Command Snips

For infrequent things I tend not to remember off the top of my head.

Shell

Linux Kernel CPU Reset

 echo 1 > /proc/sys/kernel/sysrq
 echo b > /proc/sysrq-trigger

tcpdump ipv6

 tcpdump -i <interface name> -n -vv ‘(udp port 546 or 547) or icmp6’

Date String Stamp

`date '+%Y-%m-%d-%Hh%M'`

• For Example:

mysqldump ... > bleh.`date '+%Y-%m-%d-%Hh%M'`.sql 
zfs snapshot -r tank@copec-snap_`date '+%Y-%m-%d-%Hh%M'`

Lock gnome >3.8 remote

DISPLAY=:0 dbus-send --type=method_call --dest=org.gnome.ScreenSaver /org/gnome/ScreenSaver org.gnome.ScreenSaver.Lock

Re-Mount / RW (I always forget the exact syntax...)

• Might want to add standard mount options to the "-o" like "discard" or "noatime"

mount -o remount,rw /

MySQL

Create New Database and User

For database 'new_db_name' and user 'new_user':

mysql --defaults-file=/etc/mysql/debian.cnf 
CREATE DATABASE new_db_name;
CREATE USER 'new_user'@'localhost' IDENTIFIED BY 'good_password';
CREATE USER 'new_user'@'%' IDENTIFIED BY 'good_password';
GRANT ALL PRIVILEGES ON new_db_name.* TO 'new_user'@'localhost';
GRANT ALL PRIVILEGES ON new_db_name.* TO 'new_user'@'%';
FLUSH PRIVILEGES;

Update User Password

SET PASSWORD FOR 'username'@'%.example.com' = PASSWORD('good_password');

Mysqlchecks

mysqlcheck --all-databases --repair
mysqlcheck --all-databases --optimize

Dumps

• For human consumption:

mysqldump --defaults-file=/etc/mysql/debian.cnf --skip-opt <databasename>

Binary Logs

• Purge all logs:

PURGE BINARY LOGS BEFORE now();

• Disable logging: /etc/mysql/conf.d/mysql_skip_log_bin.cnf:

[mysqld]
skip_log_bin

OpenSSL Testing

• https://easyengine.io/tutorials/mail/server/testing/smtp/

RAID

mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sda2 /dev/sdb2
mdadm --detail --scan >> /etc/mdadm/mdadm.conf

Mirror Website

wget --mirror --convert-links --adjust-extension --page-requisites --no-parent http://example.org

Systemd

• Flush DNS cache using the systemd stub resolver:

systemd-resolve --flush-caches
systemd-resolve --statistics

MacOS

• https://apple.stackexchange.com/questions/48502/how-can-i-permanently-add-my-ssh-private-key-to-keychain-so-it-is-automatically

Linux kexec reboot

alias kreboot="echo Loading kexec; kexec -l /vmlinuz --initrd=/initrd.img --reuse-cmdline; echo Rebooting; kexec -e"