diff --git a/beacon_chain/beacon_chain_db.nim b/beacon_chain/beacon_chain_db.nim
index f2add63a7..b16983b5d 100644
--- a/beacon_chain/beacon_chain_db.nim
+++ b/beacon_chain/beacon_chain_db.nim
@@ -1082,16 +1082,18 @@ iterator getAncestorSummaries*(db: BeaconChainDB, root: Eth2Digest):
     # from the old format, this brings down the write from minutes to seconds
     stmt.dispose()
 
-    if newSummaries.len() > 0:
-      db.withManyWrites:
-        for s in newSummaries:
-          db.putBeaconBlockSummary(s.root, s.summary)
+    if not db.db.readOnly:
+      if newSummaries.len() > 0:
+        db.withManyWrites:
+          for s in newSummaries:
+            db.putBeaconBlockSummary(s.root, s.summary)
+
+      # Clean up pre-altair summaries - by now, we will have moved them to the
+      # new table
+      db.db.exec(
+        "DELETE FROM kvstore WHERE key >= ? and key < ?",
+        ([byte ord(kHashToBlockSummary)], [byte ord(kHashToBlockSummary) + 1])).expectDb()
 
-    # Clean up pre-altair summaries - by now, we will have moved them to the
-    # new table
-    db.db.exec(
-      "DELETE FROM kvstore WHERE key >= ? and key < ?",
-      ([byte ord(kHashToBlockSummary)], [byte ord(kHashToBlockSummary) + 1])).expectDb()
   var row: stmt.Result
   for rowRes in exec(stmt, root.data, row):
     expectDb rowRes
diff --git a/ncli/ncli_db.nim b/ncli/ncli_db.nim
index b0b10f376..0889bef74 100644
--- a/ncli/ncli_db.nim
+++ b/ncli/ncli_db.nim
@@ -132,9 +132,9 @@ type
         defaultValue: 0
         desc: "The era number to write".}: uint64
       eraCount* {.
-        defaultValue: 1
+        defaultValue: 0
         name: "count"
-        desc: "Number of eras to write".}: uint64
+        desc: "Number of eras to write (0=all)".}: uint64
 
     of DbCmd.importEra:
       eraFiles* {.
@@ -314,7 +314,7 @@ proc cmdBench(conf: DbConf, cfg: RuntimeConfig) =
   printTimers(false, timers)
 
 proc cmdDumpState(conf: DbConf) =
-  let db = BeaconChainDB.new(conf.databaseDir.string)
+  let db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer: db.close()
 
   let
@@ -352,7 +352,7 @@ proc cmdPutState(conf: DbConf, cfg: RuntimeConfig) =
       db.putState(state)
 
 proc cmdDumpBlock(conf: DbConf) =
-  let db = BeaconChainDB.new(conf.databaseDir.string)
+  let db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer: db.close()
 
   for blockRoot in conf.blockRootx:
@@ -391,7 +391,7 @@ proc cmdPutBlock(conf: DbConf, cfg: RuntimeConfig) =
 
 proc cmdRewindState(conf: DbConf, cfg: RuntimeConfig) =
   echo "Opening database..."
-  let db = BeaconChainDB.new(conf.databaseDir.string)
+  let db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer: db.close()
 
   if (let v = ChainDAGRef.isInitialized(db); v.isErr()):
@@ -422,7 +422,7 @@ func atCanonicalSlot(blck: BlockRef, slot: Slot): BlockSlot =
     blck.atSlot(slot - 1).blck.atSlot(slot)
 
 proc cmdExportEra(conf: DbConf, cfg: RuntimeConfig) =
-  let db = BeaconChainDB.new(conf.databaseDir.string)
+  let db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer: db.close()
 
   if (let v = ChainDAGRef.isInitialized(db); v.isErr()):
@@ -443,7 +443,8 @@ proc cmdExportEra(conf: DbConf, cfg: RuntimeConfig) =
     tmp: seq[byte]
     timers: array[Timers, RunningStat]
 
-  for era in conf.era ..< conf.era + conf.eraCount:
+  var era = conf.era
+  while conf.eraCount == 0 or era < conf.era + conf.eraCount:
     if shouldShutDown: quit QuitSuccess
     let
       firstSlot =
@@ -457,24 +458,29 @@ proc cmdExportEra(conf: DbConf, cfg: RuntimeConfig) =
       break
 
     let name = withState(dag.headState.data): eraFileName(cfg, state.data, era)
-    echo "Writing ", name
+    if isFile(name):
+      echo "Skipping ", name, " (already exists)"
+    else:
+      echo "Writing ", name
 
-    let e2 = openFile(name, {OpenFlags.Write, OpenFlags.Create}).get()
-    defer: discard closeFile(e2)
+      let e2 = openFile(name, {OpenFlags.Write, OpenFlags.Create}).get()
+      defer: discard closeFile(e2)
 
-    var group = EraGroup.init(e2, firstSlot).get()
-    if firstSlot.isSome():
-      withTimer(timers[tBlocks]):
-        var blocks: array[SLOTS_PER_HISTORICAL_ROOT.int, BlockId]
-        for i in dag.getBlockRange(firstSlot.get(), 1, blocks)..<blocks.len:
-          if dag.getBlockSSZ(blocks[i], tmp):
-            group.update(e2, blocks[i].slot, tmp).get()
+      var group = EraGroup.init(e2, firstSlot).get()
+      if firstSlot.isSome():
+        withTimer(timers[tBlocks]):
+          var blocks: array[SLOTS_PER_HISTORICAL_ROOT.int, BlockId]
+          for i in dag.getBlockRange(firstSlot.get(), 1, blocks)..<blocks.len:
+            if dag.getBlockSSZ(blocks[i], tmp):
+              group.update(e2, blocks[i].slot, tmp).get()
 
-    withTimer(timers[tState]):
-      dag.withUpdatedState(tmpState[], canonical) do:
-        withState(stateData.data):
-          group.finish(e2, state.data).get()
-      do: raiseAssert "withUpdatedState failed"
+      withTimer(timers[tState]):
+        dag.withUpdatedState(tmpState[], canonical) do:
+          withState(stateData.data):
+            group.finish(e2, state.data).get()
+        do: raiseAssert "withUpdatedState failed"
+
+    era += 1
 
   printTimers(true, timers)
 
@@ -494,6 +500,8 @@ proc cmdImportEra(conf: DbConf, cfg: RuntimeConfig) =
 
   var data: seq[byte]
   for file in conf.eraFiles:
+    if shouldShutDown: quit QuitSuccess
+
     let f = openFile(file, {OpenFlags.Read}).valueOr:
       warn "Can't open ", file
       continue
@@ -550,7 +558,7 @@ type
 proc cmdValidatorPerf(conf: DbConf, cfg: RuntimeConfig) =
   echo "Opening database..."
   let
-    db = BeaconChainDB.new(conf.databaseDir.string,)
+    db = BeaconChainDB.new(conf.databaseDir.string, readOnly = true)
   defer:
     db.close()