lsattr is the command that displays the attributes of a file.. Let's turn on the immutable attribute for the /etc/hosts file. You can recurse with find and call lsattr on one file at a time. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. That is "change attributes add immutable". : chmod can also set permissions using numbers. In the Python docs there is an article about the os interface which says that this method is available in Unix, but it doesn't work for Linux. The bottom line is this: if you have a variable that you intend to be immutable, check the syntax of the programming language youre using and take any specific steps needed to maintain that immutability if required. The chattr Man Page states the following: A file with the 'i' attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can be written to the file. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. In Silverblues case, its the operating system thats immutable. getgroups(2), :) But I would've fixed it myself if you'd left me a comment python get linux file immutable attribute, linuxquestions.org/questions/programming-9/, How terrifying is giving a conference talk? US Port of Entry would be LAX and destination is Boston. Treating r as 4, w as 2, and x as 1 is probably the easiest way to work out the numerical values for using chmod xxx filename, but there is also a binary method, where each permission has a binary number, and then that is in turn converted to a number. to change a permission from r-- to rw-, you still need to include r as well as w after the = in the chmod command invocation. rev2023.7.14.43533. Another environment? This avoids a certain amount of disk I/O for laptop systems. Why is that so many apps today require MacBook with a M1 chip? One cannot delete or modify file/folder once attributes are sets with chattr command, even though you have full permission. Linux/UNIX system programming training courses I've been in and around Open Source since around 1997, and have been running (GNU) Linux as my main desktop at home and work since then. Whether you use text or numbers will depend on personal preference and typing speed. Which field is more rigorous, mathematics or philosophy? coding(c, shell, php, python, java, javascript, nodejs, react); The group's permissions are set to r--, so the group has the ability to read the file but not write/edit it in any way it is essentially like setting something to read-only. When you want to restore a directory or file to default permissions e.g. capng_get_caps_fd(3), Perhaps the second one isn't finding any immutable files because there aren't any? | For instance, you could add a -v ORS='\0' to be able to feed it to GNU's xargs -r0. When a customer buys a product with a credit card, does the seller receive the money in installments or completely in one transaction? Why was there a second saw blade in the first grail challenge? %t min read You get a minimal OS image that includes only the tools needed to run containers, no package manager, and no configuration hassle. Not only is it difficult to compromise the core operating system as a standard user (as with many security issues, once you have sudo or root access, the situation is significantly degraded), but you are always operating in a known environment. Endless OS is a Linux distribution based on Debian. How to automatically log out an user in kde? However if you are changing the permissions to something out of the norm, it may be simpler and quicker to use the text method as opposed to trying to convert it to numbers, which may lead to a mistake. Your billing info has been updated. The new version only detects an 'i' in the attribute flags. # chattr -V +i geek.txt # Setting attribute to a file with -V chattr 1.41.12 (17-May-2010) Flags of geek.txt set as ---- i --------e- So we set attribute to the file geek.txt. If you are able to install the rawhide (rh) program (raf dot org slash rawhide), then immutable files can be found with: But this only works on Linux. chattr Example rev2023.7.14.43533. The problem at hand is more or less low-level, so let's go lower level: C++ is not that bad as a scripting language :) As a bonus, it has access to system C headers with full power of the C preprocessor. Many programming languages have the concept of "constants." To make the files immutable, "chattr" command can be used. Take a look at what are the options you have for an immutable Linux distribution. (Ep. Theres one key difference, however, which is that the operating system is mounted read-only, meaning that its immutable. Stack Exchange network consists of 182 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. But, recently, more projects are focusing on the immutability aspect as a core feature of the Linux distribution. capng_restore_state(3), cap_copy_ext(3), zfsonlinux doesn't support attributes at all at the moment) Share. How many witnesses testimony constitutes or transcends reasonable doubt? How would life, that thrives on the magic of trees, survive in an area with limited trees? File systems use permissions and attributes to regulate the level of interaction that system processes can have with files and directories. At this point, I'm afraid I'll have to write my own script to parse lsattr output for each directory. Connect and share knowledge within a single location that is structured and easy to search. To create one: Use getfattr to display extended attributes: Finally, to remove an extended attribute: To preserve extended attributes with text editors you need to configure them to truncate files on saving instead of using rename(2).