233 lines
8.3 KiB
Markdown
233 lines
8.3 KiB
Markdown
### WHAT IS IT?
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NsJail is a process isolation tool for Linux. It makes use of the the namespacing, resource control, and seccomp-bpf syscall filter subsystems of the Linux kernel.
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It can help, among others, with:
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* Securing networking services (e.g. web, time, DNS), by isolating them from the rest of the OS
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* Hosting computer security challenges (so-called CTFs)
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* Containing invasive syscall-level OS fuzzers
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This is NOT an official Google product.
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### WHAT KIND OF ISOLATION DOES THIS TOOL PROVIDE?
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1. Linux namespaces: UTS (hostname), MOUNT (chroot), PID (separate PID tree), IPC, NET (separate networking context), USER
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2. FS constraints: chroot(), pivot_root(), RO-remounting
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3. Resource limits (wall-time/CPU time limits, VM/mem address space limits, etc.)
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4. Programmable seccomp-bpf syscall filters
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5. Cloned and separated Ethernet interfaces
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### WHAT KIND OF USE-CASES ARE SUPPORTED?
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#### Isolation of network services (inetd-style)
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+ Server:
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```
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$ ./nsjail -Ml --port 9000 --chroot /chroot/ --user 99999 --group 99999 -- /bin/sh -i
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```
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+ Client:
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```
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$ nc 127.0.0.1 9000
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/ $ ifconfig
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/ $ ifconfig -a
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lo Link encap:Local Loopback
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LOOPBACK MTU:65536 Metric:1
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RX packets:0 errors:0 dropped:0 overruns:0 frame:0
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TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0
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RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
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/ $ ps wuax
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PID USER COMMAND
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1 99999 /bin/sh -i
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3 99999 {busybox} ps wuax
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/ $
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```
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#### Isolation, with access to a private, cloned interface (requires euid==0)
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```
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$ sudo ./nsjail --user 9999 --group 9999 --iface eth0 --chroot /chroot/ -Mo --iface_vs_ip 192.168.0.44 --iface_vs_nm 255.255.255.0 --iface_vs_gw 192.168.0.1 -- /bin/sh -i
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/ $ id
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uid=9999 gid=9999
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/ $ ip addr sh
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1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue
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link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
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inet 127.0.0.1/8 scope host lo
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valid_lft forever preferred_lft forever
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inet6 ::1/128 scope host
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valid_lft forever preferred_lft forever
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2: vs: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
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link/ether ca:a2:69:21:33:66 brd ff:ff:ff:ff:ff:ff
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inet 192.168.0.44/24 brd 192.168.0.255 scope global vs
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valid_lft forever preferred_lft forever
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inet6 fe80::c8a2:69ff:fe21:cd66/64 scope link
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valid_lft forever preferred_lft forever
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/ $ nc 217.146.165.209 80
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GET / HTTP/1.0
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HTTP/1.0 302 Found
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Cache-Control: private
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Content-Type: text/html; charset=UTF-8
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Location: http://www.google.ch/?gfe_rd=cr&ei=cEzWVrG2CeTI8ge88ofwDA
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Content-Length: 258
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Date: Wed, 02 Mar 2016 02:14:08 GMT
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<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">
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<TITLE>302 Moved</TITLE></HEAD><BODY>
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<H1>302 Moved</H1>
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The document has moved
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<A HREF="http://www.google.ch/?gfe_rd=cr&ei=cEzWVrG2CeTI8ge88ofwDA">here</A>.
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</BODY></HTML>
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/ $
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```
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#### Isolation of local processes
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```
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$ ./nsjail -Mo --chroot /chroot/ --user 99999 --group 99999 -- /bin/sh -i
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/ $ ifconfig -a
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lo Link encap:Local Loopback
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LOOPBACK MTU:65536 Metric:1
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RX packets:0 errors:0 dropped:0 overruns:0 frame:0
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TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0
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RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
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/ $ id
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uid=99999 gid=99999
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/ $ ps wuax
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PID USER COMMAND
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1 99999 /bin/sh -i
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4 99999 {busybox} ps wuax
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/ $exit
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$
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```
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#### Isolation of local processes (and re-running them)
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```
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$ ./nsjail -Mr --chroot /chroot/ --user 99999 --group 99999 -- /bin/sh -i
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BusyBox v1.21.1 (Ubuntu 1:1.21.0-1ubuntu1) built-in shell (ash)
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Enter 'help' for a list of built-in commands.
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/ $ ps wuax
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PID USER COMMAND
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1 99999 /bin/sh -i
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2 99999 {busybox} ps wuax
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/ $ exit
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BusyBox v1.21.1 (Ubuntu 1:1.21.0-1ubuntu1) built-in shell (ash)
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Enter 'help' for a list of built-in commands.
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/ $ ps wuax
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PID USER COMMAND
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1 99999 /bin/sh -i
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2 99999 {busybox} ps wuax
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/ $
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```
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### MORE INFO?
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Type:
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```
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./nsjail --help'
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```
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The commandline options are reasonably well-documented
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```
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Usage: ./nsjail [options] -- path_to_command [args]
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Options:
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--help|-h
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Help plz..
