After upgrading PostgreSQL from version 9.2 to 9.3 on Ubuntu, many users encounter the frustrating version mismatch error when trying to use pg_dump:

pg_dump: server version: 9.3.4; pg_dump version: 9.2.8
pg_dump: aborting because of server version mismatch

The problem occurs because the pg_dump command is actually a symlink to /usr/share/postgresql-common/pg_wrapper, which maintains multiple PostgreSQL versions. During the upgrade, the system might not automatically update the default version used by the wrapper.

First, check what PostgreSQL versions you have installed:

ls -l /usr/lib/postgresql/

And verify where your pg_dump points to:

which pg_dump
ls -l $(which pg_dump)

The most reliable fix is to ensure all PostgreSQL client tools are upgraded:

sudo apt-get update
sudo apt-get install postgresql-client-9.3 postgresql-common

You can directly call the version-specific pg_dump:

/usr/lib/postgresql/9.3/bin/pg_dump -U username dbname > backup.sql

To avoid similar problems during future upgrades:

sudo update-alternatives --config pg_dump

Select the appropriate version from the list presented.

If issues persist, check the complete environment:

echo $PATH
pg_dump --version
psql --version

Remember that server and client versions must match for certain operations.

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So you've successfully upgraded PostgreSQL from 9.2 to 9.3 following the official Ubuntu repository instructions, but now pg_dump is throwing this frustrating error:

pg_dump: server version: 9.3.4; pg_dump version: 9.2.8
pg_dump: aborting because of server version mismatch

The issue stems from Ubuntu's postgresql-common package maintaining version-specific binaries in separate paths. The pg_dump command is actually a wrapper script (/usr/share/postgresql-common/pg_wrapper) that tries to find the correct version, but sometimes gets confused after upgrades.

First, let's verify which versions are actually installed:

dpkg -l | grep postgresql-9.

And check where the binaries are located:

ls -l /usr/lib/postgresql/*/bin/pg_dump

Here's how to properly resolve this:

sudo apt-get update
sudo apt-get install --reinstall postgresql-client-9.3 postgresql-common

After running these commands, verify the fix:

pg_dump --version

If the above doesn't work, try specifying the full path to the 9.3 version:

/usr/lib/postgresql/9.3/bin/pg_dump -U username dbname > backup.sql

Or create an alias in your .bashrc:

alias pg_dump='/usr/lib/postgresql/9.3/bin/pg_dump'

When upgrading PostgreSQL in the future, always remember to:

• First stop all PostgreSQL services
• Explicitly install the new version's client tools
• Remove old versions completely if not needed

For systems with multiple PostgreSQL versions, you can configure the default version:

sudo update-alternatives --config pg_dump

Select the appropriate version from the list presented.