[1]. 6 I'm using Python 2.7.9 under Debian GNU/Linux 8 (jessie) 64-bit. To change the owner of the mount location one can do the following: Before: drwxr-xr-x 5 root root 4096 Jul 6 16:01 Backup, After: drwxr-xr-x 5 archie root 4096 Jul 6 16:01 Backup. We should re-think our strategy and shift repositories from Windows repository servers towards Linux repositories. Archie can not do ls in the Documents directory but if they know the name of an existing file then they may list, rename, delete or (if the file's permissions allow it) access it. Once the file is set immutable, this file is impervious to change for any user. Also note that lsattr -R (at least 1.42.13) cannot report the flags of files whose path is larger than PATH_MAX (usually 4096), so someone could hide such an immutable file by moving its parent directory (or any of the path components that lead to it, except itself as it's immutable) into a very deep directory. I also like the fact that I can control what Im runningand what versionswith a great deal more ease than if I were on a standard operating system. NAME | DESCRIPTION | STANDARDS | NOTES | SEEALSO, Pages that refer to this page: Traditionally, immutable distributions existed to allow for easier testing and container-based software development. HTML rendering created 2023-06-24 If not, then root always has the ability change everything. The Linux Programming Interface. Even the root cannot modify, remove, overwrite, move or rename the file. getauxval(3), I need 700 permissions and . Now the partition can have data written to it by the new owner, archie, without altering the permissions (as the owner triad already had rwx permissions). lsattr /tmp/test.py Consider the following example, making a new partition with GParted for backup data. getpcaps(8), The description of the immutable attribute is best explained by the manual page for the chattr utility: # man chattr | grep -A1 "'i' attribute" A file with the 'i' attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can be written to the file. Connect and share knowledge within a single location that is structured and easy to search. What would be the correct command? Why is that so many apps today require MacBook with a M1 chip? e.g: After: -rw-rw-r-- 1 archie web 5120 Jun 27 08:28 foobar. To make a file immutable, use the chattr (change attribute) command to add the i attribute to the file: # chattr +i foo # date >> foo bash: foo: Permission denied # mv foo baz mv: cannot move \Qfoo' to \Qbaz': Operation not permitted # rm foo rm: cannot remove \Qfoo': Operation not permitted How to remove "System File" attribute from a file without command prompt? To make a file immutable, you can add immutable attribute to the file as follows. If you missed out r, it would take away the r permission as they are being re-written with the =. capng_set_rootid(3), Co-author uses ChatGPT for academic writing - is it ethical? root has rw access on all files at all times. mount_setattr(2), Success! Access control rules apply to the file attributes, while immutable is a filesystem extended file attribute, which may not be available on all filesystems. The first digit applies to permissions for owner, the second digit applies to permissions for group, and the third digit applies to permissions for all others. When this character is a space, there is no alternate access method. Deploy an application in Red Hat OpenShift on your laptop, How to install Red Hat OpenShift Local on your laptop, 8 open source 'Easter eggs' to have fun with your Linux terminal, article about Silverblue over at Enable Sysadmin, Download RHEL 9 at no charge through the Red Hat Developer program, A guide to installing applications on Linux, Linux system administration skills assessment, How well do you know Linux? to confirm the same you can use lsattr command. Though it might be a messy way of doing it, one way would be to determine if it is immutable by changing the file in some inconsequential way in a try except block, then reverting the change if it is not immutable. If there are additional attributes enabled around the immutable flag, then we'll not match them, and this will be fooled by files whose names happen to match the above pattern as well, such as this: We can tighten up the pattern a bit more like this: But it's still a bit too fragile and would require additional tweaking depending on the files within your filesystem. It'll be pretty slow though. Another example, denying write permissions to all (a): Before: -rw-rw-r-- 1 archie web 5120 Jun 27 08:28 foobar, After: -r--r--r-- 1 archie web 5120 Jun 27 08:28 foobar. Overall, MicroOS is a scalable, reliable, and secure option for server users. They can not list already existing files or create, rename, delete any of them. linux_desktop_user(true); The directory's contents cannot be shown. mount.fuse3(8), Knowability is very much a desirable property for security, as you can test, monitor, and perform forensic analysis from a known configuration. Is it legal to not