| Sun StorageTek QFS File System Configuration and Administration Guide |    
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| Sun StorageTek QFS File System Configuration and Administration Guide |
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| C H A P T E R 5 |
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Administering File System Quotas |
This chapter describes how to enable and administer file system quotas. This chapter contains the following sections:
File system quotas control the amounts of online and total disk space that can be consumed by a specific user, by a group of users, or by a site-determined group of users called an admin set.
Quotas help control the size of a file system by limiting the amount of space and the number of inodes that each user can consume. Quotas can be especially useful on file systems that contain user home directories. After quotas are enabled, you can monitor usage and adjust the quotas as needs change.
A file system provides a user with blocks for data and inodes for files. Each file uses one inode, and file data is stored in a disk allocation unit (DAU). DAU sizes are determined at the time the file system is created. Quotas account for disk usage in multiples of 512 bytes.
The following subsections provide background information about using quotas:
You can set quotas according to user ID, group ID, or an administrator's site-specific grouping. This site-specific grouping is called an admin set ID. You can use an admin set ID, for example, to identify a collection of users working on a project for which file system quotas are imposed.
Quotas are enabled when the quota mount option is in effect and the system detects the presence of one or more quota files in the file system's root directory. The quota mount option is enabled by default. If you mount the file system with noquota in effect, quotas are disabled. For more information about mount options, see the mount_samfs(1M) man page.
Each quota file contains a sequence of records. Record zero is the record for the system administrator's quotas and resource usage. System administrator quotas are never enforced, but you can use any record, including the system administrator's record, as a template for subsequent records in the quota file. For more information about this practice, see To Enable or Change Limits for Users, Groups, or Admin Sets Using an Existing Quota File.
Record one is the record in the quota file for user one, group one, or admin set ID one, depending on the type of quota file. You can edit record one and all subsequent records in order to set different quotas for different users. TABLE 5-1 shows the quota file names and the quotas they enable in /root.
You can set default quota limits for users by editing record zero in the quota file and allowing the values in record zero to be used as the initial quota settings for all other users. By default, if user quota limits have not been set specifically, the system uses the values in record zero.
Each quota file requires 128 bytes of space. To calculate the necessary size for the initial zero quota file, use the following formula:
(highest-ID + 1) x 128 = x
x / 4096 = zero quota file size
You can set both soft and hard limits. A hard limit specifies a fixed amount of system resources available for use, which the system never allows a user to exceed. A soft limit specifies a level of system resource use that can be exceeded temporarily, up to the hard limit. The soft limit is never larger than the hard limit.
If a user attempts to allocate resources beyond the hard limit, the operation is aborted. In this case, the operation fails and generates an EDQUOT error.
After a user exceeds a soft limit, a timer starts, and the user enters a grace period. While the timer is ticking, the user is allowed to operate above the soft limit. After the user goes below the soft limit, the timer is reset. If the grace period ends and the timer stops without the user's having gone below the soft limit, the soft limit is then enforced as a hard limit.
For example, assume that a user has a soft limit of 10,000 blocks and a hard limit of 12,000 blocks. If the user's block usage exceeds 10,000 blocks and the timer exceeds the grace period, this user is no longer able to allocate more disk blocks on that file system until usage drops below the 10,000-block soft limit.
You, the administrator, can use the samquota(1M) command to see the timer value. The squota(1) command is a user version of the samquota(1M) command. The squota(1) user command contains options that users can specify to obtain information about quotas that pertain to them.
It is possible for a user to exceed an inode quota, without using any blocks, by creating all empty files. It is also possible for a user to use only one inode and still exceed the block quota by creating a file that is large enough to consume all data blocks in the user's quota.
File system quotas are expressed in terms of the number of 512-byte blocks that a user can allocate. However, disk space is allocated to user files in terms of DAUs. The DAU setting is specified by the -a allocation-unit option to the sammkfs(1M) command. It is preferable to set a block quota to a multiple of the file system DAU. If this is not done, users can allocate only up to the block count, rounded down to the nearest DAU. See Enabling Default Quota Values for instructions on setting block quotas.
You can enable quotas through a process that includes editing system files, creating quota files, and entering various quota commands.
The following subsections provide more details on how to configure a file system to use quotas and how to enable quotas.
