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Interface to file system quotas on UNIX platforms

Project description

The Python file-system quota module allows accessing file system quotas on UNIX platforms from Python scripts. The module is intended mainly for system administrators who have to manage quotas for all the users on their system.

The following operating systems and file systems are supported transparently through a common API.

Supported operating systems:

  • Linux - kernel 2.0.30 - 4.15
  • FreeBSD 3 - 12.1, OpenBSD 2.2 - 6.6 & NetBSD 5 - 9
  • SunOS 4.1.3 (aka Solaris 1)
  • Solaris 2.4 - 2.10
  • HP-UX 9.0x & 10.10 & 10.20 & 11.00
  • IRIX 5.2 & 5.3 & 6.2 - 6.5
  • OSF/1 & Digital Unix 4
  • AIX 4.1, 4.2 and 5.3

Supported file systems:

  • Standard file systems of the platforms listed above
  • NFS (Network file system) on all of the above (i.e. using an integrated RPC client)
  • XFS on Linux and IRIX 6
  • AFS (Andrew File System) on many of the above (see INSTALL)
  • VxFS (Veritas File System) on Solaris 2

Historical note: The C implementation of this module is derived from the Quota module for Perl (also at CPAN). Since its beginnings in 1995, the module was continuously extended by porting to more UNIX platforms and file-systems. Numerous people have contributed to this process; for a complete list of names please see the CHANGES document in the package. In case of build issues, please refer to the INSTALL document within the package.

The following is a copy of the API documentation in file doc/FsQuota.rst

SYNOPSIS

import FsQuota

qObj = FsQuota.Quota(path [,rpc_host=hostname])

(bcount, bsoft, bhard, btime,
 icount, isoft, ihard, itime) =
    qObj.query(uid [,grpquota=1] [,prjquota=1])

qObj.setqlim(uid, bsoft, bhard, isoft, ihard
             [,timereset=1]
             [,grpquota=1] [,prjquota=1])

qObj.sync()

qObj.rpc_opt([option keywords])

for dev, path, type, opts in FsQuota.MntTab(): ...

FsQuota Module

The FsQuota module provides two classes that allow accessing file system quotas from Python scripts:

Instances of the Quota class take as main init parameter a path of a mount point (or any path below the mount point). The instance can then be used to query or modify quota of users or groups within that file system. The class is designed portably, so that the same interfaces work across all file system types and UNIX platforms. (Although there are some extra options during initialization for certain file systems.)

Instances of the MntTab class allow iterating across the mount table. For each entry in the table, it provides the file system type, mount point and options. (Note this class is usually not required to work with the Quota class. It is provided here just for convenience, as the functionality is actually used internally by the Quota class.)

Class FsQuota.Quota

qObj = FsQuota.Quota(path)
qObj = FsQuota.Quota(remote_path, rpc_host=remote_host)

Creates a Quota object that then is used for querying or modifying quotas. In case of special file systems which are known not to suport quota, the creation may raise exception FsQuota.error. However note the absence of an exception is not a guarantee that the file system actually supports quota limits.

Internal behavior: Most importantly, the initialization determines the file system type and thus the access method to be used in following quota operations. Many platforms use the quotactl syscall, but even then the type of device parameter to be passed varies from system to system. It may be the path of a device file (e.g. /dev/sda1) or the path of the mount point or the quotas file at the top of the file system (e.g. /home/quotas). For the rare cases you need this information, it can be queried via the Quota.dev attribute.

The given mount point may also be on a remote file system (e.g. mounted via Network File System, NFS), which has the class transparently query the given host via a remote procedure call (RPC). Note: RPC queries require rquotad(1m) to be running on the target system. If the daemon or host are down, the operations time out after a configurable delay.

When parameter rpc_host is specified, the automatic detection of file system type is omitted. In this case the following operations will address the file system containing the given path on the given remote host using RPC. This mode should normally not be needed, but could for example be used for accessing file systems that are not mounted locally. See also the rpc_opt() method for additional RPC configuration options.

