Month: November 2021

Postgres DB migration error due to replication

We got a weird error today when running the latest migration on a production Postgres DB.

cannot update table "schema_info" because it does not have a replica identity and publishes updates

The table schema_info is created when we run ruby Sequel migrations. This table stores just the version number of the latest migration applied under a column called version.

We had set up a replica database some time ago and it looked like the issue was because of this.

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Disable specific default Windows key shortcuts

A number of times, I prefer to use the Windows key on the keyboard to create shortcuts, especially to applications which I use frequently.

However, Windows has a default set of keyboard shortcuts that it maps to various applications and those key mappings can’t be changed. A few examples are Cortana (Win+C), Clipboard (Win+V).

To get around this, the Registry Editor needs to be modified.

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users and sudo in Linux

Every time I need to create, modify, grant sudo access to users in Linux, I have to search for it.

This is a list of the commands I’ve used in the past.

Will keep updating this so that I don’t have to load a search page every time!

All commands below are run as root user. If I’m not the root user, I need to prefix them with sudo!

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Postgres authentication

Reference: Stackoverflow

pg_hba.conf controls the authentication method. If you want to request a password, use md5 authentication. If you want to allow login with no password to anyone, use trust. If you want to require the same username in the operating system as in PostgreSQL, use peer (UNIX, only for local connections) or sspi (Windows).

If there’s a password set, but pg_hba.conf doesn’t tell PostgreSQL to ask for it, the password is ignored.

If pg_hba.conf tells PostgreSQL to ask for a password but there’s none set, then all login attempts will fail no matter what password is supplied.

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