Before you enable quotas, you should determine how much disk space and how many inodes to allocate to each user. If you want to be sure that the total file system space is never exceeded, you can divide the total size of the file system by the number of users. For example, if three users share a 100-megabyte slice and have equal disk space needs, you could allocate 33 megabytes to each. In environments in which not all users are likely to reach their limits, you might want to set individual quotas so that they add up to more than the total size of the file system. For example, if three users shared a 100-megabyte slice, you could allocate 40 megabytes to each.
You can use the following quota commands, in the formats shown, for displaying quota information:
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Use this procedure if you are creating a new file system and no files currently reside in the file system. To configure an existing file system to use quotas, see To Configure an Existing File System to Use Quotas.
Before you start this procedure, make sure that you do not have the noquota mount option specified in your samfs.cmd or /etc/vfstab files.
Either follow the steps outlined in the Sun StorageTek QFS Installation and Upgrade Guide, or use the examples in Configuration Examples to create the mcf file, create the mount point, initialize the file system, and so on.
3. Use the mount(1M) command to mount the file system.
4. Use the dd(1M) command to create the quota files.
The arguments to this command depend on the type of quota you are creating, as follows:
For more information about the dd(1M) command, see the dd(1M) man page.
5. Use the umount(1M) command to unmount the file system in which the quota files have been created.
The file system must be unmounted so it can be remounted and have its quota files read at mount time. For more information about the umount(1M) command, see the umount(1M) man page.
6. Use the samfsck(1M) command to perform a file system check.
In the following example, the -F option resets the in-use values in the quota files:
7. Use the mount(1M) command to remount the file system.
The system enables quotas when it detects the presence of one or more quota files in the root directory.
For more information about the mount(1M) command, see the mount_samfs(1M) man page.
8. Use the samquota(1M) command to set quotas for users, groups, or admin sets.
Subsequent sections in this chapter provide procedures and show examples of this process. For more information about the samquota(1M) command, see the samquota(1M) man page.
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Use this procedure if you are creating quotas for a file system that is already populated with files. If you are configuring a new file system to use quotas, see To Configure a New File System to Use Quotas.
Before you start this procedure, make sure that you do not have the noquota mount option specified in your samfs.cmd or /etc/vfstab files.
1. Use the su(1) command to become superuser.
2. Use the mount(1M) command to examine the /etc/mnttab file and ensure that the file system is mounted:
Make sure that the file system is listed in the mount list that is displayed.
3. Use the cd(1) command to change to the root directory of the file system for which quotas are to be enabled.
4. Use the ls(1) -a command to retrieve the list of files in this directory and verify that quotas do not already exist on the file system.
If any of the following files are present, quotas have been enabled for this file system: .quota_u, .quota_g, .quota_a.
If any quota type is established for a file system, you can establish any other quota type later. Be careful not to modify existing quota files when adding new ones.
5. If the quota files do not exist for the types of quotas you wish to enforce, use the dd(1M) command to create the quota files.
Determine the highest existing ID numbers of the types of quotas you wish to enforce. Make the initial, zero, quota files large enough to hold the records for those IDs; each quota file record requires 128 bytes.
For example, if you want to enable admin set quotas, and the highest admin set ID in use on the file system is 1024, the calculation is as follows:
For more information about the dd(1M) command, see the dd(1M) man page.
6. Use the umount(1M) command to unmount the file system in which the quota files have been created.
The file system must be unmounted so it can be remounted and have its quota files read at mount time. For more information about unmounting a file system, see Unmounting a File System.
7. Use the samfsck(1M) -F command to perform a file system check.
This command updates records allocated in the quota files with correct, current usage information.
8. Use the mount(1M) command to remount the file system in which the quota files have been created.
The system enables quotas when it detects the presence of one or more quota files in the /root directory.
You do not need to include the quota mount option in the /etc/vfstab or samfs.cmd file. The quota mount option is enabled by default with the mount(1M) command, and quotas are enabled automatically when the system detects the presence of quota files.
For more information about the mount(1M) command, see the mount_samfs(1M) man page.
9. Use the samquota(1M) command to set quotas for users, groups, or admin sets.
Subsequent sections in this chapter provide procedures and show examples of this process. For more information about the samquota(1M) command, see the samquota(1M) man page.
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1. Use the su(1) command to become superuser.
Use the samchaid(1M) command to change the admin set IDs for the directory or file, as follows:
For more information about the samchaid(1M) command, see the samchaid(1M) man page.