Quota.query()

(bcount,bsoft,bhard,btime, icount,isoft,ihard,itime)
    = qObj.query(uid, [keyword_options...])

Get current usage and quota limits for blocks and files respectively, owned by the given user. The user is specified by a numeric UID. The result is a named tuple of type FsQuota.QueryResult, so that members can be accessed via name as well as via indices:

  1. bcount: Number of 1 kB blocks currently used by inodes owned by the user.
  2. bsoft: Soft limit for block count (or 0 if none)
  3. bhard: Hard limit for block count (or 0 if none)
  4. btime: Time when an exceeded soft block limit turns into a hard limit. This value is meaningless when the soft limit is not exceeded.
  5. icount: Number of inodes (i.e. files) currently owned by the user.
  6. isoft: Soft limit for inode count (or 0 if none)
  7. ihard: Hard limit for inode count (or 0 if none)
  8. itime: Time when an exceeded soft inode limit turns into a hard limit. This value is meaningless when the soft limit is not exceeded.

When a hard limit is reached, the OS will reject any further write with errno EDQUOT (or ENOSPC on older systems). If the soft limit is exceeded, but hard limit not exceeded, writes by this user will fail only after the time indicated by btime or itime respectively is reached. The time is usually set to 7 days after exceeding the soft limit for the first time. These times are expressed as elapsed seconds since 00:00 1/Jan/1970 GMT.

Note when hard and soft limits are both zero, this means there is no limit for that user. (On some platforms the query may fail with error code ESRCH in that case; most however still report valid usage values.)

Optional keyword-only parameters:

grpquota:When parameter grpquota is present and set to a value that evaluates to True, the value in uid is taken as GID and group quotas are queried. Group quotas may not be supported across all platforms (e.g. Linux and other BSD based Unix variants, OSF/1 and AIX - check the quotactl(2) man page on your systems).
prjquota:When parameter prjquota is present and set to a value that evaluates to True, project quotas are queried; this is currently only supported for XFS. Exception FsQuota.error(ENOTSUP) is raised for unsupported file-systems.

It is an error to select both group and project quota in the same query.

Method Quota.setqlim()

qObj.setqlim(uid, bsoft, bhard, isoft, ihard [,keyword options...])

Sets quota limits for the given user. Meanings of parameters uid, bsoft, bhard, isoft and ihard are the same as for the query() method.

Note all the limit values are optional and default to zero. The parameters can also be passed in form of keyword parameters. For example qObj.setqlim(uid, isoft=10,ihard=20) would limit inode counts to 10 soft, 20 hard, but remove limits for block count. (Note it’s not possible to set only block or inode limits repsectively; to do so query current limits first and then pass those values to setqlim if you want to keep them unchanged.)

Note: if you want to set the quota of a particular user to zero, i.e. no write permission, you must not set all limits to zero, since that is equivalent to unlimited access. Instead set only the hard limit to 0 and the soft limit to a non-zero value.

Optional keyword-only parameters:

timereset:Optional parameter timereset defines how time limits are initialized: When the assigned value is False, time limits are set to NOT STARTED (i.e. the time limits are not initialized until the first write attempt by this user). This is the default when the parameter is omitted. When assigned True, the time limits are set to 7.0 days. More alternatives (i.e. setting a specific time) aren’t available in most implementations.
grpquota:When parameter grpquota is present and set to True, parameter uid is interpreted as GID and the the limit of the corresponding group is modified. This is not supported on all platforms.
prjquota:When parameter prjquota is present and set to True, project quotas are modified; this is currently only supported for XFS. Exception FsQuota.error(ENOTSUP) is raised for unsupported file-systems.

It is an error to select both group and project quota in the same query.

Note that the class does not support setting quotas via RPC (even though some implementations of rpc.rquotad(8) allow optionally enabling this, but it seems a bad idea for security.)

Method Quota.sync()

qObj.sync()

Have the kernel update the quota file on disk, in particular after modifying quota limits.

