# Upgrade to Smilo 2.6.0

Smilo 2.6.0 upgrades the base geth version from 1.8.18 to 1.9.7 See ethereum 1.9.0 for the complete list if new features added as a part of geth 1.9.7.

Note geth 1.9.7 has several enhancements at the database layer which are part of Smilo 2.6.0. Hence, once migrates to 2.6.0, it cannot rollback to older version of Quourm. The recommendation is to keep the back of the data directory before upgrading to 2.6.0 which can be used to revert back to older version if necessary.

A node running on Smilo 2.6.0 can coexist on a network where other nodes are running on lower version of Smilo and thus supports node by node upgrade to Smilo 2.6.0. The suggested upgrade process is as described below:

• Bring down the node which needs to be upgraded to Smilo 2.6.0. Modify the genesis.json file to include istanbulBlock and petersburgBlock. The values for this should be set to an appropriate value in future by when the entire network would have upgraded to Smilo 2.6.0. This is important as the gas calculation logic has changed in geth 1.9.7. Not setting this value properly can result in Bad block error
• Execute geth --datadir path/to/datadir init genesis.json with the modified genesis.json
• Bring up the node in Smilo 2.6.0

↳ !!! Note

• freezerdb - geth 1.9.7 brings in the feature of freezer db where in block data beyond certain threshold is moved to a different file based storage area. The location for freezerdb can be provided by geth command lines arguments as shown below:

--datadir.ancient value             Data directory for ancient chain segments (default = inside chaindata)

• When a node is migrated to this version, geth by default will create the ancient data folder and start moving blocks below the immutability threshold (default: 3162240) into the ancient data. If you do not want this movement to happen, use --immutabilitythreshold to set the immutability threshold to an appropriate value while bringing up geth

• geth 1.9.7 by default does not allow keystore based accounts to be unlocked in the start up process. geth will crash if the unlock is attempted as a part of start up. To enable account unlocking explicitly use --allow-insecure-unlock

--allow-insecure-unlock             Allow insecure account unlocking when account-related RPCs are exposed by http