CIT 470: Advanced Network and System Administration Distributing Files CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Topics Sharing Files Copying Files: push vs pull rsync Network Filesystems Administering NFS CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Sharing Files System files Centralize administration: shared logins, naming. Solution: copy files between machines. Alt Solution: Directory services (LDAP.) User files User wants access to files on every machine. Alt Solution: Network filesystems. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Copying Files Advantages No network services to set up. Works everywhere. Decisions Push vs Pull Solutions ftp wget ssh rsync CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Automating ftp #!/usr/bin/expect spawn ftp mysvr.nku.edu expect “username:” send “ftp\r” expect “password:” send “expect@client.nku.edu\r” expect “ftp>” send “bin\r” send “prompt\r” send “mget *\r” send “bye\r” expect eof CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration wget Non-interactive file retrieval Protocols: ftp, http, https. Useful for automating file xfer in scripts. Ex: wget http://svr.nku.edu/files/etc/hosts Options Authentication and proxying. Quiet Recursive: follows links in HTTP documents. Resume Retries CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration ssh-based copying Securely copy files to/from another host. Limitations scp copies list of files on command line (-r for recursive) to single destination. Copies all files, not just updated files. Must share keys to authenticate securely. sftp most suited for manual fs exploration. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration rsync Synchronizes file trees between machines. Advantages Makes remote tree identical to local one. Only copies files that have been changed. Only copies file parts that have been changed. Useful for local mirroring, staging dirs, &c too. Transport Mechanisms rcp: insecure, avoid. scp: secure, commonly used. rsync: rsync protocol, best for anonymous use. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration rsync over ssh Push rsync -av -e ssh local root@svr:test Pull rsync -av -e ssh root@svr:test local Test rsync -avn -e ssh root@svr:test local CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Fine tuning rsync Deleting removed files (be careful) rsync -av -e ssh --delete local root@svr:test Excluding unwanted files. On the command line rsync -av -e ssh --exclude=“*.bak” --exclude=".?*.sw?” local root@svr:test Through a file rsync -av -e ssh --exclude-from=~/exclude-list local root@svr:test CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration rsync server Setting up an rsync server Create an rsyncd.conf file. Server: rsync --daemon Client: rsync svr::public/new.tgz . Simple, but be careful about security. Often secure by DNS name or IP address. Can secure by user with rsync secrets file. No encryption (need to use ssh tunnel.) CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration rsyncd.conf # "global-only" options syslog facility = local5 # global options which may also be defined in modules use chroot = yes uid = nobody gid = nobody max connections = 20 timeout = 600 read only = yes # module: [public] path = /home/rsync comment = Tarball archive hosts allow = *.nku.edu, 10.18.3.0/24, 10.30.4.4 ignore nonreadable = yes refuse options = checksum dont compress = * CIT 470: Advanced Network and System Administration

Other File Distribution Systems rdist Older tool like rsync but slower, fewer features. unison Unlike rsync, handles updates on both sides. Conflict resolution like CVS to handle case when file is modified on both sides. cfengine Maintains state of system according to policy. Copies files as needed to meet policy. CIT 470: Advanced Network and System Administration

