40s | %15.3f MB |\n", "MEMORY PER CONNECTION", MEM_PER_CONN/1048576
printf "+------------------------------------------+--------------------+\n"
printf "| %40s | %18d |\n", "Max_used_connections", MAX_USED_CONN
printf "| %40s | %18d |\n", "max_connections", MAX_CONN
printf "+------------------------------------------+--------------------+\n"
printf "| %40s | %15.3f MB |\n", "TOTAL (MIN)", MEM_TOTAL_MIN/1048576
printf "| %40s | %15.3f MB |\n", "TOTAL (MAX)", MEM_TOTAL_MAX/1048576
printf "+------------------------------------------+--------------------+\n"
}'

Clean Old Data from Zabbix Database

time mysql zabbix -e "
RENAME TABLE history_uint TO history_uint_old;
CREATE TABLE history_uint LIKE history_uint_old;
SET SESSION SQL_LOG_BIN=0;
INSERT INTO history_uint (
SELECT * FROM history_uint_old WHERE clock >= UNIX_TIMESTAMP(
\"$(date +%Y-%m-%d) 00:00:00\"
)
);
DROP TABLE history_uint_old;
"

time mysql zabbix -e "
RENAME TABLE history_str TO history_str_old;
CREATE TABLE history_str LIKE history_str_old;
SET SESSION SQL_LOG_BIN=0;
INSERT INTO history_str (
SELECT * FROM history_str_old WHERE clock >= UNIX_TIMESTAMP(
\"$(date +%Y-%m-%d) 00:00:00\"
)
);
DROP TABLE history_str_old;
"

time mysql zabbix -e "
RENAME TABLE history_log TO history_log_old;
CREATE TABLE history_log LIKE history_log_old;
SET SESSION SQL_LOG_BIN=0;
INSERT INTO history_log (
SELECT * FROM history_log_old WHERE clock >= UNIX_TIMESTAMP(
\"$(date +%Y-%m-%d) 00:00:00\"
)
);
DROP TABLE history_log_old;
"

time mysql zabbix -e "
RENAME TABLE history_text TO history_text_old;
CREATE TABLE history_text LIKE history_text_old;
SET SESSION SQL_LOG_BIN=0;
INSERT INTO history_text (
SELECT * FROM history_text_old WHERE clock >= UNIX_TIMESTAMP(
\"$(date +%Y-%m-%d) 00:00:00\"
)
);
DROP TABLE history_text_old;
"

time mysql zabbix -e "
RENAME TABLE history TO history_old;
CREATE TABLE history LIKE history_old;
SET SESSION SQL_LOG_BIN=0;
INSERT INTO history (
SELECT * FROM history_old WHERE clock >= UNIX_TIMESTAMP(
\"$(date +%Y-%m-%d) 00:00:00\"
)
);
DROP TABLE history_old;
"

time mysql zabbix -e "
RENAME TABLE trends_uint TO trends_uint_old;
CREATE TABLE trends_uint LIKE trends_uint_old;
SET SESSION SQL_LOG_BIN=0;
INSERT INTO trends_uint (
SELECT * FROM trends_uint_old WHERE clock >= UNIX_TIMESTAMP(
\"$(date +%Y-%m-%d) 00:00:00\"
)
);
DROP TABLE trends_uint_old;
"

time mysql zabbix -e "
RENAME TABLE trends TO trends_old;
CREATE TABLE trends LIKE trends_old;
SET SESSION SQL_LOG_BIN=0;
INSERT INTO trends (
SELECT * FROM trends_old WHERE clock >= UNIX_TIMESTAMP(
\"$(date +%Y-%m-%d) 00:00:00\"
)
);
DROP TABLE trends_old;
"

Reclaim space on a VMware vmdk disk

Log into the virtual machine and run the following command:
dd if=/dev/zero of=/mounted-volume/zeroes && rm -f /mounted-volume/zeroes

Power off the virtual machine

Log into esx CLI and navigate into the virtual machine's directory in /vmfs/volumes/.../

Run the command:
vmkfstools -K disk_name.vmdk using the name of your vmdk disk. Not the -flat.vmdk.