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chmod command

Solaris UNIX Configure Disk Quota For UFS File System

How do I configure file system quotas to control how much available storage space can be used on a given UFS file system (such as /export/home) under Solaris UNIX operating systems?
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Linux / UNIX List User Dot-Files

How do I list only user dot-files from $HOME under UNIX and Linux operating systems? How do I ensure that user Dot-Files are not World-writable?
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SSH Authentication refused: bad ownership or modes for file /home/user/.ssh/authorized_keys2

I'm trying to login using ssh keys but server is only allows to login me using a password. The following message is logged into server /var/log/secure file:

Feb 25 06:36:50 ns5 sshd[26681]: Authentication refused: bad ownership or modes for file /home/user/.ssh/authorized_keys2

How do I fix this problem?
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Linux / UNIX Find All World-Writable Directories Have Sticky Bits Set

How do I find out all world writable directories have sticky bits set under CentOS Linux server?
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Linux Restrict Execution of /usr/sbin/userhelper to Console Users

I'm CentOS Linux version 5.x user and I'd like to restrict execution of /usr/sbin/userhelper to console users only in xusers group?
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Access Any Remote Server Port Without Modifying Firewall Settings

Q. I've couple of remote servers and I'd like to access few admin only application running on port 10000 and 3001. My firewall only allows port 80, 443, 25, 22 and 110 for public access. Do I need to open port 10000 and 3001 for everyone using firewall? How do I access my admin only apps without opening port 10000 and 3001?
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HowTo: Run the .sh File Shell Script In Linux / UNIX

I've downloaded a software for Linux from the Internet. There is a file called install.sh. How do I run an .sh file to install the software?
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Linux / UNIX Setup and Run PHP Script As A Cron Job

I've written a PHP script. I would like to run it as a cron job. I'm using CentOS server with Apache web server. How do I setup a PHP script as a cron job on a Linux or Unix-like systems?
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Chmod Numeric Permissions Notation UNIX / Linux Command

Can you provide more information about chmod command octal mode number notation?
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Howto: Linux Write protect a file

Q. How do I write protect a file under Linux? I’m using CentOS 5 server Linux operating system. I need prevent accidental changes to my files.

A. There are two ways to write protect a file under Linux.

Method #1: You can make file readonly by removing users’ write permission for a file. Under Linux and UNIX user cannot remove or modify file if they don’t have a write permission. You can use normal chmod command for this purpose.

Method #2 : You need to use chattr command which changes the file attributes on a Linux second extended (ext2 / ext3) file system. You need to setup 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. Only the superuser (root) or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute.

Write protecting a file using chmod command

Let say you want to write protect the file called data.txt so that no other users can change it, enter:
$ chmod go-w data.txt
To provide back permission use:
$ chmod go+w data.txt

Write protecting a file using chattr command

Let say you want to write protect the file called data.txt so that no other users can change it including root user, enter (you must login as the root user to use chattr command):
# chattr +i data.txt
To remove i attribute, enter:
# chattr -i data.txt