NotesByLex

Red Hat System Administration III - Unit 1 - RCSHA Review

Lex Toumbourou ·

Linux

RPM

  • Tarball with metadata (where files go, permissions, SELinux etc).

ISET rule

  • Install
  • Start
  • Enable
  • Test

Virtualization Review

# virsh list
 Id    Name                           State
----------------------------------------------------
 1     vserver                        running

# virsh list --all
 Id    Name                           State
----------------------------------------------------
 1     vserver                        running

# virsh start vserver
# virsh destroy vserver
# virsh console vserver

Single-user mode

  • Bypass the root password

  • How to get into single-user mode:

    > init 1

  • Append argument to kernel command at boot (s or 1 or single)

Users

  • local
    • /etc/passwd: <uname>:<passwd>:<uid>:<gid>:<comment>:<home_dir>:<shell>
    • /etc/shadow
    • hash: $<hash_type>$<salt>$<hash>
  • network
    • centralised management (LDAP etc)

Package Group install

yum groupinstall "directory-client"

LDAP

  • Need 3 things:
    • LDAP Server's FQDN
      • Base DN - top of the tree.
        • Used to search for LDAP entries (user, group info)
    • CA Cert
    • Config LDAP with system-config-authentication
  • Use getent to query LDAP:
# getent passwd ldapuser1
ldapuser1:x:1701:1701:LDAP Test User 1:/home/guests/ldapuser1:/bin/bash
  • autofs is used to automount shares for LDAP users
    • auto.master -> master config file for autofs
      • 3 things needed:
        • server name
        • exported share
        • local mount point
  • mount options:
    • showmount is used to query NFS servers for shares:
# showmount -e instructor.example.com
Export list for instructor.example.com:
/home/guests 192.168.0.0/255.255.255.0
/var/nfs     192.168.1.0/255.255.255.0,192.168.0.0/255.255.255.0
/kickstart   192.168.1.0/255.255.255.0,192.168.0.0/255.255.255.0
/var/ftp/pub 192.168.1.0/255.255.255.0,192.168.0.0/255.255.255.0
  • service autofs reload after updating auto.guests

SSH

  • ssh -X user@servername
    • -X sets X-forwarding enabled
  • Public key of remote machine stored locally under ~/.ssh/known_hosts
  • /etc/ssh/sshd_config commands:
    • Set PermitRootLogin = no to deny root login
    • Set PasswordAuthentication = no to deny password authentication