List of Important Unix/Linux Files and Their Permissions

A file system is a logical collection of files on a partition or disk. A partition is a container for information and can span an entire hard drive if desired.

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The permissions of a file are the first line of defense in the security of a Unix system. The basic building blocks of Unix/Linux permissions are the read, write, and execute permissions, which are described in the following table:

Permission	Applied to directory	Applied to other type of file
read (r)	Grants the capability to read the contents of the directory or subdirectories.	Grants the capability to view the file.
write (w)	Grants the capability to create, modify, or remove files or subdirectories.	Grants write permissions, allowing an authorized entity to modify the file, such as by adding text to a text file, or deleting the file.
execute (x)	Grants the capability to enter the directory.	Allows the user to “run” the program.

Like UNIX, Linux chooses to have a single hierarchical directory structure. Everything starts from the root directory, represented by /, and then expands into sub−directories instead of having so−called ‘drives’.

In the Windows environment, one may put one’s files almost anywhere: on C: drive, D: drive, E: drive etc. Such a file system is called a hierarchical structure and is managed by the programs themselves (program directories), not by the operating system.

On the other hand, Linux sorts directories descending from the root directory / according to their importance to the boot process.

Ensure the following files have been assigned proper permissions:

S.No.	Filename	User	Group	Permissions
1	/bin	root	root	drwxr-xr-x
2	/etc	root	root	drwxr-xr-x
3	/etc/aliases	root	root	-rw-r–r–
4	/etc/default/login	root	root	-rw——-
5	/etc/exports	root	root	-rw-r–r–
6	/etc/hosts	root	root	-rw-rw-r–
7	/etc/hosts.allow	root	root	-rw——-
8	/etc/hosts.deny	root	root	-rw——-
9	/etc/hosts.equiv	root	root	-rw——-
10	/etc/hosts.lpd	root	root	-rw——-
11	/etc/inetd.conf	root	root	-rw——-
12	/etc/issue	root	root	-rw-r–r–
13	/etc/login.access	root	root	-rw——-
14	/etc/login.conf	root	root	-rw——-
15	/etc/login.defs	root	root	-rw——-
16	/etc/motd	root	root	-rw-r–r–
17	/etc/mtab	root	root	-rw-r–r–
18	/etc/netgroup	root	root	-rw——-
19	/etc/passwd	root	root	-rw-r–r–
20	/etc/rc.d	root	root	drwx——
21	/etc/rc.local	root	root	-rw——-
22	/etc/rc.sysinit	root	root	-rw——-
23	/etc/sercuetty	root	root	-rw——-
24	/etc/security	root	root	-rw——-
25	/etc/services	root	root	-rw-r–r–
26	/etc/shadow	root	root	-r——–
27	/etc/ssh/ssh_host_key	root	root	-rw——-
28	/etc/ssh/sshd_config	root	root	-rw——-
29	/etc/ssh/ssh_host_dsa_key	root	root	-rw——-
30	/etc/ssh/ssh_host_key	root	root	-rw——-
31	/etc/ssh/ssh_host_rsa_key	root	root	-rw——-
32	/etc/ttys	root	root	-rw——-
33	/root	root	root	drwx——
34	/sbin	root	root	drwxr-xr-x
35	/tmp	root	root	drwxrwxrwt
36	/usr/bin	root	root	drwxr-xr-x
37	/usr/etc	root	root	drwxr-xr-x
38	/usr/sbin	root	root	drwxr-xr-x
39	/var/log	root	root	drwxr-xr-x
40	/var/log/authlog*	root	root	-rw——-
41	/var/log/boot*	root	root	-rw——-
42	/var/log/cron*	root	root	-rw——-
43	/var/log/dmesg	root	root	-rw——-
44	/var/log/lastlog	root	root	-rw——-
45	/var/log/maillog*	root	root	-rw——-
46	/var/log/messages*	root	root	-rw——-
47	/var/log/secure*	root	root	-rw——-
48	/var/log/spooler*	root	root	-rw——-
49	/var/log/syslog*	root	root	-rw——-
50	/var/log/utmp*	root	utmp	-rw-rw-r–
51	/var/log/wtmp*	root	utmp	-rw-rw-r–
52	/var/log/xferlog	root	root	-rw——-
53	/var/run	root	root	drwxr-xr-x
54	/var/run/*.pid	root user	root user	-rw-r–r–
55	/var/spool/cron	root	root	drwx——
56	/var/spool/cron/crontabs/root	root	root	-r——–
57	/var/spool/mail	root	mail	drwxrwxr-x
58	/var/spool/mail/*	user	user	-rw-rw—-
59	/var/tmp	root	root	drwxrwxrwt

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