Linux permissions
The shared folders
The BiRD platform manages the shared folders under the directories:
- /LAB-DATA/BiRD/shares/<folder>
- /SCRATCH-BIRD/shares/<folder>
These folders are accessible upon request for each user with the agreement of the project manager.
Description of files and folder permissions
The files and folder permissions are managed by the owner of these files and folders. A linux file or folder always has an owner and a group. Use the "ls" command with "-l" argument to visualize the linux rights:
(base) [charpentier-e1@login-01 results]$ ls -lh
total 17G
-rw-rw---- 1 charpentier-e1 dge-seq 17G 3 mars 2020 2015_10_06_DGESeqrun1MiSeq.zip
drwxrws--- 1 charpentier-e1 dge-seq 4 23 août 2018 analyseBIRD_RUN10_human_solenne
drwxrws--- 1 charpentier-e1 dge-seq 4 23 août 2018 analyseBIRD_RUN11_human_solenne
Triplets of permissions are set for the owner, the group, and others:
- the first letter is the type of file: "d" for directory, "-" for file
- the first triplet are the permissions for the user (owner)
- the second triplet are the permissions for the group
- the third triplet are the permissions for the rest of the users of the server
The letter code for the triplets are
- "r" for read
- "w" for write
- "x" or "s" for execute
Changing file permissions
These permissions can be changed with the "chmod" command
Octal representation
| Octal Digit | Binary Representation (rwx) | Permission |
|---|---|---|
| 4 | 100 | read only |
| 5 | 101 | read and execute |
| 6 | 110 | read and write |
| 7 | 111 | read, write, and execute (full permissions) |
User categories
| symbol | category | Description |
|---|---|---|
| u | user | Owner of the file |
| g | group | Group of the file |
| o | other | All other users of the server |
Using the chmod command
# set write permission for the group
chmod g+w <file>
# remove write permission for the group
chmod g-w <file>
# set read/write/execute for the user, read/execute permission for the group, and none for others
chmod 750 <folder>
# set read/write/execute permissions recursively for user and group
chmod -R 770 <folder>
Most commonly used commands to set permissions on folder and all subfolders/files
# find all sub-folders inside a folder and set read/write/execute for user and group
find <folder> -type d -exec chmod 770 {} \;
# find all files inside a folder recursively and set read/write for user and group
find <folder> -type f -exec chmod 660 {} \;Notes
- Replace <folder> or <file> with the real path of the folder/file you want to change permissions on.
- Only the owner of the file/folder can change its permissions.
- "x" permission on a folder is necessary to enter the directory (i.e., cd into it), and to access any of its files.
Links
Linux permission tutorial (french): https://linux.goffinet.org/administration/securite-locale/permissions-linux/
Linux permission tutorial (english): https://www.digitalocean.com/community/tutorials/an-introduction-to-linux-permissions
SO question on recursive permissions changing: https://stackoverflow.com/questions/19737525/find-type-f-exec-chmod-644
Ubuntu documentation for permissions: https://doc.ubuntu-fr.org/permissions