Where exactly is the journal on the EXT3/EXT4 file system, ive searched around and cant find a good answer.
To the best of my knowledge, it is a regular file controlled by an inode, but the inode does not have a directory entry. If you do tune2fs -l /dev/$ext3partition it will mention the "Journal inode" -- usually it seems to be number 8. You should be able to use debugfs to get more details.
Journal is the file located on the root directory with the name .journal or something like that. Just enable the journalling for your filesystem using the tune2fs and see the root directory. It will be a hidden file.
Related
I've been searching Google as well as the OpenVMS System Administrator's Guide and User Guide, and still can't find anything regarding listing the directories present on an OpenVMS volume. I can't see how this could taken for granted in the docs, since everything else is very specific, so either I'm failing to see it or it can't be done. If it can't be done, then I'm missing some incredibly large chunk of the picture in regards to using VMS. Any suggestions are appreciated.
TIA,
grobe0ba
By "listing", I assume you mean via a command such as Dir...
To see all directories on a volume I would do something like,
$ dir volumeid:[000000...]*.dir
Of course, you need enough privilege to be able to see all the directories on the volume.
For a quick overview of all the directories you may also check out the /TOTAL option for 'directory'.
$ DIRE /TOTAL [*...]
Add /SIZE for effect (and slowdown)
You can of course post process to your hearts content...
$ pipe dir /total data:[*...] | perl -ne "print if /^Dir/"
Directory DATA:[CDC]
Directory DATA:[CDC.ALPHA]
Directory DATA:[CDC.ALPHA.V8_3]
$ pipe dir /total data:[*...] | searc sys$pipe "ory "
Directory DATA:[CDC]
Directory DATA:[CDC.ALPHA]
Directory DATA:[CDC.ALPHA.V8_3]
$ pipe dir /total data:[*...] | perl -ne "chomp; $x=$1 if /^Di.* (\S+)/; printf qq(%-60s%-19s\n),$x,$_ if /Tot/"
DATA:[CDC] Total of 7 files.
DATA:[CDC.ALPHA] Total of 1 file.
DATA:[CDC.ALPHA.V8_3] Total of 11 files.
Finally, if you are serious about playing with files and directories on OpenVMS, be sure to google for DFU OPENVMS ... download and enjoy.
Unfortunately I do not have the reputation required for commenting so I have to reformulate the answer.
#ChrisB
This answer while voted is not correct generally speaking. Directories are always files ending with .DIR and having a version of 1. Renaming a directory to *.DIR;x with x>1 will render the directory not traverseval. The DIR file however retains its directory characteristics and renaming it back to ;1 will return its normal behavior.
So one may add a ;1 to the DIR command
$ dir volumeid:[000000...]*.dir;1
But again this is not valid because any one may create *.DIR files which are not directories (ex. EDIT TEST.DIR), and there are applications out there doing so.
#Hein
So the second answer from Hein, which at this time does have 0 votes, is the corretc one. The one that does exactely the requested operation without 3rd party tool is:
$ PIPE DIR /TOTAL volume:[*...] | SEARCH SYS$PIPE "ory "
This command will only show valid directories
In my program, I have to make a file hidden in order to avoid removal or modification of the file.
PATH=/etc/
NAME = file
Is there a function in C that will allow me to do that?
You can just add a . to the front of the file name. Having said that if your goal is to not allow modification of the file change the permissions to something that can't be modified. Something like:
chmod 444 fileName
First: others argue with security arguments here. For those: Hidden files have nothing to do with security nor will it prevent somebody from deleting a file if he has propper permission and wants to do that.
Hidden means only that tools like ls, bash globs or a graphical file managers will not display the files with their default settings. This can be useful to prevent from accidents (see explanation below) or just to keep directory listings more clean. You may try the commands ls -l $HOME and ls -al $HOME in order to see the differences.
On GNU/Linux systems and UNIXs it is by convention that files which's name begins with a dot . will not being displayed by default meaning they are hidden. Like $HOME/.bashrc
Solution: Prefix the file name with a dot:
.file
About accidents. Hiding a file can prevent you from accidently removing it when you type something like:
rm *
The glob above will not list hidden files so they won't get deleted.
In LINUX Hidden file are start with .(DOT)
if you create files with starting .(DOT), those files are hidden.
