Hadoop security Mode

SafeMode mode
Namenode first enters Safe mode when booting, if Datanode lost block reaches a certain proportion (1-dfs.safemode.threshold.pct), then the system will always be in Safe mode state is read-only state.
dfs.safemode.threshold.pct (default 0.999f) indicates when HDFs is started, if the number of blocks escalated by Datanode reaches the meta  0.999 times times the number of blocks in the data record can leave Safe mode, otherwise this is always read-only mode. If set to 1, HDFs is always in safemode.
The following line extracts the log from the Namenode startup (block escalation ratio 1 to the threshold 0.9990)
The ratio of reported blocks 1.0000 has reached the threshold 0.9990. Safe mode is turned off automatically in seconds.
Hadoop Dfsadmin-safemode Leave
There are two ways to get out of this safe mode
1. Modify the dfs.safemode.threshold.pct to a relatively small value, the default is 0.999.
2. Hadoop dfsadmin-safemode leave command forced to leave
Http://bbs.hadoopor.com/viewthread.php?tid=61&extra=page%3D1

Hadoop security Mode