Disk quota and sysd procd
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This document discusses disk quotas, procfs, sysfs, and process information on Linux systems. It provides information on setting up and using disk quotas, describes the purpose and structure of the procfs and sysfs filesystems, and lists various files and directories that can be found under procfs for obtaining system and process information. Instructions are given on installing and configuring disk quotas, and examples of files that can be found under procfs and sysfs are provided.
![Gaurav Mishra <gmishx@gmail.com>
Disk Quota
To use disk quota on a Linux system, you need to follow these steps.
1. Install quota
a) sudo apt-get install quota
2. Inform system about quota
a) Edit /etc/fstab
a) Append defaults,[usrquota][,grpqouta] 1 1
3. Remount the disk
a) mount -o remount /home
4. Create the quota database
a) quotacheck -c<u/g> filesystem
5. Assign the quotas
a) Assign per user or per group quotas
a) edquota -<u/g>
28-02-2018](https://image.slidesharecdn.com/linux-8-180304061238/85/Disk-quota-and-sysd-procd-3-320.jpg)
![Gaurav Mishra <gmishx@gmail.com>
Disk Quota tools
• quotacheck
▫ It scan a filesystem for disk usage, create, check and repair quota files.
▫ Creating new quota database for a partition
quotacheck -c<u/g> /dev/sda1
• edquota
▫ It access and modify user quota on a quota database for a partition
▫ Creating limit for a user
edquota [-ugpt] optimus
• quotaon
▫ Turn file system quota ON.
• quotaoff
▫ Turn file system quota OFF.
• repqouta
▫ Prints a summary of the disc usage and quotas for the specified file systems
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Disk quota and sysd procd
- 1. Gaurav Mishra <[email protected]> Linux - 8 Disk Quota, sys and proc directory Unrestricted 28-02-2018
- 2. Gaurav Mishra <[email protected]> Disk Quota • Disk quota helps in setting disk usage limits/caps on users/groups in Linux environment. • The free space on disk is a shared resource and can be used by any user. • It is helpful in shared environments to restrict users consuming all of the space. • Disk quota are applied on a file system on a disk partition. • It can be soft or hard limit. 28-02-2018
- 3. Gaurav Mishra <[email protected]> Disk Quota To use disk quota on a Linux system, you need to follow these steps. 1. Install quota a) sudo apt-get install quota 2. Inform system about quota a) Edit /etc/fstab a) Append defaults,[usrquota][,grpqouta] 1 1 3. Remount the disk a) mount -o remount /home 4. Create the quota database a) quotacheck -c<u/g> filesystem 5. Assign the quotas a) Assign per user or per group quotas a) edquota -<u/g> 28-02-2018
- 4. Gaurav Mishra <[email protected]> Disk Quota tools • quotacheck ▫ It scan a filesystem for disk usage, create, check and repair quota files. ▫ Creating new quota database for a partition quotacheck -c<u/g> /dev/sda1 • edquota ▫ It access and modify user quota on a quota database for a partition ▫ Creating limit for a user edquota [-ugpt] optimus • quotaon ▫ Turn file system quota ON. • quotaoff ▫ Turn file system quota OFF. • repqouta ▫ Prints a summary of the disc usage and quotas for the specified file systems 28-02-2018
- 5. Gaurav Mishra <[email protected]> PROCFS • The proc filesystem (procfs) is a special filesystem in Unix-like operating systems. • It provides and interface between kernel and user space. • It presents information about processes and other system information in a hierarchical file-like structure. • No need for direct access to kernel memory for kernel related information. • It is mapped to a mount point named /proc at boot time. • It can be used to obtain information about the system and to change certain kernel parameters at runtime. 28-02-2018
- 6. Gaurav Mishra <[email protected]> PROCFS files File Description /proc/bus/ Directory of available system bus like input/PCI/USB /proc/cmdline Boot time options passed to kernel /proc/cpuinfo Information about CPU like vendor, speed, etc. /proc/devices List of character and block devices with link in /dev /proc/filesystems List of filesystems supported by kernel at the time of listing /proc/diskstats Information about logical disks installed /proc/meminfo Information about the memory management done by kernel /proc/modules List of loaded kernel modules /proc/net/ Directory containing information about network stack /proc/swaps List of active swap partitions /proc/tty Contains information about current terminals /proc/version Contains kernel version, gcc used to compile kernel, etc. 28-02-2018
- 7. Gaurav Mishra <[email protected]> Process info File Description /proc/PID/cmdline Command used to start the process /proc/PID/cwd Sym link to current working directory of the process /proc/PID/environ Name and values of the process environment /proc/PID/exe Sym link to original executable file (if it exists) /proc/PID/fd/ Directory with sym link for each open file descriptor /proc/PID/fdinfo/ Directory with information about each file descriptor /proc/PID/maps Contains information about mapped files and blocks like heap /proc/PID/root Sym link to root for the current process (generally /) /proc/PID/status Basic information about the process /proc/PID/task Hard link to tasks started by current process Information of each process is stored in /proc/<PID>/ 28-02-2018
- 8. Gaurav Mishra <[email protected]> Sample screenshot 28-02-2018
- 9. Gaurav Mishra <[email protected]> SYSFS • sysfs is a pseudo file system by the Linux kernel which exports information about various kernel subsystems, hardware devices, and associated device drivers from the kernel's device model to user space through virtual files. • These virtual files are also used for their configuring. • sysfs is mounted under the /sys mount point. 28-02-2018
- 10. Gaurav Mishra <[email protected]> SYSFS directories Directory Description /sys/block Contains symbolic links to block devices in /sys/devices /sys/bus List of physical bus available each with their devices and drivers /sys/class List of device classes in kernel and devices as a symbolic link /sys/dev List of devices categorized as block or character /sys/devices Global list of devices discovered by kernel in a hierarchical format /sys/firmware List of firmware objects interfaces /sys/fs List of filesystems supported and their respective attributes /sys/kernel Every kernel related parameters in hierarchical format /sys/module Contains subdirectory of each loaded kernel module /sys/power Files related to power subsystem 28-02-2018