RHEL 7 – RHCSA Notes (Cheat Sheets) SELinux modes SELinux gives that extra layer of security to the resources in the system. It provides the MAC (mandatory access control) as contrary to the DAC (Discretionary access control). Before we dive into setting the SELinux modes, let us see what are the different SELinux modes of operation and how do they work. SELinux can operate in any of the 3 modes : 1. Enforced : Actions contrary to the policy are blocked and a corresponding event is logged … [Read more...] about RHEL 7 – RHCSA Notes – Set enforcing and permissive modes for SELinux
Archives for September 2016
RHEL 7 – RHCSA Notes – Create and manage Access Control Lists (ACLs)
RHEL 7 – RHCSA Notes (Cheat Sheets) The file access control lists (FACLs) or simply ACLs are the list of additional user/groups and their permission to the file. Although the default file permissions does their jobs perfectly, it does not allow you to give permissions to more than one user or one group on the same file. How to know when a file has ACL attached to it ls -l command would produce a output as show below. Note the + sign at the end of the permissions. This confirms that the … [Read more...] about RHEL 7 – RHCSA Notes – Create and manage Access Control Lists (ACLs)
CentOS / RHEL : How to change password hashing algorithm
authconfig The Linux user password hashing algorithm is also configurable. Use the authconfig command to determine the current algorithm being used, or to set it to something different. To determine the current algorithm: # authconfig --test | grep hashing password hashing algorithm is sha512 Change the hashing algorithm To change the algorithm, use the --passalgo option with one of the following as a parameter: descrypt, bigcrypt, md5, sha256, or sha512, followed by the --update … [Read more...] about CentOS / RHEL : How to change password hashing algorithm
RHEL 7 – RHCSA Notes : Change passwords and adjust password aging for local user accounts
RHEL 7 – RHCSA Notes (Cheat Sheets) Password configuration password aging requires users to change their password periodically. Use the chage to configure password expiration. The syntax is : # chage [options] user_name - When you fire the command chage, the currently set options are displayed as well. # chage oracle Changing the aging information for oracle Enter the new value, or press ENTER for the default Minimum Password Age [14]: Maximum Password Age [30]: Last Password … [Read more...] about RHEL 7 – RHCSA Notes : Change passwords and adjust password aging for local user accounts
Solaris zones : How to set netmasks
Question : How to set certain netmask for a non global zone ? Answer : To define a certain netmask for a non global zone, use zonecfg command. The network address is one of: a valid IPv4 address, optionally followed by "/" and a prefix length. a valid IPv6 address, which must be followed by "/" and a prefix length. Steps to follow 1. On the global zone, enter the zone configuration mode : global_zone # zonecfg -z zone01 zonecfg:zone01> add net … [Read more...] about Solaris zones : How to set netmasks
CentOS / RHEL : How to assemble a software RAID in Rescue mode
mdadm (multiple devices admin) is an extremely useful tool for running RAID systems. It’s is a tool for creating, managing, and monitoring RAID devices using the md driver. It can be used as a replacement for the raidtools, or as a supplement. The pos describes a way to assemble a software RAID in rescue mode. 1. Boot into rescue mode. 2. First create the mdadm.conf file with the disks available # mdadm --examine --scan >> /etc/mdadm.conf 3. Assemble the array # mdadm --assemble … [Read more...] about CentOS / RHEL : How to assemble a software RAID in Rescue mode
Solaris 11.2 : Adding new resources to a running zone online
Solaris 11.2 provides a supported way to add new resources to a running zone online. Prior to this version, a reboot of the non-global zone was required to make the changes effective. The post describes an example of adding a raw disk device online to a non-global zone. Example: 1. Check the Solaris OS version. # uname -a SunOS test 5.11 11.2 sun4v sparc SUNW,T5240 2. List the zones available on the system. In our example we will be adding disk resource to the zone - zone01 # zoneadm … [Read more...] about Solaris 11.2 : Adding new resources to a running zone online
Examples of using vxdiskunsetup command
- vxdiskunsetup command is used to remove the vxvm configuration from the disk. Its works the opposite way of the command vxdisksetup. - vxdiskunsetup command remove the public and private regions created by the command vxdisksetup command. - vxdiskunsetup command turns the disk flags from online to error. check the options available in the vxdiskunsetup command : # /etc/vx/bin/vxdiskunsetup -h VxVM vxdiskunsetup INFO V-5-2-6407 vxdiskunsetup - remove a disk from use by the volume … [Read more...] about Examples of using vxdiskunsetup command
RHEL 7 – RHCSA Notes : Create, delete, and modify local groups and group memberships.
RHEL 7 – RHCSA Notes (Cheat Sheets) Group administration - Use the groupadd command to add a new group : # groupadd [options] group_name - Use the groupmod command to modify an existing group : # groupmod [options] group_name - Use groupdel to delete the group. You can remove a group even if there are users in the group. But you can not remove the primary group of an existing user. You must remove the user before removing the group. # groupdel group_name - Use the gpasswd command to … [Read more...] about RHEL 7 – RHCSA Notes : Create, delete, and modify local groups and group memberships.
RHEL 7 – RHCSA Notes : Create, delete, and modify local user accounts
RHEL 7 – RHCSA Notes (Cheat Sheets) Adding a user account Use the useradd command to add new user : # useradd [options] [username] The default settings for new user can viewed and modified using the -D option : # useradd -D GROUP=100 HOME=/home INACTIVE=-1 EXPIRE= SHELL=/bin/bash SKEL=/etc/skel CREATE_MAIL_SPOOL=yes For example, to change the default user shell for new user to /bin/ksh : # useradd -D -s /bin/ksh Examples To simple add a user with all default options : # … [Read more...] about RHEL 7 – RHCSA Notes : Create, delete, and modify local user accounts