An infinite quota is a kind of special quota. Users with infinite quotas are never denied access to any available file system resource. You can set infinite quota values into record zero of the user, group, or admin set ID quota files and then use this record as the default value for a new user, group, or admin set ID.
Use the samquota(1M) command to set the quota limit to zero.
You can use the samquota(1M) command to set infinite quotas for particular users, groups, or admin set IDs by setting zero values for all hard and soft limits. CODE EXAMPLE 5-2 shows how to set infinite quotas.
You can use the samquota(1M) command to enable a default quota for a user, group, or admin set. This is accomplished through default limits in user, group, or admin set zero.
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For example, the following samquota(1M) command sets default quotas for all admin set IDs:
The preceding command sets any user's uninitialized admin set quota limits as follows:
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Note - If a quota record already exists, the existing values remain in effect. This occurs, for example, if the admin group already has blocks assigned to it. |
You can set similar default quotas for users or groups by specifying -U 0 or -G 0, respectively, in place of -A 0.
For more information about the
You can use the samquota(1M) command to enable a set of limits for a particular user, group, or admin set.
CODE EXAMPLE 5-3 shows commands that enable limits for users, groups, and admin sets, respectively.
For more information about the samquota(1M) command, see the samquota(1M) man page.
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After quotas are established, you can use an existing quota file as a template when creating limits for another user, group, or admin set. The following procedure shows this. You can also use this procedure to change any of the quota settings.
1. Use the samquota(1M) command to retrieve a quota file, and direct the output to a temporary file.
Use the -e option with one or more of the following additional options: -U userID,
-G groupID, or -A adminsetID.
CODE EXAMPLE 5-4 shows how to create and retrieve file quota.group to use as a template.
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Note - You can use a group quota entry as a template to create a user quota entry. |
2. Use an editor to edit the temporary file you just created.
CODE EXAMPLE 5-5 shows the file that was generated in Step 1 opened in the vi(1) editor. Group ID 101 has been changed to 102. This has the effect of generating a command to copy the quotas set for group 101 to group 102.
3. Save the file and exit the editor.
4. To apply the changes made in the editor, execute the file using the shell.
In this example, the -x option directs the shell to echo the commands it executes. You can omit the -x option if desired.
After you have enabled disk and inode quotas, you can check these quotas. The samquota(1M) command is an administrator command that generates a quota report on an individual user, group, or admin set. The squota(1) command is a user command that enables users to check their own individual quotas.
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2. Use the samquota(1M) command to display the quotas in effect for mounted file systems.
For userID, specify the numeric user ID or user name of the user whose quotas are being examined.
For file, specify a specific file system for the selected user, group, or admin set. The file argument can also be the name of any file in the file system. Typically, file is the name of the root directory of the file system.
Example 1. CODE EXAMPLE 5-6 retrieves user hm1259's quota statistics in the sam6 file system on the server and displays output indicating that this user is not exceeding the quota.
Example 2. CODE EXAMPLE 5-7 retrieves user memil's quota statistics in all mounted Sun StorageTek QFS file systems and displays output indicating that this user is exceeding the quota. Note the plus sign (+) in the Blocks row of the output. The plus sign would appear in the Files row, too, if the soft quota limit were being exceeded for files.
If a hard limit has been exceeded, or if the soft limit has been exceeded and the grace period has expired, the offending In Use field is marked with an asterisk character (*). If a quota record's limits are determined to be inconsistent (for example, if a soft limit is larger than a hard limit), an exclamation point is used to mark the field, and all allocation operations are prevented.
For groupID, specify the numeric group ID or the group name for the group of users whose quotas are being examined. For file, specify a specific file system for the selected group. The file argument can also be the name of any file in the file system. Typically, file is the name of the root directory of the file system.
For example, the following command retrieves user quota statistics for the group turtles in the qfs3 file system:
For adminsetID, specify the numeric admin set ID of the site-specific administrator set whose quotas are being examined. For file, specify a specific file system for the selected admin set. The file argument can also be the name of any file in the file system. Typically, file is the name of the root directory of the file system.
For example, the following command retrieves user quota statistics for the admin set 457 in all mounted Sun StorageTek QFS file systems:
You can change quotas to adjust the amount of disk space or number of inodes allocated to users. You can also remove quotas from users or from an entire file system. The following subsections describe how to change and remove quotas:
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You can use the samquota(1M) command to change the soft time limit grace period.