accept cash as a brick and mortar establishment in France? statx(2), These are a few useful attributes. spufs(7), shmget(2), It only takes a minute to sign up. This will then work for situations such as this: But is imperfect. Proper way to declare custom exceptions in modern Python? If you put a 1 under each permission granted, and a 0 for every one not granted, the result would be something like this: You can then convert these binary numbers: The value of the above would therefore be 775. pam_systemd(8), Why *not* parse `ls` (and what to do instead)? Why was there a second saw blade in the first grail challenge? systemd-nspawn(1), - file: path: /tmp/null_p owner: foo group: bar mode: 0500 attr: i Above Adds immutable attribute to a file. sd_bus_creds_get_pid(3), Welcome back! libdrop_ambient(7), A community-built Linux distribution tailored for container workloads, as the name suggests. For details of in-depth However, it managed to make waves with its release, and then switching to a Debian base, ditching Ubuntu right after its first stable release. Posted: This basic structure of the code is this: Where xxx is a 3-digit number where each digit can be anything from 0 to 7. I wrote an article about Silverblue over at Enable Sysadmin, and over the weekend, I moved the laptop that one of my kids has over to it as well. Below is the command's general structure: Where who is any from a range of letters, each signifying who is being given the permission. Using + and - avoids this by adding or taking away from the current set of permissions). Why is that? setcap(8). Unlike any other Debian-based distro (say, Ubuntu), Endless OS features a robust design with immutability at its heart to ensure updating a package does not break the system. Unable to log in to any user accounts on a fresh install of Arch linux, Make file read only on Linux even for root, cannot touch file: No such file or directory for a specific file. Take note that only the superuser can set or clear this attribute. See chattr(1) for a complete list of attributes and for more info on what each attribute does. Hunt these 8 hidden or surprising features to make your Linux experience more entertaining. For config auditing reasons, I want to be able to search my ext3 filesystem for files which have the immutable attribute set (via chattr +i). 23. chattr +i sets the immutable filesystem attribute on the file. Let us look at another example, this time of a file, not a directory: Here we can see the first letter is not d but -. AFAIK, immutable is supported by all common linux filesystems (incl ext2/3/4 and xfs. spu_run(2), capng_change_id(3), Why does this journey to the moon take so long? It is a bit more convoluted, but here included for completeness. Connect and share knowledge within a single location that is structured and easy to search. systemd.nspawn(5), systemd.journal-fields(7), Making statements based on opinion; back them up with references or personal experience. Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. getcap(8), Why Extend Volume is Grayed Out in Server 2016? The directory's contents can be modified (create new files or directories; rename or delete existing files or directories); requires the execute permission to be also set, otherwise this permission has no effect. }, Linux: Get SSL Certificate Expiration Date, Creative Commons Attribution 4.0 International License. Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute. It takes a Flatpak-first and container-first approach. How do you update your system, then? never crosses mount points. (This method is not suitable for intrusion detection in cases where the root user may be compromised, but then neither is using the same system's lsattr utility which is also owned by the same root user.). blendOS is an interesting distro in development which aims to provide all the good things from other distributions. 1) This is a normal behaviour. Another image. Is this gap under my patio sidelights okay? Why did the subject of conversation between Gingerbread Man and Lord Farquaad suddenly change? Learn more about Stack Overflow the company, and our products. A single character that specifies whether an alternate access method applies to the file. killpg(3), read and write (and execute) permission to the owner but deny write permission to everyone else, it may be faster to use chmod 755/644 filename. In the next example, you want to grant read and execute permissions to the group, and other users, so you put the letters for the permissions (r and x) after the =, with no spaces. If this is to keep your kids from staying up on the computer too late, then perhaps try changing the root password and reduce the permissions granted by, How terrifying is giving a conference talk? unix(7), setpriv(1), I can use os.stat(pathname) to get pathname's perssmions, mtime, atime. fork(2), lsattr operates by issuing a FS_IOC_GETFLAGS ioctl syscall and retrieving the file's inode flags. UNIX is a registered trademark of The Open Group. capng_updatev(3), cap_init(3), I can't help it if you didn't read either the post or the command before running it. packet(7), netlink(7), syslog(2), This consideration brings us to two of the reasons that you should never run containers with root privilege. Using numbers is another method which allows you