e2fsimage(1)

📦 version 0.2.3, in alpine 3.24

💅 e2fsimage — from the General Commands Manual files, bestie 💖

okay so picture this: you wanna make an ext2 filesystem image, and you do not have root. iconic. that's literally this tool. let's get into it ✨

✨ NAME ✨

e2fsimage — create and populate an ext2 filesystem image as non-root user 🫶

🎀 SYNOPSIS 🎀

e2fsimage [-t fs-type] [-b block-size] [-L volume-label] [-f imgfile]
[-d rootdir] [-u uid] [-g gid] [-D file] [-U file] [-P file] [-p] [-v]
[-S] [-n] [-s size]

🌸 DESCRIPTION 🌸

So e2fsimage does the thing where it creates an ext2 filesystem image by recursively copying the files from your existing directory structure, rootdir, over into the image-file. very demure, very mindful 💅

The filetypes it supports are: regular files, directorys, hard-links, softlinks, block special devices, character special devices and fifos. (yes "directorys" — we keep the typo, it's part of the lore ✨)

Hard links get resolved so they come out as actual hard links inside the image 🔥. The content (target) of softlinks is copied “ as-is ” and will not be resolved or altered in any way — not even a little, no cap.

The usual way to create ext2 filesystem images for initial ramdisks, boot-floppys or bootable CDs is to create an image with, eg.:

1    dd if=/dev/zero of=e2img bs=1024 count=4096
2    mke2fs -F e2img
3    mount -o loop e2img mounpoint
4    cp -r rootdir/* mountpoint
💀 heads up bestie: at least the last 2 commands must be executed as root. Also, to set the different ownerships (usually root) and to create the special device files, root permissions are needed too. so like… yeah.

Since all this results in a file that may belong to an ordinary user, this file can be created and filled with the filesystem structure by her 🌈. This application manages to create such an image as ordinary user without sudo or the suid-root bit set. Of course suid-root programs in the filesystem image are possible by making them suid-user — when this files are copied, the user is set to root, and there you have your suid-root program 👑. It is also not mandatory to have the rootdir on an ext2 filesystem. slay.

⭐ OPTIONS ⭐

  • -t fs-type — Specify the filesystem type (i.e., ext2, ext3, ext4, etc.) that is to be created. See mke2fs(2).
  • -b block-size — Specify the size of blocks in bytes. Valid block-size values are 1024, 2048 and 4096 bytes per block. See mke2fs(2).
  • -L volume-label — Set the volume label for the filesystem to volume-label. The maximum length of the volume label is 16 bytes.
  • -d rootdir — The content of the filesystemimage is a recursive copy of rootdir. All files are copied while preserving all attributes but the uid/gid. They will usually be set to root.root. This can be overwritten with the -u and -g options respectively.
  • -e pattern — Exclude files based upon pattern.
  • -D devicefile — The devicefile contains all special devices to be created, see DEVICES. The default filename is .DEVICES.
  • -U uidgidfile — The uidgidfile contains the uids and gids different from 0, see USERS. The default filename is .UIDGID.
  • -P passwd — The password file in this parameter is used to convert user names to uids and gids. It tries to use the default in rootdir/etc/passwd, if it is omitted.
  • -G group — The group file in this parameter is used to convert group names to gids. It tries to use the default in rootdir/etc/group, if it is omitted.
  • -f imgfile — This is the target file for the filesystem image. An existing file will be overwritten as long as -n is not given. 🙈
  • -g gid — Change the default group id from 0 to gid. Until now there is only 1 gid for all files supported. If you need different gids for different files, take a look at USERS.
  • -n — This option allows to reuse an existing filesystem image defined by -f. The existing content is not modified by any means but there may not exist a file with the same name as a newly created one.
  • -p — Preserve original file owner. If this option is omitted all files in the image will belong to root. (This is usually what you want 😌)
  • -s size — When the filesystem is created the size will be size Kbytes large. The default is 4096 kilo bytes.
  • -u uid — Change the default user-id from 0 to uid. Until now there is only 1 uid for all files supported. If you need different uids look at the section USERS.
  • -v — Be more verbose. 🗣️
  • -S — Skip unaccessible files and dirs.

🦋 DEVICES 🦋

Usually the devices are created using mknod by root. Obviously this would absurd the existence of e2fsimage to be a non-root tool 🫠. So: a device special file called .DEVICES can be placed in every directory (usually dev) that will contain device special files. The format of this file is:

<name> <type> <major> <minor> [ <mode> [ <uid> [ <gid> ]]]
  • name — the name of the file like ttyS0
  • type — Actually supported are c,u for character special devices, b for block special devices and p,f for fifos.
  • major minor. — This are the major and minor numbers of the device
  • mode — The access mode for the file like 0644. The default mode for devices is 0600 if mode is omitted.
  • uid — The uid of the device, 0 if omitted.
  • gid — The gid of the device, 0 if omitted.

A call to mknod like mknod -m 0600 ttyS1 c 4 65 would result in a line in dev/.DEVICES as "ttyS1 c 4 65 0600" ✨

💜 USERS 💜

Every directory may contain a file named .UIDGID. This filename can be changed by using the -U option. The format of this file is:

<name> <uid> [ <gid> ]

<name> <username> [ <groupname> ]

If <name> is ".", then the owner and group information will be kept recursively for all files and directorys below. For a chown 500 /home/user one would write "user 500" to "home/.UIDGID and have such a directory "home/user" of course. For a chown -R 500 /home/user one would write a ". 500" to "home/user/.UIDGID". Userid information given in .UIDGID overrides user info in .DEVICES 👑

If the uid entry is not numeric it will be resolved by using passwd, provided by the option -P. In this case the gid is also taken from passwd, if the groupname is omitted. If the groupname is provided, the group file from -G is used to resolve the gid.

  • name — is the name of the file.
  • uid — is the numeric userid of the file.
  • gid — is the numeric groupid of the file. It will be zero if omitted.
  • username — is the user name of the file owner, resolved by passwd.
  • groupname — is the group name of the file, resolved by group.

💀 BUGS 💀

Bugs ? 😭 (that's it. that's the whole section. we respect the mystery.)

🌈 SEE ALSO 🌈

mke2fs(8)

👑 AUTHOR 👑

This program was written by Christian Hohnstaedt <christian@hohnstaedt.de> The project homepage is http://www.hohnstaedt.de/e2fsimage

okay that's the whole thing, bestie, you're basically a filesystem witch now 🧚💖

version 0.2.3 of the e2fsimage(1) page — that's the one you just read, go forth and image those filesystems 🍓✨

📦 where this page comes from