{"id":1945,"date":"2021-03-10T06:00:00","date_gmt":"2021-03-10T12:00:00","guid":{"rendered":"https:\/\/www.bigdatainrealworld.com\/?p=1945"},"modified":"2023-02-19T07:31:42","modified_gmt":"2023-02-19T13:31:42","slug":"what-does-hadoop-namenode-format-do-and-is-it-safe-to-run","status":"publish","type":"post","link":"https:\/\/www.bigdatainrealworld.com\/what-does-hadoop-namenode-format-do-and-is-it-safe-to-run\/","title":{"rendered":"What does hadoop namenode -format do and is it safe to run?"},"content":{"rendered":"\n<p>Don\u2019t run the command until you fully understand what you are trying to do.<\/p>\n\n\n\n<p><span style=\"font-weight: 400;\"><code>hadoop namenode -format<\/code> will format or delete all files and folders in the Namenode directory.<\/span><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span style=\"font-weight: 400;\">Namenode &amp; HDFS metadata<\/span><\/h2>\n\n\n\n<p><span style=\"font-weight: 400;\">Namenode is responsible for maintaining the metadata of HDFS. This includes information about the files, directories, block locations, permissions etc.<\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">The above information is maintained under directory specified by <code>dfs.namenode.name.dir<\/code><\/span><\/p>\n\n\n\n<pre class=\"wp-block-preformatted lang:default decode:true\">&lt;property>\u00a0\n   &lt;name>dfs.namenode.name.dir&lt;\/name>\u00a0\n   &lt;value>file:\/\/\/data\/dfs\/namenode&lt;\/value>\u00a0\n&lt;\/property><\/pre>\n\n\n\n<p><span style=\"font-weight: 400;\">hadoop namenode -format will wipe out the directory clean. This means you don\u2019t have a way to know what was in the HDFS because you have now essentially deleted all the metadata managed by NameNdoe even though the data that is managed by the DataNode will not be deleted.<\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">You usually don\u2019t perform this operation on a cluster that is in operation. It is usually performed on a failed installation where you have decided to start from scratch.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Don\u2019t run the command until you fully understand what you are trying to do. hadoop namenode -format will format or delete all files and folders in<span class=\"excerpt-hellip\"> [\u2026]<\/span><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28],"tags":[],"class_list":["post-1945","post","type-post","status-publish","format-standard","hentry","category-hdfs"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.7 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>What does hadoop namenode -format do and is it safe to run? - Big Data In Real World<\/title>\n<meta name=\"description\" content=\"Understand what would happen to your data stored in HDFS when you execute a format command on Hadoop&#039;s Namenode.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.bigdatainrealworld.com\/what-does-hadoop-namenode-format-do-and-is-it-safe-to-run\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What does hadoop namenode -format do and is it safe to run? 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