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os_cp:users_permissions [2023/04/02 11:10] jkonczak utworzono |
os_cp:users_permissions [2024/03/19 15:54] (current) jkonczak [Users and groups] |
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A user is identified by a numerical __u__ser __id__entifier – **uid**. Uids are mapped to usernames. | A user is identified by a numerical __u__ser __id__entifier – **uid**. Uids are mapped to usernames. | ||
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- | A group is identified by a numerical __g__roup __id__entifier – **uid**, that are likewise mapped to group names. | + | A group is identified by a numerical __g__roup __id__entifier – **gid**, that are likewise mapped to group names. |
A user must be in one primary group and can be in multiple supplementary groups. | A user must be in one primary group and can be in multiple supplementary groups. | ||
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<html></small></html> | <html></small></html> | ||
- | The user whose uid equals **0** is referred to as **superuser**. Traditional username of the superuser is **[[https://pl.wikipedia.org/wiki/Root|root]]**. | + | The user whose uid equals **0** is referred to as **superuser**. Traditional username of the superuser is **[[https://en.wikipedia.org/wiki/Superuser|root]]**. |
To check who you are, you can run the ''**whoami**'' command. \\ | To check who you are, you can run the ''**whoami**'' command. \\ | ||
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<small>Additionally, there are three other special permissions: set-user-id (suid, __**s**__), set-group-id (sgid, __**s**__) and sticky (__**t**__).</small> | <small>Additionally, there are three other special permissions: set-user-id (suid, __**s**__), set-group-id (sgid, __**s**__) and sticky (__**t**__).</small> | ||
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+ | Upon file access, when the file belongs to the current user, only user's permissions are considered.\\ | ||
+ | If the file does not belong to the user but the user belongs to the file's group, only group's permissions are considered.\\ | ||
+ | If the file does not belong to the user and the user does not belong to the file's group, only others' permission are considered.\\ | ||
+ | <small>Note that if a file has read permission for the group but no read permission for the user, then the owner cannot display the file even if the owner belongs to the file's group.</small> | ||
The execute mode for files stands for running them (e.g., as a program or a script), for directories – entering it. | The execute mode for files stands for running them (e.g., as a program or a script), for directories – entering it. |