You don't need to use Samba, AD supports Kerberos and LDAP directly. There is no reason for you to use any external software on most distributions.
For Debian/Ubuntu you can do it with libnss-ldap and libpam-krb5. There are a few tricks to get it 100%. This assumes you have "unixHomeDirectory" populated for Linux users, your Linux boxes are using NTP common with your Windows systems (required by Kerberos) and that you are OK with plain text NSS lookups (not password but group membership info etc - you can also use TLS but that's more complicated to set up). You should NOT have pam_ldap as a password or auth source in PAM unless you are set up to use TLS.
# LDAP Configuration for libnss-ldap and libpam-ldap.
# Permit host to continue boot process with out contacting LDAP server
# Define LDAP servers to use for queries, these must be Global Catalog servers
# Define root search location for queries
# LDAP version, almost always going to be v3, it is quite mature
# Username used to proxy authentication. You can have this in a separate file owned by root for security OR use TLS/SSL (see man page)
# Do NOT use LDAP for authentication if you are using plain text binds, use Kerberos instead (and LDAP for authorization only). See libpam-krb5.
# Password for proxy acct
# TCP port to perform queries on, 3268 is a Global Catalog port which will reply for all users in *.company.local
# Search range scope (sub = all)
# Tell the client to close TCP connctions after 30 seconds, Windows will do this on the server side anyways, this will prevent errors from showing up in the logs.
# Expect queries for group membership to return DN for group members instead of usernames (lets you use MSAD group membership seamlessly)
# Filters - User accounts must have a UID >= 2000 to be recognized in this configuration and must have a unixHomeDirectory defined.
# Object Class mappings. You may want to have the posixAccount to map to "mail" and have users login with their email addresses, i.e. "nss_map_objectclass posixAccount mail".
nss_map_objectclass posixAccount user
nss_map_objectclass shadowAccount user
nss_map_objectclass posixGroup group
# Attribute mappings.
nss_map_attribute uniqueMember member
nss_map_attribute uid sAMAccountName
nss_map_attribute homeDirectory unixHomeDirectory
nss_map_attribute shadowLastChange pwdLastSet
# Attribute in LDAP to query to match the username used by PAM for authentication
# Filter for objects which are allowed to login via PAM
You should not need to edit /etc/krb5.conf assuming your Linux boxes are using DNS servers that know about AD (_msdcs zones with the appropriate SRV records are resolvable)
/etc/nsswitch.conf should have "files ldap" for users, groups, shadow.
For Red Hat using SSSD:
id_provider = ldap
auth_provider = krb5
chpass_provider = krb5
access_provider = ldap
ldap_uri = ldap://ldap.company.local:3268/
ldap_search_base = dc=company,dc=com
ldap_default_bind_dn = cn=ldap-auth-svc,ou=ldap,ou=services,dc=site,dc=company,dc=local
ldap_default_authtok = SooperSekeretPazzwerd
ldap_schema = rfc2307bis
ldap_user_object_class = user
ldap_group_object_class = group
ldap_user_name = sAMAccountName
ldap_user_home_directory = unixHomeDirectory
enumerate = true
ldap_tls_reqcert = never
ldap_tls_cacertdir = /etc/openldap/cacerts
ldap_id_use_start_tls = False
cache_credentials = True
krb5_realm = SITE.COMPANY.COM
case_sensitive = false
services = nss, pam
config_file_version = 2
domains = AD
filter_users = root,named,avahi,nscd