You can use chmod to set permissions to the file.
if you set only read only then those cannot be modified in program
chmod 444 filename
if you want to use this from C-language use system() function to execute this command
if You use simple ls -alF you can see those files.
the below files are hidden files In LINUX
-rw------- 1 root root 27671 Sep 17 11:40 .bash_history
-rw-r--r-- 1 root root 3512 Jul 23 16:30 .bashrc
There are no hidden files on Linux. Some tools don't show files starting with . as others already mentioned.
Anyway, you can experiment with putting control characters like new-line into the filename. See Control characters in filenames are a terrible idea:
Some control characters, particularly the escape (ESC) character, can cause all sorts of display problems, including security problems. Terminals (like xterm, gnome-terminal, the Linux console, etc.) implement control sequences. Most software developers don’t understand that merely displaying filenames can cause security problems if they can contain control characters. The GNU ls program tries to protect users from this effect by default (see the -N option), but many people display filenames without getting filtered by ls — and the problem returns. H. D. Moore’s “Terminal Emulator Security Issues” (2003) summarizes some of the security issues; modern terminal emulators try to disable the most dangerous ones, but they can still cause trouble. A filename with embedded control characters can (when displayed) cause function keys to be renamed, set X atoms, change displays in misleading ways, and so on. To counter this, some programs modify control characters (such as find and ls) — making it even harder to correctly handle files with such names.
Your requirements are a bit vague: the program creates a file, wants to prevent its removal or modification. Do you expect other users (of your program? in general?) to be able to read it, but not find it easily, or modify or delete it?
Keep in mind that Unix-like systems don't really do hidden when the resource involved needs to remain visible (readable, presumably), as others have noted. Prepending a '.' to a file name helps in some important contexts (default ls(1) behavior and shell * globbing in particular) but only goes so far. But a few techniques might help obscure what and where your app is saving things, if that matters.
Consider two users doing some shell commands like the following in a directory with its sticky bit set (say /tmp). (Sorry to not write C, but I think the scenario is easier to demonstrate out in the shell.)
As Bob:
$ umask 066
$ mkdir /tmp/.hidden
$ umask 022
$ echo xyzzy > /tmp/.hidden/mysecret.txt
$ ls -la /tmp/.hidden
total 28
drwx--x--x 2 bob users 4096 Sep 17 11:19 .
drwxrwxrwt 27 root root 20480 Sep 17 11:26 ..
-rw-r--r-- 1 bob users 6 Sep 17 11:19 mysecret.txt
As Alice. Notice that attempts to search in /tmp/.hidden fail, but if she knows the name of a file in a directory with only execute but not read permissions set, she can read the file. She can't do much to mess with /tmp/.hidden, once it's properly created. If she'd been forced to guess the name of the secret file, that could also be a challenge depending on how the name is created.
$ ls /tmp | grep hidden
$ ls -a /tmp | grep hidden
.hidden
$ file /tmp/.hidden
/tmp/.hidden: directory
$ ls /tmp/.hidden
ls: cannot open directory /tmp/.hidden: Permission denied
$ echo /tmp/.hidden/*
/tmp/.hidden/*
$ file /tmp/.hidden/mysecret.txt
/tmp/.hidden/mysecret.txt: ASCII text
$ cat /tmp/.hidden/mysecret.txt
xyzzy
$ rm -f /tmp/.hidden/mysecret.txt
rm: cannot remove '/tmp/.hidden/mysecret.txt': Permission denied
$ mv /tmp/.hidden /tmp/Hidden_No_More
mv: cannot move '/tmp/.hidden' to '/tmp/Hidden_No_More': Operation not permitted
$ rm -rf /tmp/.hidden
rm: cannot remove '/tmp/.hidden': Permission denied
In this scenario, the presence of the hidden directory can be obscured, but ls -a reveals its name. Carefully chosen directory permissions prevent non-root and non-Bob users from listing or altering its contents. The use of a sticky-bit directory like /tmp prevents non-Bobs from renaming or removing the "hidden" directory. Anyone who knows the name of the "secret" file within the hidden directory can read it. But only Bob and root can change these "secret" files or the "hidden" directory.
You can do all the above in a C program; equivalents exist as library and system calls - see things like chmod(2), mkdtemp(3), umask(2), the mode argument to open(2), etc.
If you use a kernel >= 3.11, you might want to try the O_TMPFILE-flag. This kernel have been released on the 14.09.2013. Debian Jessie uses Kernel 3.16. so this feature should be available on all recent popular distributions.
The news about this sounds promising. The file will be unreachable from the outside. No other process or may access this file .. neither read nor write. But the file will be lost as soon as the handle gets closed. Or link it to a regular file. But then, it will be accessible as any other file.
