File Systems

Types of file systems

• Windows:

  • Installation FS:

    • FAT (File Allocation Table);

    • NTFS (New Technology File System);

  • Native recognized FS:

    • FAT;

    • NTFS;

    • ExFAT (Extended File Allocation Table);

• Linux:

  • Installation FS:

    • Ext (Extended File System);

    • ReiserFS;

    • ...

  • Native recognized FS: almost all;

Quota

• Limit on disk usage (inodes or blocks);

• Can be set on a per-user or per-group basis;

• Max number of files is related to the limit on inodes (1 file = 1 inode);

• Max disk space is related to the limit on blocks;

• Hard limit: user cannot exceed the limit;

• Soft limit: user can exceed the limit for a certain amount of time (grace period) before the hard limit is enforced;

Quota Packages

Package	Description
quota	user and group quotas
quota-tools	project quotas

• Mount options:

  • usrquota: user quotas;

  • grpquota: group quotas;

  • prjquota: project quotas;

• Quota configuration files are located at partition root:

  • /aquota.user: user quotas;

  • /aquota.group: group quotas;

  • /aquota.project: project quotas;

Getting started with quotas

1. Install quota and quota-tools packages:

• Debian/Ubuntu:

sudo apt install quota quota-tools

• Arch/Manjaro:

sudo pacman -S quota quota-tools

1. In /etc/fstab, add usrquota and/or grpquota to the partition you want to enable quotas:

/dev/sda1 / ext4 defaults,usrquota,grpquota 0 1

1. Remount the partition:

sudo mount -o remount /

1. Create quota files:

sudo quotacheck -cug /

Disk management

Devices information

blkid

• List block devices connected to the system with:

  • UUID;

  • File system type;

  • Label if any;

  • System name.

• Filter by file system type with -t option:

sudo blkid -t TYPE=ext4

Extended access rights

SUID & SGID

• Set User/Group ID;

• Special permissions that can be set on executable files.

Sticky bit

• Special permission that can be set on directories;

• Prevents users from deleting files they do not own in a directory;

• View sticky bit with ls -l. You should see a t at the end of the permissions:

drwxrwxrwt  2 root root  4096 May  1 12:34 tmp

Find files

locate

• Fast;

• Searches in a database containing all files on the system;

• Does not search in real time, since the database needs to be updated first (updatedb command).

find

• Slower;

• Searches in real time.

• Can execute commands on the found files with -exec option;

find /home –size +100M –exec rm '{ }' ';'

• Can search by:

  • Name (-name);

  • Type;

  • Size (-size, -empty);

  • Permissions;

  • User (-user);

  • Group;

  • Date (-mtime, -daystart);

  • Content;

  • And more....

find / -name "file.txt"

which

Locates the default executable file associated with a command.

whereis

• Locates the executable file associated with a command;

• Locates the manual page associated with a command;

• Locates the source code associated with a command.