---
name: "composefs-dump"
section: "5"
platform: "linux"
package: "composefs"
version: "1.0.8-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/composefs-dump"
---

# composefs-dump(5)

textual file format for composefs content

## NAME

composefs-dump - textual file format for composefs content

## DESCRIPTION

Both the *composefs-info* and the *mkcompose* commands support generation/consumptions of a textual descriptions of the contents of a composefs image. This can be used to inspect or modify an image, or to generate an image without having to have a local directory with the files in it.

The file format is very simple, with one file per line, first with a 11 fixed fields, followed by a variable number of extended attributes for the file. It is recommended, but not required to include a trailing newline for the last file.

Fields are separated by a single space, and lines by a single newline. Extended attributes further use '=' to separate key from value. Therefore all these characters, as well as non-printable characters are escaped in the fields ('=' only in xattr fields). Also, back-slashes have to be escaped as they are used as the escape mechanism.

Escapes are of the form \\xXY which escapes a single byte using two hex digits. For example \\x00 is the zero byte and \\xff is the 255 byte. Optionally, these custom escapes are suppored:

\**\\\\\**\
  :    backslash.

**\\n**\
  :    newline.

**\\r**\
  :    carriage return.

**\\t**\
  :    tab

Optional fields that are not set contain '-', and if a field actually has that particular value it is escaped.

The fixed fields on a line are (all numbers in base 10 unless otherwise specified):

- **PATH**

  The full, absolute path of the file in the image. Any directories used as prefix in the path must have been in the file before this line.

- **SIZE**

  The size of the file. This is ignored for directories.

- **MODE**

  The st\_mode stat field the file in octal, which includes both the\
    permissions and the file type.

  Additionally, if the file is a hardlink, then this field will\
    start with a single '@' character, and the payload field points\
    to the target file. Note that all other fields are typically\
    filled out for a hardlink as the target, but for generation\
    of a new file we ignore all the fields except the payload.

- **NLINK**

  The st\_nlink stat field.

- **UID**

  The owner uid.

- **GID**

  The owner gid.

- **RDEV**

  The st\_rdev stat field.

- **MTIME**

  The modification time in seconds and nanoseconds since the unix\
    epoch, separated by '.'. Note this is not a float, "1.1" means\
    one second and one nanosecond.

- **PAYLOAD**

  The payload of the file. For symbolic links this means the symlink targets. For regular files this is the relative pathname for the backing files. For hardlinks (see **MODE**), this is the path of another file in this file that this is a hardlink of.

- **CONTENT**

  Small files can inline the actual content in the composefs image. This contains an escaped version of the content. This must match the size specified in **SIZE**

- **DIGEST**

  A fs-verity digest for the file (only used for regular files, and not if *CONTENT* is set) that will be validated against backing files when used.

After the fixed fields comes the xattrs, escaped and space-separated in the form **KEY**=**VALUE**. Note that '=' must be escaped in **KEY**.

## EXAMPLE

```
/ 4096 40755 4 1000 1000 0 1695372970.944925700 - - - security.selinux=unconfined_u:object_r:unlabeled_t:s0\x00
/a\x20dir\x20w\x20space 27 40755 2 1000 1000 0 1694598852.869646118 - - - security.selinux=unconfined_u:object_r:unlabeled_t:s0\x00
/a-dir 45 40755 2 1000 1000 0 1674041780.601887980 - - - security.selinux=unconfined_u:object_r:unlabeled_t:s0\x00
/a-dir/a-file 259 100644 1 1000 1000 0 1695368732.385062094 35/d02f81325122d77ec1d11baba655bc9bf8a891ab26119a41c50fa03ddfb408 - 35d02f81325122d77ec1d11baba655bc9bf8a891ab26119a41c50fa03ddfb408 security.selinux=unconfined_u:object_r:unlabeled_t:s0\x00
/a-hardlink 259 @100644 1 1000 1000 0 1695368732.385062094 /a-dir/a-file - 35d02f81325122d77ec1d11baba655bc9bf8a891ab26119a41c50fa03ddfb408 security.selinux=unconfined_u:object_r:unlabeled_t:s0\x00
/inline.txt 10 100644 1 1000 1000 0 1697019909.446146440 - some-text\n - security.selinux=unconfined_u:object_r:unlabeled_t:s0\x00
```

## SEE ALSO

**[composefs-info(1)](/composefs-info/1.md)**, **[mkcomposefs(1)](/mkcomposefs/1.md)**

composefs upstream ⟨https://github.com/containers/composefs⟩