NAMEtmpfiles.d - Configuration for creation, deletion and cleaning of volatile and temporary files
systemd-tmpfiles uses the configuration files from the above directories to describe the creation, cleaning and removal of volatile and temporary files and directories which usually reside in directories such as /run or /tmp.
Volatile and temporary files and directories are those located in /run (and its alias /var/run), /tmp, /var/tmp, the API file systems such as /sys or /proc, as well as some other directories below /var.
System daemons frequently require private runtime directories below /run to place communication sockets and similar in. For these, consider declaring them in their unit files using RuntimeDirectory= (see systemd.exec(5) for details), if this is feasible.
Each configuration file shall be named in the style of package.conf or package-part.conf. The second variant should be used when it is desirable to make it easy to override just this part of configuration.
Files in /etc/tmpfiles.d override files with the same name in /usr/lib/tmpfiles.d and /run/tmpfiles.d. Files in /run/tmpfiles.d override files with the same name in /usr/lib/tmpfiles.d. Packages should install their configuration files in /usr/lib/tmpfiles.d. Files in /etc/tmpfiles.d are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. All configuration files are sorted by their filename in lexicographic order, regardless of which of the directories they reside in. If multiple files specify the same path, the entry in the file with the lexicographically earliest name will be applied. All other conflicting entries will be logged as errors. When two lines are prefix and suffix of each other, then the prefix is always processed first, the suffix later. Lines that take globs are applied after those accepting no globs. If multiple operations shall be applied on the same file, (such as ACL, xattr, file attribute adjustments), these are always done in the same fixed order. Otherwise, the files/directories are processed in the order they are listed.
If the administrator wants to disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in /etc/tmpfiles.d/ bearing the same filename.
The configuration format is one line per path containing type, path, mode, ownership, age, and argument fields:
#Type Path Mode UID GID Age Argument d /run/user 0755 root root 10d - L /tmp/foobar - - - - /dev/null
Fields may be enclosed within quotes and contain C-style escapes.
The type consists of a single letter and optionally an exclamation mark.
The following line types are understood:
- Create a file if it does not exist yet. If the argument parameter is given, it will be written to the file. Does not follow symlinks.
- Create or truncate a file. If the argument parameter is given, it will be written to the file. Does not follow symlinks.
- Write the argument parameter to a file, if the file exists. Lines of this type accept shell-style globs in place of normal path names. The argument parameter will be written without a trailing newline. C-style backslash escapes are interpreted. Follows symlinks.
- Create a directory. The mode and ownership will be adjusted if specified and the directory already exists. Contents of this directory are subject to time based cleanup if the age argument is specified.
- Similar to d, but in addition the contents of the directory will be removed when --remove is used.
- Similar to d, but the directory will not be created if it does not exist. Lines of this type accept shell-style globs in place of normal path names. For this entry to be useful, at least one of the mode, uid, gid, or age arguments must be specified, since otherwise this entry has no effect. If the age argument is "0", contents of the directory will be unconditionally deleted every time systemd-tmpfiles --clean is run. This can be useful when combined with !, see the examples.
- Create a subvolume if the path does not exist yet, the file system supports subvolumes (btrfs), and the system itself is installed into a subvolume (specifically: the root directory / is itself a subvolume). Otherwise, create a normal directory, in the same way as d. A subvolume created with this line type is not assigned to any higher-level quota group. For that, use q or Q, which allow creating simple quota group hierarchies, see below.
- Similar to v. However, makes sure that the subvolume will be assigned to the same higher-level quota groups as the subvolume it has been created in. This ensures that higher-level limits and accounting applied to the parent subvolume also include the specified subvolume. On non-btrfs file systems, this line type is identical to d. If the subvolume already exists and is already assigned to one or more higher level quota groups, no change to the quota hierarchy is made. Also see Q below. See btrfs-qgroup(8) for details about the btrfs quota group concept.
q. However, instead of copying the higher-level quota group assignments from the parent as-is, the lowest quota group of the parent subvolume is determined that is not the leaf quota group. Then, an "intermediary" quota group is inserted that is one level below this level, and shares the same ID part as the specified subvolume. If no higher-level quota group exists for the parent subvolume, a new quota group at level 255 sharing the same ID as the specified subvolume is inserted instead. This new intermediary quota group is then assigned to the parent subvolume's higher-level quota groups, and the specified subvolume's leaf quota group is assigned to it.
Effectively, this has a similar effect as q, however introduces a new higher-level quota group for the specified subvolume that may be used to enforce limits and accounting to the specified subvolume and children subvolume created within it. Thus, by creating subvolumes only via q and Q, a concept of "subtree quotas" is implemented. Each subvolume for which Q is set will get a "subtree" quota group created, and all child subvolumes created within it will be assigned to it. Each subvolume for which q is set will not get such a "subtree" quota group, but it is ensured that they are added to the same "subtree" quota group as their immediate parents.