1. Use the samquota(1M) command to retrieve quota statistics for a user, group, or admin set.
See To Check for Exceeded Quotas for instructions.
Example. CODE EXAMPLE 5-8 retrieves information about group sam and shows that this group is over its soft limit.
2. Examine the output from the samquota(1M) command and determine what the new limits should be.
3. Use the samquota(1M) command to change the soft time limit grace period.
CODE EXAMPLE 5-9 shows using the samquota(1M) command options to use.
# samquota -U userID -t interval file # samquota -G groupID -t interval file # samquota -A adminID -t interval file |
The arguments for these commands are as follows:
For example, suppose that you wanted to change the grace period for user memil. CODE EXAMPLE 5-10 shows the samquota(1M) command that you would use to verify the quotas and its output.
You would enter the following command to shorten the grace period.
CODE EXAMPLE 5-11 shows the samquota(1M) command that you would then use to verify the new quotas.
If a user has exceeded the soft quota limit, changing the grace period itself does not modify the expiration timer of any grace periods that have already started. If the grace period is already in effect, you can use the samquota(1M) command to modify the grace period in one of the following ways:
CODE EXAMPLE 5-12 shows the command used to clear the timer so it starts counting the next time a user in group sam attempts to allocate a block or file in /sam6.
CODE EXAMPLE 5-13 resets the grace period.
CODE EXAMPLE 5-14 sets a very long expiration period.
CODE EXAMPLE 5-15 expires the grace period.
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When the file system detects that quota values are not consistent for a user, group, or admin set, it prevents that user, group, or admin set from using any more system resources. You can inhibit file system resource allocations by creating inconsistent quota values. For example, you can inhibit further allocation if the hard block or file limits are lower than the soft block or file limits, or if a user's soft limit is larger than the user's hard limit.
The file system treats an inconsistent quota setting as a special quota. You can set inconsistent quota values into record zero of the user, group, or admin set ID quota files, and from there they can become the default values for new users, groups, or admin set IDs.
The following procedure shows how to inhibit further system resource allocations for a user, group, or admin set.
2. Obtain, save, and examine current quota information.
CODE EXAMPLE 5-16 shows how to use the samquota(1M) command to retrieve current group quota information for group sam and write it to a backup file.
To obtain quota information about a user quota, specify the -U userID option in place of the -G option. To obtain quota information about an admin set quota, specify the -A adminID option in place of the -G option.
3. Use the samquota(1M) command to set soft quotas to nonzero quotas and hard quotas to zero quotas.
The following command sets the quotas for group sam to be inconsistent:
To make the quotas for users or admin sets inconsistent, specify the -U userID or
-A adminID option in place of the -G option.
4. Use the samquota(1M) command to verify your changes.
CODE EXAMPLE 5-17 shows this.
In the preceding output, a zero quota is in effect. Note the exclamation point characters (!), which indicate the over-quota condition in the output.
5. Use the sh(1) and samquota(1M) commands to restore the group's quota to what it was before the file/block allocation was inhibited and then to verify the changed quotas.
CODE EXAMPLE 5-18 shows these commands.
To perform this operation on a user quota, specify the -U userID option in place of the -G option. To perform this operation on an admin set quota, specify the
-A adminID option in place of the -G option.
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To remove or disable quotas for a file system, you need to disable quotas in the mount process.
1. Use the su(1) command to become superuser.
2. (Optional) Use a text editor to add the noquota mount option to the /etc/vfstab or samfs.cmd file.
Alternatively, you can specify noquota as an option later, when you issue the mount command. See Step 4.
3. If the file system is mounted, use the umount(1M) command to unmount the file system.
If you have difficulty unmounting the file system, see Unmounting a File System.
4. Remount the file system using the mount(1M) command.
If you did not perform Step 2, include the noquota option with the mount(1M) command.
5. Dispense with the quota files by doing one of the following:
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2. If the file system is mounted, use the umount(1M) command to unmount the file system.
If you have difficulty unmounting the file system, see Unmounting a File System.
3. Use the samfsck(1M) -F command to perform a file system check.
The samfsck(1M) command updates records allocated in the quota files with correct, current usage information.
4. Use the mount(1M) command to remount the file system.
| Sun StorageTek QFS File System Configuration and Administration Guide | 819-7935-10 |
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Copyright © 2007, Sun Microsystems, Inc. All Rights Reserved.
To Configure a New File System to Use Quotas