{ "content": [ { "type": "text", "text": "# BTRFS-QGROUP (man)\n\n## NAME\n\nbtrfs-qgroup - control the quota group of a btrfs filesystem\n\n## SYNOPSIS\n\nbtrfs qgroup \n\n## DESCRIPTION\n\nbtrfs qgroup is used to control quota group (qgroup) of a btrfs filesystem.\n\n## Sections\n\n- **NAME**\n- **SYNOPSIS**\n- **DESCRIPTION**\n- **QGROUP**\n- **SUBCOMMAND**\n- **QUOTA RESCAN**\n- **EXAMPLES** (1 subsections)\n- **EXIT STATUS**\n- **AVAILABILITY**\n- **SEE ALSO**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n" } ], "structuredContent": { "command": "BTRFS-QGROUP", "section": "", "mode": "man", "summary": "btrfs-qgroup - control the quota group of a btrfs filesystem", "synopsis": "btrfs qgroup ", "tldr_summary": null, "tldr_examples": [], "tldr_source": null, "flags": [], "examples": [ "Given the following filesystem mounted at /mnt/my-vault", "Label: none uuid: 60d2ab3b-941a-4f22-8d1a-315f329797b2", "Total devices 1 FS bytes used 128.00KiB", "devid 1 size 5.00GiB used 536.00MiB path /dev/vdb", "Enable quota and create subvolumes. Check subvolume ids.", "$ cd /mnt/my-vault", "$ btrfs quota enable .", "$ btrfs subvolume create a", "$ btrfs subvolume create b", "$ btrfs subvolume list .", "ID 261 gen 61 top level 5 path a", "ID 262 gen 62 top level 5 path b", "Create qgroup and set limit to 10MiB.", "$ btrfs qgroup create 1/100 .", "$ btrfs qgroup limit 10M 1/100 .", "$ btrfs qgroup assign 0/261 1/100 .", "$ btrfs qgroup assign 0/262 1/100 .", "And check qgroups.", "$ btrfs qgroup show .", "qgroupid rfer excl", "-------- ---- ----", "0/5 16.00KiB 16.00KiB", "0/261 16.00KiB 16.00KiB", "0/262 16.00KiB 16.00KiB", "1/100 32.00KiB 32.00KiB" ], "see_also": [ { "name": "mkfs.btrfs", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/mkfs.btrfs/8/json" }, { "name": "btrfs-subvolume", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/btrfs-subvolume/8/json" }, { "name": "btrfs-quota", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/btrfs-quota/8/json" } ], "section_outline": [ { "name": "NAME", "lines": 2, "subsections": [] }, { "name": "SYNOPSIS", "lines": 2, "subsections": [] }, { "name": "DESCRIPTION", "lines": 8, "subsections": [] }, { "name": "QGROUP", "lines": 17, "subsections": [] }, { "name": "SUBCOMMAND", "lines": 119, "subsections": [] }, { "name": "QUOTA RESCAN", "lines": 12, "subsections": [] }, { "name": "EXAMPLES", "lines": 1, "subsections": [ { "name": "Example 1. Make a parent group that has two quota group children", "lines": 35 } ] }, { "name": "EXIT STATUS", "lines": 3, "subsections": [] }, { "name": "AVAILABILITY", "lines": 3, "subsections": [] }, { "name": "SEE ALSO", "lines": 5, "subsections": [] } ], "sections": { "NAME": { "content": "btrfs-qgroup - control the quota group of a btrfs filesystem\n", "subsections": [] }, "SYNOPSIS": { "content": "btrfs qgroup \n", "subsections": [] }, "DESCRIPTION": { "content": "btrfs qgroup is used to control quota group (qgroup) of a btrfs filesystem.\n\nNote\nTo use qgroup you need to enable quota first using btrfs quota enable command.\n\nWarning\nQgroup is not stable yet and will impact performance in current mainline kernel (v4.14).\n", "subsections": [] }, "QGROUP": { "content": "Quota groups or qgroup in btrfs make a tree hierarchy, the leaf qgroups are attached to\nsubvolumes. The size limits are set per qgroup and apply when any limit is reached in tree\nthat contains a given subvolume.\n\nThe limits are separated between shared and exclusive and reflect the extent ownership. For\nexample a fresh snapshot shares almost all the blocks with the original subvolume, new writes\nto either subvolume will raise towards the exclusive limit.\n\nThe qgroup identifiers conform to level/id where level 0 is reserved to the qgroups\nassociated with subvolumes. Such qgroups are created automatically.\n\nThe qgroup hierarchy is built by commands create and assign.\n\nNote\nIf the qgroup of a subvolume is destroyed, quota about the subvolume will not be\nfunctional until qgroup 0/ is created again.\n", "subsections": [] }, "SUBCOMMAND": { "content": "assign [options] \nAssign qgroup as the child qgroup of in the btrfs filesystem identified by\n.\n\nOptions\n\n--rescan\n(default since: 4.19) Automatically schedule quota rescan if the new qgroup\nassignment would lead to quota inconsistency. See QUOTA RESCAN for more information.\n\n--no-rescan\nExplicitly ask not to do a rescan, even if the assignment will make the quotas\ninconsistent. This may be useful for repeated calls where the rescan would add\nunnecessary overhead.\n\ncreate \nCreate a subvolume quota group.\n\nFor the 0/ qgroup, a qgroup can be created even before the subvolume is\ncreated.