It is recommended to use Q for subvolumes that typically contain further subvolumes, and where it is desirable to have accounting and quota limits on all child subvolumes together. Examples for Q are typically /home or /var/lib/machines. In contrast, q should be used for subvolumes that either usually do not include further subvolumes or where no accounting and quota limits are needed that apply to all child subvolumes together. Examples for q are typically /var or /var/tmp. As with Q, q has no effect on the quota group hierarchy if the subvolume exists and already has at least one higher-level quota group assigned.
- Create a named pipe (FIFO) if it does not exist yet. If suffixed with + and a file already exists where the pipe is to be created, it will be removed and be replaced by the pipe.
- Create a symlink if it does not exist yet. If suffixed with + and a file already exists where the symlink is to be created, it will be removed and be replaced by the symlink. If the argument is omitted, symlinks to files with the same name residing in the directory /usr/share/factory/ are created. Note that permissions and ownership on symlinks are ignored.
- Create a character device node if it does not exist yet. If suffixed with + and a file already exists where the device node is to be created, it will be removed and be replaced by the device node. It is recommended to suffix this entry with an exclamation mark to only create static device nodes at boot, as udev will not manage static device nodes that are created at runtime.
- Create a block device node if it does not exist yet. If suffixed with + and a file already exists where the device node is to be created, it will be removed and be replaced by the device node. It is recommended to suffix this entry with an exclamation mark to only create static device nodes at boot, as udev will not manage static device nodes that are created at runtime.
- Recursively copy a file or directory, if the destination files or directories do not exist yet. Note that this command will not descend into subdirectories if the destination directory already exists. Instead, the entire copy operation is skipped. If the argument is omitted, files from the source directory /usr/share/factory/ with the same name are copied. Does not follow symlinks.
- Ignore a path during cleaning. Use this type to exclude paths from clean-up as controlled with the Age parameter. Note that lines of this type do not influence the effect of r or R lines. Lines of this type accept shell-style globs in place of normal path names.
- Ignore a path during cleaning. Use this type to exclude paths from clean-up as controlled with the Age parameter. Unlike x, this parameter will not exclude the content if path is a directory, but only directory itself. Note that lines of this type do not influence the effect of r or R lines. Lines of this type accept shell-style globs in place of normal path names.
- Remove a file or directory if it exists. This may not be used to remove non-empty directories, use R for that. Lines of this type accept shell-style globs in place of normal path names. Does not follow symlinks.
- Recursively remove a path and all its subdirectories (if it is a directory). Lines of this type accept shell-style globs in place of normal path names. Does not follow symlinks.
- Adjust the access mode, group and user, and restore the SELinux security context of a file or directory, if it exists. Lines of this type accept shell-style globs in place of normal path names. Does not follow symlinks.
- Recursively set the access mode, group and user, and restore the SELinux security context of a file or directory if it exists, as well as of its subdirectories and the files contained therein (if applicable). Lines of this type accept shell-style globs in place of normal path names. Does not follow symlinks.
- Set extended attributes. Lines of this type accept shell-style globs in place of normal path names. This can be useful for setting SMACK labels. Does not follow symlinks.
- Recursively set extended attributes. Lines of this type accept shell-style globs in place of normal path names. This can be useful for setting SMACK labels. Does not follow symlinks.
Set file/directory attributes. Lines of this type accept shell-style globs in place of normal path names.
The format of the argument field is [+-=][aAcCdDeijsStTu] . The prefix + (the default one) causes the attribute(s) to be added; - causes the attribute(s) to be removed; = causes the attributes to be set exactly as the following letters. The letters "aAcCdDeijsStTu" select the new attributes for the files, see chattr(1) for further information.
Passing only = as argument resets all the file attributes listed above. It has to be pointed out that the = prefix limits itself to the attributes corresponding to the letters listed here. All other attributes will be left untouched. Does not follow symlinks.
- Recursively set file/directory attributes. Lines of this type accept shell-style globs in place of normal path names. Does not follow symlinks.
- Set POSIX ACLs (access control lists). If suffixed with +, the specified entries will be added to the existing set. systemd-tmpfiles will automatically add the required base entries for user and group based on the access mode of the file, unless base entries already exist or are explicitly specified. The mask will be added if not specified explicitly or already present. Lines of this type accept shell-style globs in place of normal path names. This can be useful for allowing additional access to certain files. Does not follow symlinks.
- Same as a and a+, but recursive. Does not follow symlinks.
