{"id":6897,"date":"2021-06-09T13:18:40","date_gmt":"2021-06-09T13:18:40","guid":{"rendered":"https:\/\/linuxways.net\/?p=6897"},"modified":"2021-06-09T13:18:40","modified_gmt":"2021-06-09T13:18:40","slug":"chmod-command-in-linux","status":"publish","type":"post","link":"https:\/\/linuxways.net\/de\/ubuntu\/chmod-command-in-linux\/","title":{"rendered":"Chmod Command in Linux"},"content":{"rendered":"

The change of mode or chmod command lets you change the access mode of files in Linux. This lets you decide who can access and run files. We will be using chmod to change the permissions of files and directories in Ubuntu 20.04.<\/p>\n

To view the permissions for a file, use:<\/p>\n

ls \u2013l<\/pre>\n
<\/p>\n
What does all this mean?<\/p>\n
The first character identifies if it\u2019s a file (-) or a directory (d).<\/p>\n
Next is the permissions. The first three characters show the owner\u2019s permissions, the next three the group\u2019s permissions, and the last three others\u2019 permission. The table below explains the user types.<\/p>\n\n\n\n\n\n\n
User<\/strong><\/td>\nDescription<\/strong><\/td>\n<\/tr>\n
Owner<\/td>\nthis is the user who owns the file<\/td>\n<\/tr>\n
Group<\/td>\nthese are users who are part of a user group<\/td>\n<\/tr>\n
Others<\/td>\nthese are users other than the owner and group members<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Let\u2019s look at the user permissions in Linux. There are three basic permissions; read (r), write (w), and execute (x). Read means the user can only read or view the file. Write allows users to edit or delete a file. Execute allows users to execute the file. As you can see in the image above, the permissions are either represented as characters or -. The \u201c\u2013\u201c (dash) means the users don\u2019t have permission.<\/p>\n
The syntax of chmod is:<\/p>\n
chmod {users}{operator}{permission} {filename}<\/p>\n
Operators let you specify the permissions. We have three operators:<\/p>\n
+: Adds the permission<\/p>\n
-: Removes the permission<\/p>\n
=: Lets you specify the exact permission<\/p>\n
chmod has two modes, the symbolic and numeric modes. We will cover both.<\/p>\n
Symbolic Mode<\/h2>\n
Let\u2019s look at the file \u201chello.c\u201d. The user has all three permissions.<\/p>\n
<\/p>\n
If we want to change the permissions so that only the owner can read and write the file, while the group and others have read permission, we will use:<\/p>\n
chmod u=rw,og=r hello.c<\/pre>\n
<\/p>\n
To check if the permissions updated, use,<\/p>\n
ls \u2013l {filename}<\/pre>\n
<\/p>\n
If you want to add the execute permission for the owner, we use:<\/p>\n
chmod u+x hello.c<\/pre>\n
<\/p>\n
If we view the permissions now, we can see the execute permission for the owner.<\/p>\n
<\/p>\n
If we want to set the execute permission for all, we use:<\/p>\n
chmod a+x hello.c<\/pre>\n
<\/p>\n
If we view the permissions now, we can see the execute permission for all users.<\/p>\n
<\/p>\n
Numeric Mode<\/h2>\n
You can use a three-digit number to give permissions using chmod. Here is how it works, the leftmost digit represents the permission for the owner, the middle one is for group members, and the rightmost is for others.<\/p>\n
The permissions are as follows:<\/p>\n
Read = 4<\/p>\n
Write = 2<\/p>\n
Execute = 1<\/p>\n
No permissions = 0<\/p>\n
The table below summarizes the permissions.<\/p>\n\n\n\n\n\n\n\n\n\n\n
7<\/td>\nAll permissions<\/td>\n4+2+1<\/td>\n<\/tr>\n
6<\/td>\nRead and write<\/td>\n4+2+0<\/td>\n<\/tr>\n
5<\/td>\nRead and execute<\/td>\n4+0+1<\/td>\n<\/tr>\n
4<\/td>\nRead only<\/td>\n4+0+0<\/td>\n<\/tr>\n
3<\/td>\nWrite and execute<\/td>\n0+2+1<\/td>\n<\/tr>\n
2<\/td>\nWrite only<\/td>\n0+2+0<\/td>\n<\/tr>\n
1<\/td>\nExecute only<\/td>\n0+0+1<\/td>\n<\/tr>\n
0<\/td>\nNo permission<\/td>\n0+0+0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Let\u2019s use this method to set permission for ABC.txt.<\/p>\n
<\/p>\n
If we want the owner to have all permissions and group and others to have read permissions, we will use:<\/p>\n
chmod 744 ABC.txt<\/pre>\n
<\/p>\n
To check if the permissions updated, use,<\/p>\n
<\/p>\n
If you want to recursively change the permissions of all the files within a directory, use:<\/p>\n
chmod \u2013R {permissions} {filename}<\/pre>\n
<\/p>\n
This command gives the owner all three permissions and groups and others no permissions.<\/p>\n
<\/p>\n
If you want to know more about chmod, use:<\/p>\n
man chmod<\/pre>\n
<\/p>\n
This will take you to the manual that has all the details on this command.<\/p>\n
<\/p>\n
We covered both the symbolic and numeric mode of the chmod command in this article.<\/p>","protected":false},"excerpt":{"rendered":"
The change of mode or chmod command lets you change the access mode of files in Linux. This lets you decide who can access and run files. We…<\/p>","protected":false},"author":1,"featured_media":7095,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[360,100],"class_list":["post-6897","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ubuntu","tag-chmod-command","tag-ubuntu-20-04"],"_links":{"self":[{"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/posts\/6897","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/comments?post=6897"}],"version-history":[{"count":0,"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/posts\/6897\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/media\/7095"}],"wp:attachment":[{"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/media?parent=6897"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/categories?post=6897"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/linuxways.net\/de\/wp-json\/wp\/v2\/tags?post=6897"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}