NAME

mount-zip - Mount a ZIP archive as a FUSE filesystem.

SYNOPSIS

mount-zip [options] zip-file [mount-point]

DESCRIPTION

mount-zip is a tool allowing to open, explore and extract ZIP archives.

mount-zip mounts a ZIP archive as a read-only FUSE file system, which can then be explored and read by any application.

mount-zip aspires to be an excellent ZIP mounter. It starts quickly, uses little memory, decodes encrypted files, and provides on-the-go decompression and caching for maximum efficiency.

The mount point should be an empty directory. If the mount point doesn't exist yet, mount-zip creates it first. If no mount point is provided, mount-zip creates one in the same directory as the ZIP archive.

OPTIONS

--help -h : print help

--version : print version

--quiet -q : print fewer log messages

--verbose : print more log messages

--redact : redact file names from log messages

--force : mount ZIP even if password is wrong

--encoding=CHARSET : original encoding of file names

-o nospecials : hide special files (FIFOs, sockets, devices)

-o nosymlinks : hide symbolic links

-o nohardlinks : hide hard links

USAGE

Mount a ZIP archive:

$ mount-zip foobar.zip mnt

The mounted ZIP archive can be explored and read using any application:

$ tree mnt
mnt
└── foo

0 directories, 1 file

$ cat mnt/foo
bar

When finished, unmount the file system:

$ fusermount -u mnt

FEATURES

• Read-only view
• Instant mounting, even with big ZIP archives
• Compression methods: deflate, bzip2
• Encryption methods: AES and legacy ZIP encryption
• Asks for decryption password if necessary
• Detects file name encoding
• Converts file names to Unicode UTF-8
• Deduplicates files in case of name collisions
• Unpacks files when reading them (on-the-go decompression)
• Supports all file types, including named sockets, FIFOs, block and character devices, symbolic links and hard links
• Supports UNIX access modes and DOS file permissions
• Supports owner and group information (UID and GID)
• Supports relative and absolute paths
• Supports high precision time stamps
• Works on 32-bit and 64-bit devices
• Supports ZIP64 extensions, even on 32-bit devices:
  • Supports ZIP archives containing more than 65,535 files
  • Supports ZIP archives and files bigger than 4 GB
• Supports ZIP format extensions:
  • 000A PKWARE NTFS Extra Field: High-precision timestamps
  • 000D PKWARE UNIX Extra Field: File type
  • 5455 Extended Timestamp
  • 5855 Info-ZIP Unix Extra Field (type 1)
  • 7855 Info-ZIP Unix Extra Field (type 2)
  • 7875 Info-ZIP New Unix Extra Field: Variable-length UIDs and GIDs

File Name Encoding

mount-zip is fully Unicode compliant. It converts the file names stored in the ZIP archive from their original encoding to UTF-8.

In order to interpret these file names correctly, mount-zip needs to determine their original encoding. By default mount-zip tries to guess this encoding using the detection feature provided by the ICU library. It can automatically recognize the following encodings:

• UTF-8
• CP437
• Shift JIS
• Big5
• EUC-JP
• EUC-KR
• GB18030
• ISO-2022-CN
• ISO-2022-JP
• ISO-2022-KR
• KOI8-R

For example, when mounting a ZIP containing a Shift JIS-encoded file name, the encoding is correctly detected:

$ mount-zip sjis-filename.zip mnt

$ tree mnt
mnt
└── 新しいテキスト ドキュメント.txt

0 directories, 1 file

This system is not foolproof, and doesn't recognize a number of popular encodings. For example, when mounting a ZIP containing file names encoded in CP866, they are interpreted as CP437 and rendered as Mojibake:

$ mount-zip cp866.zip mnt

$ tree mnt
mnt
├── äáΓá
└── ÆѬßΓ«óδ⌐ ñ«¬π¼Ñ¡Γ.txt

0 directories, 2 files

In this case, the user needs to explicitly specify the original file name encoding using the -o encoding mount option:

$ mount-zip -o encoding=cp866 cp866.zip mnt

$ tree mnt
mnt
├── Дата
└── Текстовый документ.txt

0 directories, 2 files

Name Deduplication

In case of name collision, mount-zip adds a number to deduplicate the conflicting file name:

$ unzip -l file-dir-same-name.zip
  Length      Date    Time    Name
---------  ---------- -----   ----
       25  2021-10-29 14:22   pet/cat
       21  2021-10-29 14:22   pet
       30  2021-10-29 14:22   pet/cat/fish
        0  2021-10-29 14:22   pet/cat/fish/
       26  2021-10-29 14:22   pet/cat
       22  2021-10-29 14:22   pet
       31  2021-10-29 14:22   pet/cat/fish
---------                     -------
      155                     7 files

$ mount-zip file-dir-same-name.zip mnt

$ tree -F mnt
mnt
├── pet/
│   ├── cat/
│   │   ├── fish/
│   │   ├── fish (1)
│   │   └── fish (2)
│   ├── cat (1)
│   └── cat (2)
├── pet (1)
└── pet (2)

3 directories, 6 files

Directories are never renamed. If a file name is colliding with a directory name, the file is the one getting renamed.

Encrypted Archives

mount-zip supports encrypted ZIP archives. It understand both the legacy ZIP encryption scheme, and the more recent AES encryption schemes.

When mount-zip finds an encrypted file while mounting a ZIP archive, it asks for a password. If the given password doesn't allow to decrypt the file, then mount-zip refuses to mount the ZIP archive and returns an error:

$ unzip -l different-encryptions.zip
Archive:  different-encryptions.zip
  Length      Date    Time    Name
---------  ---------- -----   ----
       23  2020-08-28 15:22   ClearText.txt
       32  2020-08-28 15:23   Encrypted AES-128.txt
       32  2020-08-28 15:23   Encrypted AES-192.txt
       32  2020-08-28 15:23   Encrypted AES-256.txt
       34  2020-08-28 15:23   Encrypted ZipCrypto.txt
---------                     -------
      153                     5 files

$ mount-zip different-encryptions.zip mnt
Need password for File [1] '/Encrypted AES-128.txt'
Password > Got it!
Use the --force option to mount an encrypted ZIP with a wrong password
Cannot open File [1] '/Encrypted AES-128.txt': Wrong password provided

Providing the correct password allows mount-zip to mount the ZIP archive and decode the files:

$ mount-zip different-encryptions.zip mnt
Need password for File [1] '/Encrypted AES-128.txt'
Password > Got it!
Password is Ok

$ tree mnt
mnt
├── ClearText.txt
├── Encrypted AES-128.txt
├── Encrypted AES-192.txt
├── Encrypted AES-256.txt
└── Encrypted ZipCrypto.txt

0 directories, 5 files

$ md5sum mnt/*
7a542815e2c51837b3d8a8b2ebf36490  mnt/ClearText.txt
07c4edd2a55c9d5614457a21fb40aa56  mnt/Encrypted AES-128.txt
e48d57930ef96ff2ad45867202d3250d  mnt/Encrypted AES-192.txt
ca5e064a0835d186f2f6326f88a7078f  mnt/Encrypted AES-256.txt
275e8c5aed7e7ce2f32dd1e5e9ee4a5b  mnt/Encrypted ZipCrypto.txt

$ cat mnt/*
This is not encrypted.
This is encrypted with AES-128.
This is encrypted with AES-192.
This is encrypted with AES-256.
This is encrypted with ZipCrypto.