If the exclamation mark is used, this line is only safe of execute during boot, and can break a running system. Lines without the exclamation mark are presumed to be safe to execute at any time, e.g. on package upgrades. systemd-tmpfiles will execute line with an exclamation mark only if option --boot is given.
# Make sure these are created by default so that nobody else can d /tmp/.X11-unix 1777 root root 10d # Unlink the X11 lock files r! /tmp/.X[0-9]*-lock
The second line in contrast to the first one would break a running system, and will only be executed with --boot.
The file system path specification supports simple specifier expansion. The following expansions are understood:
Table 1. Specifiers available
The machine ID of the running system, formatted as string. See machine-id(5) for more information.
The boot ID of the running system, formatted as string. See random(4) for more information.
The hostname of the running system.
Identical to uname -r output.
Single percent sign.
The file access mode to use when creating this file or directory. If omitted or when set to "-", the default is used: 0755 for directories, 0644 for all other file objects. For z, Z lines, if omitted or when set to "-", the file access mode will not be modified. This parameter is ignored for x, r, R, L, t, and a lines.
Optionally, if prefixed with "~", the access mode is masked based on the already set access bits for existing file or directories: if the existing file has all executable bits unset, all executable bits are removed from the new access mode, too. Similarly, if all read bits are removed from the old access mode, they will be removed from the new access mode too, and if all write bits are removed, they will be removed from the new access mode too. In addition, the sticky/SUID/SGID bit is removed unless applied to a directory. This functionality is particularly useful in conjunction with Z.
The user and group to use for this file or directory. This may either be a numeric user/group ID or a user or group name. If omitted or when set to "-", the default 0 (root) is used. For z and Z lines, when omitted or when set to "-", the file ownership will not be modified. These parameters are ignored for x, r, R, L, t, and a lines.
The date field, when set, is used to decide what files to delete when cleaning. If a file or directory is older than the current time minus the age field, it is deleted. The field format is a series of integers each followed by one of the following suffixes for the respective time units: s, m or min, h, d, w, ms, and us, meaning seconds, minutes, hours, days, weeks, milliseconds, and microseconds, respectively. Full names of the time units can be used too.
If multiple integers and units are specified, the time values are summed. If an integer is given without a unit, s is assumed.
When the age is set to zero, the files are cleaned unconditionally.
The age field only applies to lines starting with d, D, e, v, q, Q, C, x and X. If omitted or set to "-", no automatic clean-up is done.
If the age field starts with a tilde character "~", the clean-up is only applied to files and directories one level inside the directory specified, but not the files and directories immediately inside it.
For L lines determines the destination path of the symlink. For c and b, determines the major/minor of the device node, with major and minor formatted as integers, separated by ":", e.g. "1:3". For f, F, and w, the argument may be used to specify a short string that is written to the file, suffixed by a newline. For C, specifies the source file or directory. For t and T, determines extended attributes to be set. For a and A, determines ACL attributes to be set. For h and H, determines the file attributes to set. Ignored for all other lines.
Example 1. Create directories with specific mode and ownership
screen(1), needs two directories created at boot with specific modes and ownership:
# /usr/lib/tmpfiles.d/screen.conf d /run/screens 1777 root screen 10d d /run/uscreens 0755 root screen 10d12h
Contents of /run/screens and /run/uscreens will cleaned up after 10 and 10½ days, respectively.
Example 2. Create a directory with a SMACK attribute
D /run/cups - - - - t /run/cups - - - - security.SMACK64=printing user.attr-with-spaces="foo bar"
The directory will be owned by root and have default mode. Its contents are not subject to time based cleanup, but will be obliterated when systemd-tmpfiles --remove runs.
Example 3. Create a directory and prevent its contents from cleanup
abrt(1), needs a directory created at boot with specific mode and ownership and its content should be preserved from the automatic cleanup applied to the contents of /var/tmp:
# /usr/lib/tmpfiles.d/tmp.conf d /var/tmp 1777 root root 30d
# /usr/lib/tmpfiles.d/abrt.conf d /var/tmp/abrt 0755 abrt abrt -
Example 4. Apply clean up during boot and based on time
# /usr/lib/tmpfiles.d/dnf.conf r! /var/cache/dnf/*/*/download_lock.pid r! /var/cache/dnf/*/*/metadata_lock.pid r! /var/lib/dnf/rpmdb_lock.pid e /var/chache/dnf/ - - - 30d
The lock files will be removed during boot. Any files and directories in /var/chache/dnf/ will be removed after they have not been accessed in 30 days.
Example 5. Empty the contents of a cache directory on boot
# /usr/lib/tmpfiles.d/krb5rcache.conf e! /var/cache/krb5rcache - - - 0
Any files and subdirectories in /var/cache/krb5rcache/ will be removed on boot. The directory will not be created.