Before upgrading take a backup of your data
backup
Create full backup:
pgbackrest --stanza=<stanza_name> --type=full backup
Install the postgres version you want to upgrade to, in this case, I am
upgrading from 15 to 16, the current PGDATA is /db/15 and the new PGDATA will
be /db/16.
apt install postgresql-16
initdb
Initialize the new postgres data directory:
/usr/lib/postgresql/16/bin/pg_ctl initdb -D /db/16
pg_hba.conf
Update in both /db/15/pg_hba.conf and /db/16/pg_hba.conf to use trust instead of scram-sha-256 and comment al the host entries to temporally restrict remote connections:
local all all trust
# host all all 0.0.0.0/0 scram-sha-256
upgrade check
Check if the upgrade is possible:
/usr/lib/postgresql/16/bin/pg_upgrade \
--old-datadir=/db/15 \
--new-datadir=/db/16 \
--old-bindir=/usr/lib/postgresql/15/bin \
--new-bindir=/usr/lib/postgresql/16/bin \
--link --check
You need to run this command as the
postgresuser
The output can be something like:
Performing Consistency Checks on Old Live Server
------------------------------------------------
Checking cluster versions ok
Checking database user is the install user ok
Checking database connection settings ok
Checking for prepared transactions ok
Checking for system-defined composite types in user tables ok
Checking for reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for incompatible "aclitem" data type in user tables ok
Checking for presence of required libraries fatal
Your installation references loadable libraries that are missing from the
new installation. You can add these libraries to the new installation,
or remove the functions using them from the old installation. A list of
problem libraries is in the file:
/db/16/pg_upgrade_output.d/20250225T182200.708/loadable_libraries.txt
Failure, exiting
In this case, the upgrade is not possible because of missing libraries, you can
check the loadable_libraries.txt file to see which libraries are missing, in
this case the postgis-3 library is missing:
could not load library "$libdir/postgis-3": ERROR: could not access file "$libdir/postgis-3": No such file or directory
In database: test_dev1
In database: restore_test_dev1
It can happen that you end in a loop because when installing the new libraries
it will remove the old extensions in the ../15/lib, for this you can copy the
/usr/lib/postgresql/15/lib to /usr/lib/postgresql/15/lib.old:
cp -r /usr/lib/postgresql/15/lib /usr/lib/postgresql/15/lib.old
Do now the upgrade of the libraries for the new version, in this case, the
postgis-3 library and when finished move back the lib.old to lib:
mv /usr/lib/postgresql/15/lib.old /usr/lib/postgresql/15/lib
This is because depending on the OS the libraries will remove the old extensions
when installing the new ones, this can cause the pg_upgrade to fail.
After you have installed the new libraries you can run the pg_upgrade command again:
in RH based systems the libraries are in
/usr/pgsql-15/liband/usr/pgsql-16/librespectively, and may need to run:dnf upgrade --allowerasing *.rpmand thendnf install *.rpmin the directory containing the new libraries.
After fixing the missing libraries you can run the pg_upgrade command again
and output should be like:
Performing Consistency Checks on Old Live Server
------------------------------------------------
Checking cluster versions ok
Checking database user is the install user ok
Checking database connection settings ok
Checking for prepared transactions ok
Checking for system-defined composite types in user tables ok
Checking for reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for incompatible "aclitem" data type in user tables ok
Checking for presence of required libraries ok
Checking database user is the install user ok
Checking for prepared transactions ok
Checking for new cluster tablespace directories ok
*Clusters are compatible*
upgrade
Run the upgrade:
/usr/lib/postgresql/16/bin/pg_upgrade \
--old-datadir=/db/15 \
--new-datadir=/db/16 \
--old-bindir=/usr/lib/postgresql/15/bin \
--new-bindir=/usr/lib/postgresql/16/bin \
--old-options="-c config_file=/db/15/postgresql.conf" \
--new-options="-c config_file=/db/16/postgresql.conf"\
--link
you need to stop the old postgres server before running this command
systemctl stop postgresql-15
The output should be like:
Performing Consistency Checks
-----------------------------
Checking cluster versions ok
Checking database user is the install user ok
Checking database connection settings ok
Checking for prepared transactions ok
Checking for system-defined composite types in user tables ok
Checking for reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for incompatible "aclitem" data type in user tables ok
Creating dump of global objects ok
Creating dump of database schemas
ok
Checking for presence of required libraries ok
Checking database user is the install user ok
Checking for prepared transactions ok
Checking for new cluster tablespace directories ok
If pg_upgrade fails after this point, you must re-initdb the
new cluster before continuing.
Performing Upgrade
------------------
Setting locale and encoding for new cluster ok
Analyzing all rows in the new cluster ok
Freezing all rows in the new cluster ok
Deleting files from new pg_xact ok
Copying old pg_xact to new server ok
Setting oldest XID for new cluster ok
Setting next transaction ID and epoch for new cluster ok
Deleting files from new pg_multixact/offsets ok
Copying old pg_multixact/offsets to new server ok
Deleting files from new pg_multixact/members ok
Copying old pg_multixact/members to new server ok
Setting next multixact ID and offset for new cluster ok
Resetting WAL archives ok
Setting frozenxid and minmxid counters in new cluster ok
Restoring global objects in the new cluster ok
Restoring database schemas in the new cluster
ok
Adding ".old" suffix to old global/pg_control ok
If you want to start the old cluster, you will need to remove
the ".old" suffix from /db/15/global/pg_control.old.
Because "link" mode was used, the old cluster cannot be safely
started once the new cluster has been started.
Linking user relation files
ok
Setting next OID for new cluster ok
Sync data directory to disk ok
Creating script to delete old cluster ok
Checking for extension updates notice
Your installation contains extensions that should be updated
with the ALTER EXTENSION command. The file
update_extensions.sql
when executed by psql by the database superuser will update
these extensions.
Upgrade Complete
----------------
Optimizer statistics are not transferred by pg_upgrade.
Once you start the new server, consider running:
/usr/lib/postgresql/16/bin/vacuumdb --all --analyze-in-stages
Running this script will delete the old cluster's data files:
./delete_old_cluster.sh
timed out waiting for input: auto-logout
disable old
Disable the old postgres version:
systemctl disable postgresql-15.service
verify PGDATA
Verify the new PGDATA is correct, check with:
systemctl cat postgresql-16.service
Ensure the Environment variable is set to the new PGDATA:
Environment=PGDATA=/db/16
start new
Start the new postgres version:
systemctl start postgresql-16.service
Run the vacuumdb command to update the optimizer statistics:
/usr/lib/postgresql/16/bin/vacuumdb --all --analyze-in-stages