You can force mount-zip to mount an encrypted ZIP even without providing the right password by using the --force option:

$ mount-zip --force different-encryptions.zip mnt
Need password for File [1] '/Encrypted AES-128.txt'
Password > Got it!
Continuing despite wrong password because of --force option

In this case, the files can be listed, but trying to open an encrypted file for which the given password doesn't work results in an I/O error:

$ tree mnt
mnt
├── ClearText.txt
├── Encrypted AES-128.txt
├── Encrypted AES-192.txt
├── Encrypted AES-256.txt
└── Encrypted ZipCrypto.txt

0 directories, 5 files

$ md5sum mnt/*
7a542815e2c51837b3d8a8b2ebf36490  mnt/ClearText.txt
md5sum: 'mnt/Encrypted AES-128.txt': Input/output error
md5sum: 'mnt/Encrypted AES-192.txt': Input/output error
md5sum: 'mnt/Encrypted AES-256.txt': Input/output error
md5sum: 'mnt/Encrypted ZipCrypto.txt': Input/output error

$ cat mnt/*
This is not encrypted.
cat: 'mnt/Encrypted AES-128.txt': Input/output error
cat: 'mnt/Encrypted AES-192.txt': Input/output error
cat: 'mnt/Encrypted AES-256.txt': Input/output error
cat: 'mnt/Encrypted ZipCrypto.txt': Input/output error

For security reasons, mount-zip doesn't allow to specify the password on the command line. However, it is possible to pipe the password to mount-zip's standard input:

$ echo password | mount-zip different-encryptions.zip mnt
Need password for File [1] '/Encrypted AES-128.txt'
Password is Ok

Symbolic links

mount-zip shows symbolic links recorded in the ZIP archive:

$ mount-zip symlink.zip mnt

$ tree mnt
mnt
├── date
└── symlink -> ../tmp/date

Note that symbolic links can refer to files located outside the mounted ZIP archive. In some circumstances, these links could pose a security risk.

Symbolic links can be suppressed with the -o nosymlinks option:

$ mount-zip -o nosymlinks symlink.zip mnt
Skipped Symlink [1] '/symlink'

2021-10-28 20:05:01 laptop ~/mount-zip/tests/blackbox/data (intrusive)
$ tree mnt
mnt
└── date

0 directories, 1 file

Special Files

mount-zip shows special files (sockets, FIFOs or pipes, character and block devices) recorded in the ZIP archive:

$ mount-zip pkware-specials.zip mnt

$ ls -n mnt
brw-rw---- 1    0    6 8, 1 Aug  3  2019 block
crw--w---- 1    0    5 4, 0 Aug  3  2019 char
prw-r--r-- 1 1000 1000    0 Aug 15  2019 fifo
-rw-r--r-- 3 1000 1000   32 Aug  9  2019 regular
srw------- 1 1000 1000    0 Aug  3  2019 socket
lrwxrwxrwx 1 1000 1000    7 Aug  3  2019 symlink -> regular
lrwxrwxrwx 1 1000 1000    7 Aug 25  2019 symlink2 -> regular
-rw-r--r-- 3 1000 1000   32 Aug  9  2019 z-hardlink1
-rw-r--r-- 3 1000 1000   32 Aug  9  2019 z-hardlink2
brw-rw---- 1    0    6 8, 1 Aug  3  2019 z-hardlink-block
crw--w---- 1    0    5 4, 0 Aug  3  2019 z-hardlink-char
prw-r--r-- 1 1000 1000    0 Aug 15  2019 z-hardlink-fifo
srw------- 1 1000 1000    0 Aug  3  2019 z-hardlink-socket
lrwxrwxrwx 1 1000 1000    7 Aug  3  2019 z-hardlink-symlink -> regular

Special files can be suppressed with the -o nospecials option:

$ mount-zip -o nospecials pkware-specials.zip mnt
Skipped Block Device [0] '/block'
Skipped Character Device [1] '/char'
Skipped Pipe [2] '/fifo'
Skipped Socket [4] '/socket'
Skipped Block Device [7] '/z-hardlink-block'
Skipped Character Device [8] '/z-hardlink-char'
Skipped Pipe [9] '/z-hardlink-fifo'
Skipped Socket [10] '/z-hardlink-socket'