Automating File Copying Write a cron job. Script can verify data before/after copy too. How to deal with many machines? Add a random delay using a simple script: #!/usr/bin/perl # sleep 0-15 minutes (0-900s) sleep rand() * 900; CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Network Filesystems Idea: Use filesystem to transparently share files between computers. Solution: Client mounts network fs as normal. Client filesystem code sends packets to server(s). Server responds with data stored on a regular on-disk filesystem. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration NFS Network File System Transparent, behaves like a regular UNIX filesystem. Uses UNIX UIDs,GIDs,perms but can work on Win. Since NFS is stateless, file locking and recovery are handled by rpc.lockd and rpc.statd daemons. Security Server only lets certain IP addresses mount filesystems. Client UIDs have same permissions on server as client. Client root UID is mapped to nobody, but Root can su to any client UID to access any file. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration CIFS Microsoft Network Filesystem Derived from 1980s IBM SMB net filesystem. Originally ran over NetBIOS, not TCP/IP. \\svr\share\path Universal Naming Convention Auth: NTLM (insecure), NTLMv2, Kerberos Implementation MS Windows-centric (filenames, ACLs, EOLs) Samba: UNIX client and server software. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration AFS Distributed filesystem Global namespace: /afs/abc.com/vol_home1 Servers provide one or more volumes. Volume replication with RO copies on other svrs. Cells are administrative domains within AFS. Cells contain multiple servers. Each server provides multiple volumes. Security Kerberos authentication ACLs with user-administered groups CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration NFSv4 New model of NFS Only one protocol (no separate mount,lock,etc.) Global namespace. Security (ACLs, Kerberos, encryption) Cross platform + internationalized. Better caching via delegation of files to clients. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Adminstering NFS NFS Versions Using NFS NFS Services Server and Client Configuration Automounter Security Performance CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration NFS Verions v2 (1984) UDP 32-bit v3 (1992) TCP 64-bit. v4 (2000) Distributed, x-platform, security. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Using NFS Client Start portmap … Mount filesystems. Server Start portmap Start NFS services. Configure exports. Export filesystems. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration NFS Services portmap — RPC service for Linux portmap nfs — NFS file server processes. rpc.mountd rpc.rquotad nfsd nfslock — Optional file locking service. rpc.statd CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration NFSv2/3 Processes rpc.mountd — Handles client mount requests. rpc.nfsd — NFS server processes. rpc.lockd — Process for optional nfslock service. rpc.statd — Handles server crashes for nfslock. rpc.rquotad — Quotas for remote users. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration rpcinfo > rpcinfo -p program vers proto port 100000 2 tcp 111 portmapper 100000 2 udp 111 portmapper 100021 1 udp 32774 nlockmgr 100021 1 tcp 34437 nlockmgr 100011 1 udp 819 rquotad 100011 2 udp 819 rquotad 100011 1 tcp 822 rquotad 100011 2 tcp 822 rquotad 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 100003 2 tcp 2049 nfs 100003 3 tcp 2049 nfs 100005 2 udp 836 mountd 100005 2 tcp 839 mountd 100005 3 udp 836 mountd 100005 3 tcp 839 mountd CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration NFSv4 Processes nfsd — NFSv4 server processes. Handles mounts. rpc.idmapd — Maps NFSv4 names (user@domain) and local UIDs and GIDs. Uses /etc/idmapd.conf. rpc.svcgssd — Server transport Kerberos auth. rpc.gssd — Client transport Kerberos auth. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Server Configuration Configure /etc/exports List filesystems to be exported. Specify export options (ro, rw, etc.) Specify hosts/networks to export to. Export filesystems. exportfs Start NFS server (if not already started) service portmap start service nfs start CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration /etc/exports Format: directory hosts(options) Options ro, rw Read-only, read-write. async Server replies before write. sync Save before reply (default) all_squash Map all users to anon UID/GID. root_squash Map root to anon UID (default) no_root_squash Don’t map root (insecure.) anon{uid,gid} Set anonymous UID, GID. Examples: /home *.example.com(rw,sync) /backups 192.168.1.0/24(ro,all_squash) /ex/limited foo.example.com CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Client Configuration Manual mounting mount -t <nfs-type> -o <options> server:/remote/export /local/directory Mounting via /etc/fstab server:/remote/export /local/directory <nfs-type> <options> 0 0 NFS Type is either nfs or nfs4. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Mount Options hard or soft — Error handling hard: NFS requests will uninterruptible wait until server back. soft: NFS requests will timeout and report failure. intr — NFS requests can be interrupted if server unreachable. nfsvers=2,3— NFS protocol version (not 4) noexec — Prevents execution of binaries. nosuid — Disables setuid for security. rsize,wsize=# — NFS data block size (default 8192) sec=mode — NFS security type. sys uses local UIDs and GIDs. krb5 uses Kerberos5 authentication. krb5i uses Kerberos5 authentication + integrity checking krb5p uses Kerberos5 auth + integrity checking + encryption. tcp, udp — Specifies protocol to use for mount. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Automounter Manages NFS mounts Automounter maps vs /etc/fstab. Mounts filesystems only when needed: Makes administering many filesystems easier. Improves startup speed. Provides uniform namespaces. Ex: mounts /home/home7 as /home on login. /etc/auto.master points to maps /home /etc/auto.home Maps describe mounts * -fstype=nfs4,soft,intr,nosuid server:/home CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Security Limit which hosts have access to filesystems. Specify hosts in /etc/exports. Use iptables to limit which hosts can use NFS. Limit mount options Default to ro unless writes are necessary. Disable suid and execution unless needed. Map root to nobody. Block NFS at network firewalls. Block all protocols, not just port 2049. Use NFSv4 with Kerberos auth + encryption. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration Performance Measuring performance nfsstat /proc/net/rpc/nfsd Optimizations Increase the block size. Problem: fragments? Set the async option on mounts. Faster network card. Faster disk array. NVRAM cache on array to save NFS writes. CIT 470: Advanced Network and System Administration

CIT 470: Advanced Network and System Administration References Michael D. Bauer, Linux Server Security, 2nd edition, O’Reilly, 2005. cfengine, http://www.cfengine.org/ Mike Eisler, Ricardo Labiaga, Hal Stern, Managing NFS and NIS, 2nd edition, O’Reilly, 2001. expect, http://expect.nist.gov/ Aeleen Frisch, Essential System Administration, 3rd edition, O’Reilly, 2002. Evi Nemeth et al, UNIX System Administration Handbook, 3rd edition, Prentice Hall, 2001. NFS HOWTO, http://nfs.sourceforge.net/nfs-howto RedHat, Red Hat Enterprise Linux 4 System Administration Guide, http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/sysadmin-guide/, 2005. RedHat, Red Hat Enterprise Linux 4 Reference Guide, http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/ref-guide/ch-nfs.html, 2005. rsync, http://www.samba.org/rsync/ Unison, http://www.cis.upenn.edu/~bcpierce/unison/ CIT 470: Advanced Network and System Administration