Hadoop release "Name node is in safe mode"

Source: Internet
Author: User

The resolved command:

Hadoop dfsadmin-safemode leave #关闭safe 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 that when HDFs starts, it is always this read-only mode if the number of blocks reported by Datanode reaches 0.999 times times the block number of the metadata record to leave safe 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



Safe mode is exited when the minimal replication condition are reached, plus an extension

Time of seconds. The minimal replication condition is while 99.9% of the blocks in

The whole filesystem meet their minimum replication level (which defaults to one, and

is set by Dfs.replication.min).

Security Mode exit premise-The minimum backup level is reached for the blocks of the entire file system (99.9% by default, which can be set by dfs.safemode.threshold.pct) (default is 1, Can be set via Dfs.replication.min).

dfs.safemode.threshold.pct float 0.999

The proportion of blocks in the system that must meet the minimum

Replication level defined by Dfs.rep Lication.min before the Namenode

would exit Safe mode. Setting

This value is 0 or less forces the Name-node not to start in safe mode.

Setting this value to more than 1 means the namenode never exits safe



The user can operate the Safe mode by Dfsadmin-safemode value, the parameter value is described as follows:

Enter-Enter Safe mode

Leave-Force Namenode to leave Safe mode

Get-Returns information about whether Safe mode is turned on

Wait-waits until the end of safe mode.

Hadoop release "Name node is in safe mode"

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.