If this is not an option for you (e.g. your file needs to be persistent): bad luck. There is no real "hidden" file in linux. You can hide your persistent files as secure as files on windows with the hidden attribute: prepend the name with a dot. As stated by others: ls -a will show them nevertheless.
Also, you can create a user specifically for your use and make the file read- and writable only for this user or put it in a folder, where only your user have rw-access. Other users may see this file but wont be able to access it. But if root comes along and want to look into it, you have lost.
Sure,you have to add '.' before filename and your file wouldn't be seen by user(except user will turn the hidden files show option on). You could change the attrybutes (chmod) to 755 and only user could rwx and others could rx.
hek2mgl - partially yes - it has. Try to remove via rm -rf * manner all of directory content. That's why for example .htaccess is hidden.
The documentation says that all files moved to trash are stored normally in ~/.local/share/Trash/files. Are there an exception for files removed from removable media? Are they stored in drive_root/.Trash-xxx directory? Or is this behavior obsolete?
How do I find real file path of file in trash can? I have a list of GFileInfo obtained from g_file_enumerate_children for trash:/// uri. It's easy if all files are stored in one directory. But I'm afraid this could be different for removable drives.
From removeable media there are the .Trash-$(user_id) folders, so you will have to get all mounted disks as well as the home trashcan.
Under each mounted device (not being the home folder) will be a .Trash folder for each user ever having something deleted. So e.g. for my user foo which has ID 1000 (see /etc/passwd) you will have to look for .Trash-1000 folders.
This is AFAIK not obsolete, just think about the oposite, the file would have to be copied over to your home storage just to move it to trash...
For the second part, you probably better off asking that on the glib/gtk mailinglist.
Can ctags tag symbols from a directory up in the hierarchy also or is it limited to create tags for current and sub-directories only?
Basically I'm looking for Visual Studio like symbol cross referencing it is very helpful in understanding alien source code flow.
If not Vim, then which other editor should I use?
thanks
Ctags only recurses to subdirectories. But all you have to do is run ctags -R . in your project home directory, and it will create a tags file for your whole project.
You aren't limited to specifying one tags file in Vim. This is an alternative to the other answers; you can just do something like:
set tags=tags,~/wintags,c:/path/to/moretags/etc
So you don't need to take the time regenerating a monolithic tags file when you just want to update your local tags.
Regarding the OP's comment in another answer,
yes thats correct but when i open a file say proj/dir1/def.c and press ctrl+] on a function name which is defined say in proj/dir2/abc.c, I get tag not found :(
You could also create one tags file for all of your projects at the 'proj' root:
set tags=tags;c:/path/to/proj
This will use the first file named tags that it finds as it walks up the directory hierarchy from where you are.
You can combine these two techniques to have a project-local tags file and then a "global" tags file that isn't updated as often.
Whilst it's got similar user interface for asking it to do it's thing, so you need to actually specify "go down directories", I find that cscope is a very nice tool, whcih does everything that ctags does and a bit more.
ctags (well, exctags at least) can create tags for as many directory trees you want. Simply run
exctags -R dir1 dir2 ...
Then vim knows about all the symbols you need. For example, one of the directories could be /usr/include in addition to your own source directory.
Make sure to run vim path/to/file.c from the same directory you created the tags file in.
In our FreeBSD-environment where we have one server that acts as a file-server, we have a problem that our system administrator says can not be fixed.
All our files resides in a directory and we all have access to that directory, its sub-directories and files. The problem is that once a user in our group creates a file or directory, we have to chmod that directory or file to change the rights so that others in our group can access, read, write and delete. These are not files or sub-directories inside our home-directories, but in a directory where we are supposed to work with them on a daily basis.
Finding it difficult to believe that there is no good solution, I would request that someone assist me with a solution.
I think what you want is a setgid bit on the directories and umask. Then newly created there files and directories will have proper group and proper permissions to let others read abd write them.
find /your-files-are-rooted-here -type d -print0 | xargs -0 chmod ug+rw,g+s
and set umask to 002 (or whatever is appropriate). And, of course, you may want to fix permissions for existing files (the command above only takes care of directories).
One place to but the umask setting is "/etc/bashrc". Find "umask". Change "umask = 022" to "umask = 002". After doing this, when a new file created, every one in the same group with the file owner can write in this new file.
Note that this only works for files created from the shell, specifically bash.