$ ls -n mnt
-rw-r--r-- 3 1000 1000 32 Aug  9  2019 regular
lrwxrwxrwx 1 1000 1000  7 Aug  3  2019 symlink -> regular
lrwxrwxrwx 1 1000 1000  7 Aug 25  2019 symlink2 -> regular
-rw-r--r-- 3 1000 1000 32 Aug  9  2019 z-hardlink1
-rw-r--r-- 3 1000 1000 32 Aug  9  2019 z-hardlink2
lrwxrwxrwx 1 1000 1000  7 Aug  3  2019 z-hardlink-symlink -> regular

Hard Links

mount-zip shows hard links recorded in the ZIP archive.

In this example, the three file entries 0regular, hlink1 and hlink2 point to the same inode number (2) and their reference count is 3:

$ mount-zip -o use_ino hlink-chain.zip mnt

$ ls -ni mnt
2 -rw-r----- 3 0 0 10 Aug 14  2019 0regular
2 -rw-r----- 3 0 0 10 Aug 14  2019 hlink1
2 -rw-r----- 3 0 0 10 Aug 14  2019 hlink2

$ md5sum mnt/*
e09c80c42fda55f9d992e59ca6b3307d  mnt/0regular
e09c80c42fda55f9d992e59ca6b3307d  mnt/hlink1
e09c80c42fda55f9d992e59ca6b3307d  mnt/hlink2

Some tools can use the inode number to detect duplicated hard links. In this example, du only counts the size of the inode (2) once, even though there are three file entries pointing to it, and only reports 10 bytes instead of 30 bytes:

$ du -b mnt
10      mnt

Duplicated hard links can be suppressed with the -o nohardlinks option:

$ mount-zip -o nohardlinks hlink-chain.zip mnt
Skipped File [1]: Hardlinks are ignored
Skipped File [2]: Hardlinks are ignored

$ ls -ni mnt
2 -rw-r----- 1 0 0 10 Aug 14  2019 0regular

File Permissions

mount-zip shows the Unix file permissions and ownership (UIDs and GIDs) as recorded in the ZIP archive:

$ mount-zip unix-perm.zip mnt

$ ls -n mnt
-rw-r----- 1 1000 1000 0 Jan  5  2014 640
-rw-r---w- 1 1000 1000 0 Jan  5  2014 642
-rw-rw-rw- 1 1000 1000 0 Jan  5  2014 666
-rwsrwsr-x 1 1000 1000 0 Jan  5  2014 6775
-rwxrwxrwx 1 1000 1000 0 Jan  5  2014 777

Note that these access permissions are not enforced by default. In this example, I am able to read the file 640 even though I don't own it and I don't have the read permission:

$ md5sum mnt/*
d41d8cd98f00b204e9800998ecf8427e  mnt/640
d41d8cd98f00b204e9800998ecf8427e  mnt/642
d41d8cd98f00b204e9800998ecf8427e  mnt/666
d41d8cd98f00b204e9800998ecf8427e  mnt/6775
d41d8cd98f00b204e9800998ecf8427e  mnt/777

To enforce the access permission check, use the -o default_permissions mount option:

$ mount-zip -o default_permissions unix-perm.zip mnt

$ md5sum mnt/*
md5sum: mnt/640: Permission denied
md5sum: mnt/642: Permission denied
d41d8cd98f00b204e9800998ecf8427e  mnt/666
d41d8cd98f00b204e9800998ecf8427e  mnt/6775
d41d8cd98f00b204e9800998ecf8427e  mnt/777

Absolute and Parent-Relative Paths

mount-zip supports absolute and parent-relative paths in file names. Absolute paths are displayed under the ROOT directory. For parent-relative paths, every .. is replaced by UP. Finally, ordinary relative paths are placed under the CUR directory:

$ unzip -l mixed-paths.zip
 Length      Date    Time   Name
--------  ---------- -----  ----
      49  2021-11-02 13:55  normal.txt
      29  2021-11-02 13:55  ../up-1.txt
      30  2021-11-02 13:55  ../../up-2.txt
      40  2021-11-02 13:55  /top.txt
      45  2021-11-02 13:55  /../over-the-top.txt
--------                    -------
     193                    5 files

$ mount-zip mixed-paths.zip mnt
mount-zip[2886935]: Bad file name: '/../over-the-top.txt'
mount-zip[2886935]: Skipped File [4]: Cannot normalize path

$ tree mnt
mnt
├── CUR
│   └── normal.txt
├── ROOT
│   └── top.txt
├── UP
│   └── up-1.txt
└── UPUP
    └── up-2.txt

4 directories, 4 files

Smart Caching

mount-zip only does the minimum amount of work required to serve the requested data. When reading a compressed file, mount-zip only decompresses enough data to serve the reading application. This is called lazy or on-the-go decompression.

Accessing the beginning of a big compressed file is therefore instantaneous:

$ mount-zip 'Big One.zip' mnt

$ ls -lh mnt/
-rw-rw-r-- 1 root root 6.4G Mar 26  2020 'Big One.txt'

$ time head -4 'mnt/Big One.txt'
We're going on a bear hunt.
We're going to catch a big one.
What a beautiful day!
We're not scared.

real    0m0.030s
user    0m0.015s
sys     0m0.014s

mount-zip generally avoids caching decompressed data. If you read a compressed file several times, it is getting decompressed each time:

$ dd if='mnt/Big One.txt' of=/dev/null status=progress
6777995272 bytes (6.8 GB, 6.3 GiB) copied, 24.9395 s, 272 MB/s

$ dd if='mnt/Big One.txt' of=/dev/null status=progress
6777995272 bytes (6.8 GB, 6.3 GiB) copied, 24.961 s, 272 MB/s

But mount-zip will start caching a file if it detects that this file is getting read in a non-sequential way (ie the reading application starts jumping to different positions of the file).

For example, tail jumps to the end of the file. The first time this happens, mount-zip decompresses the whole file and caches the decompressed data (in about 13 seconds in this instance):

$ time tail -1 'mnt/Big One.txt'
The End

real    0m12.631s
user    0m0.024s
sys     0m0.656s

A subsequent call to tail is instantaneous, because mount-zip has now cached the decompressed data:

$ time tail -1 'mnt/Big One.txt'
The End

real    0m0.032s
user    0m0.018s
sys     0m0.018s

Decompressed data is cached in a cache file located in the /tmp directory. This cache file is only created if necessary, and automatically deleted when the ZIP is unmounted.

If mount-zip cannot create the cache file, it will do its best caching data in memory.

PERFORMANCE

On small archives mount-zip has the same performance as commonly used virtual filesystems such as KIO, Gnome GVFS, mc vfs, unpackfs, avfs and fuse-j-zip. But on large archives containing many files, mount-zip is pretty quick.

For example on my laptop, a ZIP archive containing more than 70,000 files is mounted in half a second:

$ ls -lh linux-5.14.15.zip
-rw-r--r-- 1 fdegros primarygroup 231M Oct 28 15:48 linux-5.14.15.zip

$ time mount-zip linux-5.14.15.zip mnt

real    0m0.561s
user    0m0.344s
sys     0m0.212s

$ tree mnt
mnt
└── linux-5.14.15
    ├── arch
...

