In RHEL 5, you can simply install the ftp server package using the following steps without modifying anything in the configuration file, and then you can logon to the ftp server with any user account in your system. If you want to add more control to your vsftp server, modify the configuration files under the […]
Archives for September 2017
CentOS / RHEL 5 : dm-multipath file /etc/sysconfig/mkinitrd/multipath explained
– The purpose of the /etc/sysconfig/mkinitrd/multipath file, is to help mkinitrd determine whether or not to include the dm-multipath modules in the initrd image file. – Note that setting MULTIPATH=yes has no effect, unless mkinitrd detects that the root device is using multipath. Remember that the purpose of the initrd image is only to load […]
CentOS / RHEL 5 : How to disable device mapper multipath (dm-multipath)
In CentoS/ RHEL 5, the device mapper multipath is installed by default. In order to avoid any conflict with third party multipath software, it is advised to disable the native RHEL device-mapper-multipath software. Follow the steps below to disable the dm-multipath in RHEL 5 systems. Disabling dm-multipath 1. To disable device-mapper-multipath, turn it off with […]
/proc/cpuinfo file explained
The file /proc/cpuinfo displays what type of processor your system is running including the number of CPUs present. Here is an example output from cat /proc/cpuinfo of a system. # cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 45 model name : Intel(R) Xeon(R) CPU E5-2660 0 @ 2.20GHz […]
Linux OS service ‘nfs’
Service Name nfs Description The Network File System (NFS) is a server/client based networking protocol. NFS daemons are composed by nfsd, rpc.mountd, rpc.rquotad, rpc.lockd. 1. nfsd: nfsd handles client requests from remote systems. Multiple copies of this daemon are usually run so that several requests can be handled simultaneously. However, too many copies of nfsd […]
CentOS / RHEL : How to configure vsftpd to use ports other than the default ports 20 and 21
Very Secure FTP Daemon (vsftpd) is the most secure and fastest FTP server. By default the vsftp server runs on the port 20 and 21. As a security recommendation, in some organizations system admins tend to change the port from the default ports 20 and 21 to some other ports. The post describes steps to […]
CentOS / RHEL : How to disable ssh for non-root users (allowing ssh only for root user)
By default all users can SSH into a system with a valid password/public key. For certain dedicated Servers with specific roles, such as FTP Server, E-mail Server, etc.; disabling non-root users to login through SSH is usually recommended. The post details out the steps to disable the non-root user ssh login access to systems. There […]
How to block non-root user from creating crontab entry in Linux
The requirement here is that – no non-root user should be allowed to edit the crontab entries. The post describes the steps to do so. There are three ways to achieve this: 1. Disable non-root user ssh to system, which in turn disables shell login itself for a non-root user. 2. Add user name into […]
UNIX / Linux : How to delete root equivalent user (Non-Root User with UID 0)
If you try to delete a user with UID 0 by userdel command, you will get following error. # id uid=0(root) gid=0(root) groups=0(root) # userdel userdel: user user01 is currently used by process 1 All the processes are owned by user IDs and not user-names. So, All process owned by root will be owned by […]
UNIX / Linux : How crontab validates the access based on the cron.allow and cron.deny files
To allow or deny access to specific users, crontab uses the files /etc/cron.allow and /etc/cron.deny. Based on the existence of /etc/cron.allow and /etc/cron.deny files, crontab decides whom to give access to cron in following order. If cron.allow exists – only the users listed in the file cron.allow will get an access to crontab. If cron.allow […]