to edit the permissions for all three owner, group, and others at the same time, as well as the setuid, setgid, and sticky bits. Thanks to Ramesh, slm and Stphane for pointing me in the right direction (I was missing the -R switch for lsattr). Linux is a registered trademark of Linus Torvalds. Alternatively if you wanted everyone to only have read permission the number would be 444. What does the "yield" keyword do in Python? Here, because you want to deny permissions, you do not put any letters after the = where permissions would be entered. ld.so(8), To see this in action with examples consider the previous example that has been used but with this numerical method applied instead: If this were an executable the number would be 774 if you wanted to grant executable permission to the owner and group. while getting the immutability and update reliability as one would expect. shmop(2), prctl(2), Find centralized, trusted content and collaborate around the technologies you use most. Historical installed base figures for early lines of personal computer? Note that you cannot copy a set of permissions as well as grant new ones e.g. immutable - the "i" attribute makes a file immutable, which means that the file can't be modifed, renamed, or . In this number notation, the values r, w, and x have their own number value: To come up with a 3-digit number you need to consider what permissions you want owner, group, and all others to have, and then total their values up. Red Hat and the Red Hat logo are trademarks of Red Hat, Inc., registered in the United States and other countries. Warning: When used for security purposes, permissions and attributes only defend against attacks launched from the booted system. I'm not sure you're using the right ioctl here At least chattr and the solution of Setting Immutable Flag using ioctl() in C use FS_IOC_SETFLAGS (you can see what chattr does using strace). 589). A more permanent solution would require writing some C or something like Cython. carbonOS also aims to provide safe system updates, and verified boot as some features that not all atomic distros offer. Capabilities are a per-thread attribute. msgget(2), capng_update(3), capng_clear(3), systemd.unit(5), They can list the files and (if the file's permissions allow it) may access an existing file in Documents. I should have clarified that in my case, I'm auditing just for config management, not intrusion detection, so I don't have to worry too much about newlines, as I know the file names I'm working with won't have them. The permissions that all the other users have over the file, explained below. blendOS Aims to Replace All Linux Distributions. What is the difference between a standard airworthiness and a experimental airworthiness certificate? systemd.exec(5), core(5), Why does this journey to the moon take so long? Is this possible? Making statements based on opinion; back them up with references or personal experience. ptrace(2), You've successfully subscribed to It's FOSS. Probability Theory is Applied Measure Theory? Co-author uses ChatGPT for academic writing - is it ethical? carbonOS also aims to provide safe system updates, and verified boot as some features that not all atomic distros offer. So, you might want to go through its documentation to explore and get started. To search the apparent tree, crossing mount points as needed, remove FTW_MOUNT flag in the nftw call. Objective: Make a file undeletable or immutable on Linux. To remove the protection: chattr -i filename.ext. Any issues to be expected to with Port of Entry Process? arp(7), From xattr(7): "Extended attributes are name:value pairs associated permanently with files and directories". The Overflow #186: Do large language models know what theyre talking about? The use of immutable attributes on backup files on Linux repositories is a huge step forward towards backup security. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. Of course, you can change things if you would like to. 589). sched_setscheduler(2), NixOS is one of the most advanced Linux distributions available. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. For example, chmod 2777 filename will set read/write/executable bits for everyone and also enable the setgid bit. Gparted does this all as root so everything belongs to root by default. The user interface and the experience remains unchanged from a typical Fedora Workstation release. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Not all filesystems support every attribute. Probably not good for auditing as one can fake or hide an immutable file by have newline characters in the file name with that approach. Butand this depends on the language you are usingit may be that the constant is not immutable. :-). capng_name_to_capability(3), Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute. (Ep. This fact means that you have two levels of security provided as default when you run applications on a Silverblue system: the operating system's immutability, and the container's immutability. Check your inbox and click the link. -f Suppress most error messages. The immutable attribute has to be cleared before the file can be deleted. How to improve search time for searching files in a lot of directories, Linux search for a string only in a given set of files. You