4817 directories, 72539 files

$ du -sh mnt
1.1G    mnt

The full contents of this mounted ZIP, totalling 1.1 GB, can be extracted with cp -R in 14 seconds:

$ time cp -R mnt out

real    0m13.810s
user    0m0.605s
sys     0m5.356s

For comparison, unzip extracts the contents of the same ZIP in 8.5 seconds:

$ time unzip -q -d out linux-5.14.15.zip

real    0m8.411s
user    0m6.067s
sys     0m2.270s

Mounting an 8-GB ZIP containing only a few files is instantaneous:

$ ls -lh bru.zip
-rw-r----- 1 fdegros primarygroup 7.9G Sep  2 22:37 bru.zip

$ time mount-zip bru.zip mnt

real    0m0.033s
user    0m0.018s
sys     0m0.011s

$ tree -h mnt
mnt
├── [2.0M]  bios
├── [ 25G]  disk
└── [ 64M]  tools

0 directories, 3 files

Decompressing and reading the 25-GB file from this mounted ZIP takes less than two minutes:

$ dd if=mnt/disk of=/dev/null status=progress
26843545600 bytes (27 GB, 25 GiB) copied, 104.586 s, 257 MB/s

There is no lag when opening and reading the file, and only a moderate amount of memory is used. The file is getting lazily decompressed by mount-zip as it is getting read by the dd program.

LOG MESSAGES

mount-zip records log messages into /var/log/user.log. They can help troubleshooting issues, especially if you are facing I/O errors when reading files from the mounted ZIP.

To read mount-zip's log messages:

$ grep mount-zip /var/log/user.log | less -S

To follow mount-zip's log messages are they are being written:

$ tail -F /var/log/user.log | grep mount-zip

By default, mount-zip writes INFO and ERROR messages. You can decrease the logging level to just ERROR messages with the --quiet option. Or you can increase the logging level to include DEBUG messages with the --verbose option:

$ mount-zip -f --verbose foobar.zip mnt
Indexing 'foobar.zip'...
Allocating 16 buckets
Detected encoding UTF-8 with 15% confidence
Indexed 'foobar.zip' in 0 ms
Mounted 'foobar.zip' on 'mnt' in 2 ms
Reader 1: Opened File [0]
Reader 1: Closed
Unmounting 'foobar.zip' from 'mnt'...
Unmounted 'foobar.zip' in 0 ms

To prevent file names from being recorded in mount-zip's log messages, use the --redact option:

$ mount-zip -f --verbose --redact bad-crc.zip mnt
Indexing (redacted)...
Allocating 16 buckets
Indexed (redacted) in 0 ms
Mounted (redacted) on (redacted) in 2 ms
Reader 1: Opened File [0]
Cannot read (redacted): Cannot read file: CRC error
Reader 1: Closed
Unmounting (redacted) from (redacted)...
Unmounted (redacted) in 0 ms

RETURN VALUE

mount-zip returns distinct error codes for different error conditions related the ZIP archive itself:

0 : Success.

1 : Generic error code for: missing argument, unknown option, unknown file name encoding, mount point cannot be created, mount point is not empty, etc.

11 : The archive is a multipart ZIP.

15 : mount-zip cannot read the ZIP archive.

19 : mount-zip cannot find the ZIP archive.

21 : mount-zip cannot open the ZIP archive.

23 : Zlib data error. This is probably the sign of a wrong password. Use --force to bypass the password verification.

29 : The archive is not recognized as a valid ZIP.

31 : The ZIP archive has an inconsistent structure.

36 : The ZIP archive contains an encrypted file, but no password was provided. Use --force to bypass the password verification.

37 : The ZIP archive contains an encrypted file, and the provided password does not allow to decrypt it. Use --force to bypass the password verification.

PROJECT HISTORY

mount-zip started as a fork of fuse-zip.

The original fuse-zip project was created in 2008 by Alexander Galanin and is available on Bitbucket.

The mount-zip project was then forked from fuse-zip in 2021 and further developed by François Degros. The ability to write and modify ZIP archives has been removed, but a number of optimisations and features have been added:

AUTHORS

• François Degros
• Alexander Galanin

LICENSE

mount-zip is released under the GNU General Public License Version 3 or later.

SEE ALSO

fusermount(1), fuse(8), umount(8)