Tips & Tricks

Common #

Generate password #

$ openssl rand -base64 14
$ gpg --gen-random --armor 1 14
$ cat /dev/urandom | tr -dc a-zA-Z0-9 | fold -w 14 | head -n 1

Generate missed pub key from private #

$ ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub

Create a large file #

Linux & all filesystems

xfs_mkfile 10240m 10Gigfile

Linux & and some filesystems (ext4, xfs, btrfs and ocfs2)

fallocate -l 10G 10Gigfile

OS X, Solaris, SunOS and probably other UNIXes

mkfile 10240m 10Gigfile

Source

Date and time transformations #

# GNU date
timestamp -> human-readable
date -d @1339471282

human-readable -> timestamp
date --date="Tue 21 Jul 2020 03:56:50 PM MS" +"%s"

# BSD date
timestamp -> human-readable
date -r 1282368345

human-readable -> timestamp
date -j -f "%Y-%m-%d %H:%M:%S" "2018-01-30 15:58:50" "+%s"

MySQL #

Change user pass #

ALTER USER 'user'@'localhost' IDENTIFIED BY 'NEW_USER_PASSWORD';
FLUSH PRIVILEGES;

Granting User Connections From Remote Hosts: #

GRANT ALL PRIVILEGES ON *.* TO 'user'@'host' IDENTIFIED BY 'my-new-password' WITH GRANT OPTION;

PostgreSQL #

Create new user and DB #

sudo -u postgres createuser new-user
sudo -u postgres createdb new-db
sudo -u postgres psql

alter user new-user with encrypted password 'secret-pass';
grant all privileges on database new-db to new-user;

Git #

Empty commit #

git commit --allow-empty -m "Empty commit message"

Rename local branch #

git checkout ${TARGET_BRANCH}
git branch -m ${NEW_BEANCH_NAME}

Copy file from other branch #

git checkout ${SOURCE_BRANCH} /path/to/file

Tmux #

:setw synchronize-panes

Windows cmd #

reg - regestery managging tool

reg query HKEY_LOCAL_MACHINE  # shows all keys in selected branch

wevtutil - shows Windiows logs

wevtutil el  # shows all available logs
wevtutil qe ${LOG_NAME} # shows events from selected log

systeminfo - provides software and hardware information

WSL #

wsl -l -all                         # List of all available distros
wsl -s ${distro_name}               # Set a distro as default
wsl --unregister ${distro_name}     # Delete distro

K8S #

Merge multiple kubectl configs into a single file #

# Make a copy of your existing config
$ cp ~/.kube/config ~/.kube/config.bak
# Merge the two config files together into a new config file
$ KUBECONFIG=~/.kube/config:/path/to/new/config kubectl config view --flatten > /tmp/config
# Replace your old config with the new merged config
$ mv /tmp/config ~/.kube/config
# (optional) Delete the backup once you confirm everything worked ok
$ rm ~/.kube/config.bak