\n\ndestroy \nDestroy a qgroup.\n\nIf a qgroup is not isolated, meaning it is a parent or child qgroup, then it can only be\ndestroyed after the relationship is removed.\n\nlimit [options] |none [] \nLimit the size of a qgroup to or no limit in the btrfs filesystem identified by\n.\n\nIf is not given, qgroup of the subvolume identified by is used if\npossible.\n\nOptions\n\n-c\nlimit amount of data after compression. This is the default, it is currently not\npossible to turn off this option.\n\n-e\nlimit space exclusively assigned to this qgroup.\n\nremove \nRemove the relationship between child qgroup and parent qgroup in the btrfs\nfilesystem identified by .\n\nOptions\n\n--rescan\n(default since: 4.19) Automatically schedule quota rescan if the removed qgroup\nrelation would lead to quota inconsistency. See QUOTA RESCAN for more information.\n\n--no-rescan\nExplicitly ask not to do a rescan, even if the removal will make the quotas\ninconsistent. This may be useful for repeated calls where the rescan would add\nunnecessary overhead.\n\nshow [options] \nShow all qgroups in the btrfs filesystem identified by .\n\nOptions\n\n-p\nprint parent qgroup id.\n\n-c\nprint child qgroup id.\n\n-r\nprint limit of referenced size of qgroup.\n\n-e\nprint limit of exclusive size of qgroup.\n\n-F\nlist all qgroups which impact the given path(include ancestral qgroups)\n\n-f\nlist all qgroups which impact the given path(exclude ancestral qgroups)\n\n--raw\nraw numbers in bytes, without the B suffix.\n\n--human-readable\nprint human friendly numbers, base 1024, this is the default\n\n--iec\nselect the 1024 base for the following options, according to the IEC standard.\n\n--si\nselect the 1000 base for the following options, according to the SI standard.\n\n--kbytes\nshow sizes in KiB, or kB with --si.\n\n--mbytes\nshow sizes in MiB, or MB with --si.\n\n--gbytes\nshow sizes in GiB, or GB with --si.\n\n--tbytes\nshow sizes in TiB, or TB with --si.\n\n--sort=[+/-][,[+/-]]...\nlist qgroups in order of .\n\n can be one or more of qgroupid,rfer,excl,maxrfer,maxexcl.\n\nPrefix '+' means ascending order and '-' means descending order of . If no\nprefix is given, use ascending order by default.\n\nIf multiple s is given, use comma to separate.\n\n--sync\nTo retrieve information after updating the state of qgroups, force sync of the\nfilesystem identified by before getting information.\n", "subsections": [] }, "QUOTA RESCAN": { "content": "The rescan reads all extent sharing metadata and updates the respective qgoups accordingly.\n\nThe information consists of bytes owned exclusively (excl) or shared/referred to (rfer).\nThere’s no explicit information about which extents are shared or owned exclusively. This\nmeans when qgroup relationship changes, extent owners change and qgroup numbers are no longer\nconsistent unless we do a full rescan.\n\nHowever there are cases where we can avoid a full rescan, if a subvolume whose rfer number\nequals its excl number, which means all bytes are exclusively owned, then assigning/removing\nthis subvolume only needs to add/subtract rfer number from its parent qgroup. This can speed\nup the rescan.\n", "subsections": [] }, "EXAMPLES": { "content": "", "subsections": [ { "name": "Example 1. Make a parent group that has two quota group children", "content": "Given the following filesystem mounted at /mnt/my-vault\n\nLabel: none uuid: 60d2ab3b-941a-4f22-8d1a-315f329797b2\nTotal devices 1 FS bytes used 128.00KiB\ndevid 1 size 5.00GiB used 536.00MiB path /dev/vdb\n\nEnable quota and create subvolumes. Check subvolume ids.\n\n$ cd /mnt/my-vault\n$ btrfs quota enable .\n$ btrfs subvolume create a\n$ btrfs subvolume create b\n$ btrfs subvolume list .\n\nID 261 gen 61 top level 5 path a\nID 262 gen 62 top level 5 path b\n\nCreate qgroup and set limit to 10MiB.\n\n$ btrfs qgroup create 1/100 .\n$ btrfs qgroup limit 10M 1/100 .\n$ btrfs qgroup assign 0/261 1/100 .\n$ btrfs qgroup assign 0/262 1/100 .\n\nAnd check qgroups.\n\n$ btrfs qgroup show .\n\nqgroupid rfer excl\n-------- ---- ----\n0/5 16.00KiB 16.00KiB\n0/261 16.00KiB 16.00KiB\n0/262 16.00KiB 16.00KiB\n1/100 32.00KiB 32.00KiB\n" } ] }, "EXIT STATUS": { "content": "btrfs qgroup returns a zero exit status if it succeeds. Non zero is returned in case of\nfailure.\n", "subsections": [] }, "AVAILABILITY": { "content": "btrfs is part of btrfs-progs. Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for\nfurther details.\n", "subsections": [] }, "SEE ALSO": { "content": "mkfs.btrfs(8), btrfs-subvolume(8), btrfs-quota(8),\n\n\n\nBtrfs v5.16.2 02/16/2022 BTRFS-QGROUP(8)", "subsections": [] } } } }