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--mode|-M [val]
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Execution mode (default: l [MODE_LISTEN_TCP]):
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l: Wait for connections on a TCP port (specified with --port) [MODE_LISTEN_TCP]
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o: Immediately launch a single process on a console using clone/execve [MODE_STANDALONE_ONCE]
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e: Immediately launch a single process on a console using execve [MODE_STANDALONE_EXECVE]
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r: Immediately launch a single process on a console, keep doing it forever [MODE_STANDALONE_RERUN]
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--cmd
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Equivalent of -Mo (MODE_STANDALONE_ONCE), run command on a local console, once
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--chroot|-c [val]
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Directory containing / of the jail (default: "/"). Skip mounting it if ""
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--rw
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Mount / as RW (default: RO)
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--user|-u [val]
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Username/uid of processess inside the jail (default: your current uid). You can also use inside_ns_uid:outside_ns_uid convention here
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--group|-g [val]
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Groupname/gid of processess inside the jail (default: your current gid). You can also use inside_ns_gid:global_ns_gid convention here
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--hostname|-H [val]
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UTS name (hostname) of the jail (default: 'NSJAIL')
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--cwd|-D [val]
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Directory in the namespace the process will run (default: '/')
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--port|-p [val]
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TCP port to bind to (only in [MODE_LISTEN_TCP]) (default: 31337)
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--bindhost [val]
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IP address port to bind to (only in [MODE_LISTEN_TCP]) (default: '::')
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--max_conns_per_ip|-i [val]
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Maximum number of connections per one IP (default: 0 (unlimited))
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--log|-l [val]
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Log file (default: /proc/self/fd/2)
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--time_limit|-t [val]
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Maximum time that a jail can exist, in seconds (default: 600)
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--daemon|-d
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Daemonize after start
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--verbose|-v
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Verbose output
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--keep_env|-e
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Should all environment variables be passed to the child?
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--env|-E [val]
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Environment variable (can be used multiple times)
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--keep_caps
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Don't drop capabilities (DANGEROUS)
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--silent
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Redirect child's fd:0/1/2 to /dev/null
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--disable_sandbox
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Don't enable the seccomp-bpf sandboxing
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--skip_setsid
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Don't call setsid(), allows for terminal signal handling in the sandboxed process
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--rlimit_as [val]
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RLIMIT_AS in MB, 'max' for RLIM_INFINITY, 'def' for the current value (default: 512)
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--rlimit_core [val]
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RLIMIT_CORE in MB, 'max' for RLIM_INFINITY, 'def' for the current value (default: 0)
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--rlimit_cpu [val]
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RLIMIT_CPU, 'max' for RLIM_INFINITY, 'def' for the current value (default: 600)
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--rlimit_fsize [val]
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RLIMIT_FSIZE in MB, 'max' for RLIM_INFINITY, 'def' for the current value (default: 1)
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--rlimit_nofile [val]
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RLIMIT_NOFILE, 'max' for RLIM_INFINITY, 'def' for the current value (default: 32)
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--rlimit_nproc [val]
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RLIMIT_NPROC, 'max' for RLIM_INFINITY, 'def' for the current value (default: 'def')
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--rlimit_stack [val]
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RLIMIT_STACK in MB, 'max' for RLIM_INFINITY, 'def' for the current value (default: 'def')
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--persona_addr_compat_layout
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personality(ADDR_COMPAT_LAYOUT)
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--persona_mmap_page_zero
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personality(MMAP_PAGE_ZERO)
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--persona_read_implies_exec
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personality(READ_IMPLIES_EXEC)
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--persona_addr_limit_3gb
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personality(ADDR_LIMIT_3GB)
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--persona_addr_no_randomize
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personality(ADDR_NO_RANDOMIZE)
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--disable_clone_newnet|-N
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Don't use CLONE_NEWNET. Enable networking inside the jail
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--disable_clone_newuser
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Don't use CLONE_NEWUSER. Requires euid==0
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--disable_clone_newns
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Don't use CLONE_NEWNS
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--disable_clone_newpid
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Don't use CLONE_NEWPID
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--disable_clone_newipc
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Don't use CLONE_NEWIPC
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--disable_clone_newuts
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Don't use CLONE_NEWUTS
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--bindmount_ro|-R [val]
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List of mountpoints to be mounted --bind (ro) inside the container. Can be specified multiple times. Supports 'source' syntax, or 'source:dest'
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--bindmount|-B [val]
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List of mountpoints to be mounted --bind (rw) inside the container. Can be specified multiple times. Supports 'source' syntax, or 'source:dest'
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--tmpfsmount|-T [val]
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List of mountpoints to be mounted as RW/tmpfs inside the container. Can be specified multiple times. Supports 'dest' syntax
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--tmpfs_size [val]
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Number of bytes to allocate for tmpfsmounts (default: 4194304)
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--disable_proc
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Disable mounting /proc in the jail
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--iface_no_lo
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Don't bring up the 'lo' interface
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--iface|-I [val]
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Interface which will be cloned (MACVTAP) and put inside the subprocess' namespace as 'vs'
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--iface_vs_ip [val]
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IP of the 'vs' interface
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--iface_vs_nm [val]
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Netmask of the 'vs' interface
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--iface_vs_gw [val]
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Default GW for the 'vs' interface
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```
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