can always roll back to the previous version of the operating system if something goes wrong after an update. intro(3), Should I include high school teaching activities in an academic CV? cap_from_text(3), To use this flag every time, set it within an alias. To be more accurate, in a software context, it generally means that something cant be changed during run time. Fedora Silverblue aims to offer a stable experience which is useful for testing and container-based software development. File systems use permissions and attributes to regulate the level of interaction that system processes can have with files and directories. The only thing you can do with it is read it (if unix permissions allow) and (as root) chattr -i to remove the immutable bit. Instead, given how lightweight containers are, you should design your application in such a way that if you need to, you can just kill the container instance and replace it with an instance from an updated image. capng_apply_caps_fd(3), And, some options are still in their early phases of development. carbonOS: This Upcoming Independent Distro is All About UX and Robust Experience. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. It is one of the most popular immutable distributions out there. 589). A different shortcut is the special X mode: this is not an actual file mode, but it is often used in conjunction with the -R option to set the executable bit only for directories, and leave it unchanged for regular files, for example: It is possible to tell chmod to copy the permissions from one class, say the owner, and give those same permissions to group or even all. You can also use the numeric method to set the setuid, setgid, and sticky bits by using four digits. process_madvise(2), You need to run the command as a superuser in order to remove the immutable attribute. (Ep. This page was last edited on 18 November 2022, at 12:04. (Ep. It takes a Flatpak-first and container-first approach. It focuses on providing a seamless user experience with robust tech at its core. semget(2), You've successfully signed in. Fret not, if you do not know about NixOS, you can explore our NixOS series to learn and set it up. From our point of view, however, whats great about containers is that you can choose to use them immutably. You can easily launch a Talos cluster inside Docker too. Why did the subject of conversation between Gingerbread Man and Lord Farquaad suddenly change? Take note that only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this immutable attribute on Linux. Catch multiple exceptions in one line (except block). Only the superuser or a process possessing the execve(2), Perhaps someone with some reputation could comment or edit that answer (this is my first post)? For a complete list of all file attributes and flags, type man chattr in your terminal. This article was originally posted on Alice, Eve and Bob a security blog. Find centralized, trusted content and collaborate around the technologies you use most. uselib(2), How can I find all files containing specific text (string) on Linux? Conclusions from title-drafting and question-content assistance experiments How to set gid and uid in os.FileMode in golang? Capabilities(7) Miscellaneous Information Manual Capabilities(7), Linux man-pages 6.04 2023-03-17 Capabilities(7), https://archive.org/details/posix_1003.1e-990310, https://git.kernel.org/pub/scm/libs/libcap/libcap.git/refs/. If the filesystem UID is changed from nonzero to 0, then any of these capabilities that are enabled . A work around would be to use find with -execdir: Now, with -print0, that's post-processable, but if you intend to do anything with those paths, note that any system call on file paths greater than PATH_MAX would still fail and directory components could have be renamed in the interval. The goal is to make both of this files immutables, one way to do this is using sudo chattr +i file, what i am looking is a way of making the immutable attribute imposible to remove even for root ( sudo chattr -i file ). You can have a look at /usr/include/linux/fs.h, notably the big comment about "Inode flags", for more information. 173.236.169.23 setfsuid(2), A conditional block with unconditional intermediate code, Control two leds with only one PIC output. Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page. Some are configured to work on old computers, some aim to great user experience and some focus on security. pciconfig_read(2), Extended attributes: the good, the not so good, the bad. As a security guy, I approve of defense-in-depth, and this is a classic example of that property. Why can you not divide both sides of the equation, when working with exponential functions? capng_get_rootid(3), kill(2), Archie is only capable of (if the file's permissions allow it) accessing those files the Documents directory which they know of. A. Success! Super User is a question and answer site for computer enthusiasts and power users. To clear the immutable flasg, we will need to use the -i option. Geometric formulation of the subject of machine learning. How do I check whether a file exists without exceptions? The immutable attribute makes it so not even root can delete or modify the files, and it is affected using the chattr command. MSE of a regression obtianed from Least Squares.