A secondary purpose of this method is checking if quota support is enabled in the kernel (and on some platforms, for a particular file system; on others however the call succeeds even if quota is not enabled in the given file system.) Read the quotaon(1m) man page on how to enable quotas on a file system.

Method Quota.rpc_opt()

qObj.rpc_opt([keyword options...])

This method allows configuring networking and authentication parameters for queries of network file system quotas via RPC. The options have no effect when targeting other file system types. The following keyword-only parameters are available:

rpc_port:Sets the port used by rpc.rquotad(8); default value is zero, which which means the remote host’s portmapper (aka rpcbind) is used. (Note in case of the latter you can find out the port using rpcinfo -p host)
rpc_use_tcp:If True, use TCP; if False use UDP (default).
rpc_timeout:Timeout value in milliseconds in case the remote host does not respond.
auth_uid:UID value (i.e. user identifier) to provide for authentication. If not specified, this defaults to the UID of the current process. For example, you could set the UID here that you later want to query, for circumventing a permission error.
auth_gid:GID value (i.e. group identifier) to provide for authentication. If not specified, this defaults to the GID of the current process.
auth_hostname:Hostname to provide for authentication. If not specified or empty, this defaults to the name of the local machine.

Note for resetting to default authentication, set both auth_uid and auth_gid to value -1 (even if you previously changed only one, as the opposite is filled in automatically if missing).

Attribute Quota.dev

This attribute provides the device argument used internally by query() and setqlim() methods for the selected file system.

Attribute Quota.is_nfs

This attribute indicates 1 is the file system is NFS, else 0.

Class FsQuota.MntTab()

This class defines objects that can be used as an iterator which lists all entries in the mount table. Each object returned by iteration is a named tuple of type FsQuota.MntEnt with the following entries of type string:

  1. mnt_fsname: Name of the filesystem (e.g. device name)
  2. mnt_dir: Filesystem path prefix (aka mount point)
  3. mnt_type: Mount type (aka file system type)
  4. mnt_opts: Mount options, separated by colon.

Note the mount table contains information about all currently mounted (local or remote) file systems. The format and location of this table varies from system to system (e.g. it may be in file /etc/mtab). This iterator provides a portable way to read it. (On some systems, like OSF/1, this table isn’t accessible as a file at all, i.e. only via C library interfaces). Internally, the iterator will call setmntent(3) or the equivalent of your platform upon initialization, call getmntent(3) during iteration, and call endmntent(3) upon deallocation.

Hint: For finding the mount table entry corresponding to a given path (e.g. to determine the file system type), you can compare the device ID indicated by os.stat(path).st_dev of the mount points returned from iteration with that of the path in question.

ERROR HANDLING

All methods raise exception FsQuota.error upon errors. The exception class is derived from exception OSError and thus contains firstly a numerical error code in attribute errno (copied from errno in most cases), secondly a derived error message in attribute strerror, and when applicable, thirdly a file name in attribute filename.

Note the error string is adapted to the context of quota operations and therefore not always identical to the text returned by strerror(ex.errno). This is necessary as normal error descriptions don’t always make sense for quota errors (e.g. ESRCH: No such process, here: No quota for this user)

AUTHORS

This module is derived from an equivalent extension module for Perl, created 1995 by T. Zoerner (email: tomzo AT users.sourceforge.net) and since then continuously improved and ported to many more operating systems and file systems - and now ported to Python. Numerous people have contributed to this process in the past; for a complete list of names please see the CHANGES document.

LICENSE

Copyright (C) 1995-2020 T. Zoerner

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation. (Either version 2 of the GPL, or any later version, see http://www.opensource.org/licenses/).

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

SEE ALSO

python3(1), edquota(8), quotactl(2) or quotactl(7I), mount(8), mtab(4) or mnttab(4), quotaon(8), setmntent(3), getmntent(3) or getmntinfo(3), endmntent(3), rpc(3), rquotad(8) or rpc.rquotad(8), rpcinfo(7).

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