File & Directory

Published on: 22nd Apr 2014

Updated on: 12th Jan 2023

File & director operations

Jump to my home directory,
```
cd ~/
```
To create directory,
```
mkdir my_new_directory
```
To remove directory including the sub-directories,
```
rm -r my_directory
```
To edit a text file,
```
nano filename
```
Or if the file requires root permission,
```
sudo nano filename
```
To copy file/directory,
```
cp from_file to_file
```
To rename or move file/directory,
```
mv old_name new_name
```

File & directory permissions

To change user's home directory,

sudo usermod -d /home/newdirectory -m ftpuser

To change a directory or file permission (where '777' is full access to everyone - refers to the Reference section in this topic).
```
chmod 777 my_directory
```
Or using sudo if root permission is required
```
sudo chmod 777 my_directory
```
chmod manages file and directory from three different user perspective aside from the access right, where
- 'Owner' is the first number (7 in this case).
- 'Group' is the second number (7 in this case).
- 'Others' (or anyone else) is the third number (7 in this case).
And each flag has three types of access right or action,
- Read (value of 4)
- Write (value of 2)
- Execute (value of 1)
- where
  - 7 is full access (i.e., the sum of 1 + 2 + 4).
  - 0 means no access at all.
Notes: if you have a bash file (with .sh file extension) that does not have execute access right, then, you will not be able to execute that bash file.
We use chown command to change the directory/file owner to current user,
```
sudo chown -R $(whoami) my_directory
```
Or change the owner to 'tester' (an user ID),
```
sudo chown -R tester my_directory
```
Or change the owner to 'tester' and group ('officeusers'),
```
sudo chown -R tester:officeusers my_directory
```

Quota

22.Sep.2022: Enable the storage quota for the user,

If the user is allowed in accessing the server storage, you may want to limit their usage by setting a quota for them.
```
sudo apt update
sudo apt install quota
```
To confirm that the quota feature has been installed, run this:
```
quota --version
```

Make sure that the quota module is in the OS.

find  /lib/modules/ -type f -name '*quota_v*'

In my virtual machine, I have this result,

/lib/modules/5.4.0-65-generic/kernel/fs/quota/quota_v2.ko
/lib/modules/5.4.0-65-generic/kernel/fs/quota/quota_v1.ko
/lib/modules/5.4.0-97-generic/kernel/fs/quota/quota_v2.ko
/lib/modules/5.4.0-97-generic/kernel/fs/quota/quota_v1.ko

In case the file does not exist, try this:

sudo apt install linux-image-extra-virtual

This is for AWS server,

sudo apt install linux-modules-extra-aws

Edit the file system configuration,
```
sudo nano /etc/fstab
```
Replaced the 'defaults' word with 'usrquota,grpquota'.
```
UUID=c474e3a1-a40f-4a66-becf-1fa084f95832 / ext4 usrquota,grpquota 0 0
```
Notes: you may have different UUID value and it is ok.
After that, we will have to remount the file system with the following command,
```
sudo mount -o remount /
```
To verify the changes, run the following command.
```
cat /proc/mounts | grep ' / '
```
I see the following result.
```
/dev/sda2 / ext4 rw,relatime,quota,usrquota,grpquota 0 0
```
Notes: you may have different value of '/dev/sda2' and it is ok.

Now, we are ready to turn on the quota module,

sudo quotacheck -ugm /

Where 'u' is user, 'g' is group and 'm' is no remount.

For more information about the paramters, please refers to https://manpages.ubuntu.com/manpages/bionic/man8/quotacheck.8.html

This generates 2 files (aquota.group and aquota.user):

tester@ubuntu11:~$ ls -la /
total 132
drwxr-xr-x  23 root root  4096 Sep 22 10:36 ./
drwxr-xr-x  23 root root  4096 Sep 22 10:36 ../
-rw-------   1 root root 10240 Sep 22 10:36 aquota.group
-rw-------   1 root root  8192 Sep 22 10:36 aquota.user
drwxr-xr-x   2 root root 12288 Feb  3  2022 bin/
drwxr-xr-x   3 root root  4096 Feb  3  2022 boot/
...

Reboot the server. This is to ensure that the server is able to start normally after the above changes.
Finally, you may set the quota for the user. In the following example, I'll allocate 1GB storage space to myftpuserid account.
```
sudo setquota -u myftpuserid 1G 1.2G 0 0 /
```
Notes: the first 1G is the soft limit and then the 1.2G is the hard limit. The last two zero is to limit by the number of files.
In case you want to review the quota usage, run the following commands.
```
sudo repquota -s /
```

References

For more details about chmod command:

https://ss64.com/bash/chmod.html
For more details about chown command:

https://ss64.com/bash/chown.html
How To Set Filesystem Quotas on Ubuntu 20.04:

https://www.digitalocean.com/community/tutorials/how-to-set-filesystem-quotas-on-ubuntu-20-04
11.Aug.2024 - fixing disk space issue in Linux

https://docs.digitalocean.com/support/how-do-i-fix-disk-space-issues-on-my-droplet/

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Author

Lau Hon Wan, software developer.