Type

The type consists of a single letter and optionally one or more modifier characters: a plus sign ("+"), exclamation mark ("!"), minus sign ("-"), equals sign ("="), tilde character ("~") and/or caret ("^").

The following line types are understood:

f, f+

w, w+

d

D

e

v

q

Q

p, p+

L, L+

c, c+

b, b+

C, C+

x

X

r

R

z

Z

t

T

h

H

a, a+

A, A+

Type Modifiers

If the exclamation mark ("!") is used, this line is only safe to 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(8) will take lines with an exclamation mark only into consideration, if the --boot option is given.

For example:

# 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.

If the minus sign ("-") is used, this line failing to run successfully during create (and only create) will not cause the execution of systemd-tmpfiles to return an error.

For example:

# Modify sysfs but don't fail if we are in a container with a read-only /proc
w- /proc/sys/vm/swappiness - - - - 10

If the equals sign ("=") is used, the file types of existing objects in the specified path are checked, and removed if they do not match. This includes any implicitly created parent directories (which can be either directories or directory symlinks). For example, if there is a FIFO in place of one of the parent path components it will be replaced with a directory.

If the tilde character ("~") is used, the argument (i.e. 6th) column is Base64 decoded[1] before use. This modifier is only supported on line types that can write file contents, i.e. f, f+, w, +. This is useful for writing arbitrary binary data (including newlines and NUL bytes) to files. Note that if this switch is used, the argument is not subject to specifier expansion, neither before nor after Base64 decoding.

If the caret character ("^") is used, the argument (i.e. 6th) column takes a service credential name to read the argument data from. See System and Service Credentials[2] for details about the credentials concept. This modifier is only supported on line types that can write file contents, i.e. f, f+, w, w+. This is useful for writing arbitrary files with contents sourced from elsewhere, including from VM or container managers further up. If the specified credential is not set for the systemd-tmpfiles service, the line is silently skipped. If "^" and "~" are combined Base64 decoding is applied to the credential contents.

Note that for all line types that result in creation of any kind of file node (i.e. f, d/D/v/q/Q, p, L, c/b and C) leading directories are implicitly created if needed, owned by root with an access mode of 0755. In order to create them with different modes or ownership make sure to add appropriate d lines.

Path

The file system path specification supports simple specifier expansion, see below. The path (after expansion) must be absolute.

Mode

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.

By default the access mode of listed inodes is set to the specified mode regardless if it is created anew, or already existed. Optionally, if prefixed with ":", the configured access mode is only applied when creating new inodes, and if the inode the line refers to already exists, its access mode is left in place unmodified.

User, Group

The user and group to use for this file or directory. This may either be a numeric ID or a user/group name. If omitted or when set to "-", the user and group of the user who invokes systemd-tmpfiles(8) 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, t, and a lines.

This field should generally only reference system users/groups, i.e. users/groups that are guaranteed to be resolvable during early boot. If this field references users/groups that only become resolveable during later boot (i.e. after NIS, LDAP or a similar networked directory service become available), execution of the operations declared by the line will likely fail. Also see Notes on Resolvability of User and Group Names[3] for more information on requirements on system user/group definitions.

By default the ownership of listed inodes is set to the specified user/group regardless if it is created anew, or already existed. Optionally, if prefixed with ":", the configured user/group information is only applied when creating new inodes, and if the inode the line refers to already exists, its user/group is left in place unmodified.

Age

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 "~", clean-up is only applied to files and directories one level inside the directory specified, but not the files and directories immediately inside it.

The age of a file system entry is determined from its last modification timestamp (mtime), its last access timestamp (atime), and (except for directories) its last status change timestamp (ctime). By default, any of these three (or two) values will prevent cleanup if it is more recent than the current time minus the age field. To restrict the deletion based on particular type of file timestamps, the age-by argument can be used.

The age-by argument overrides the timestamp types to be used for the age check. It can be specified by prefixing the age argument with a sequence of characters to specify the timestamp types and a colon (":"): "age-by...:cleanup-age". The argument can consist of a (A for directories), b (B for directories), c (C for directories), or m (M for directories). Those respectively indicate access, creation, last status change, and last modification time of a file system entry. The lower-case letter signifies that the given timestamp type should be considered for files, while the upper-case letter signifies that the given timestamp type should be considered for directories. See statx(2) file timestamp fields for more details about timestamp types.

If not specified, the age-by field defaults to abcmABM, i.e. by default all file timestamps are taken into consideration, with the exception of the last status change timestamp (ctime) for directories. This is because the aging logic itself will alter the ctime whenever it deletes a file inside it. To ensure that running the aging logic does not feed back into the next iteration of itself, ctime for directories is ignored by default.

For example:

# Files created and modified, and directories accessed more than
# an hour ago in "/tmp/foo/bar", are subject to time-based cleanup.
d /tmp/foo/bar - - - bmA:1h -

Note that while the aging algorithm is run an exclusive BSD file lock (see flock(2)) is taken on each directory/file the algorithm decides to remove. If the aging algorithm finds a lock (shared or exclusive) is already taken on some directory/file, it (and everything below it) is skipped. Applications may use this to temporarily exclude certain directory subtrees from the aging algorithm: the applications can take a BSD file lock themselves, and as long as they keep it aging of the directory/file and everything below it is disabled.

This behavior can be used to ensure guaranteed cleanup of files or directories whose lifetime should be aligned with the process that created them by having that process create them in a location monitored by systemd-tmpfiles with an age of "0", and having the process immediately lock the directory or file before using it. Because the BSD lock is process specific, the file is guaranteed to be unlocked as soon as the process exits, meaning that even if the process crashes, those files and directories will be unlocked and cleaned up by systemd-tmpfiles.

Argument

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 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.

This field can contain specifiers, see below.